Forecast Discussion - NOAA's National Weather Service

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000
FXUS63 KILX 151703
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1103 AM CST THU JAN 15 2009

.DISCUSSION...
ISSUED 1035 AM CST THU JAN 15 2009

TEMPS NOT CLIMBING AS EXPECTED...ESPECIALLY OVER THE SNOW PACK
AREAS. THEREFORE...WILL BE UPDATING TEMPS FOR THIS AFTERNOON.
AREAS SOUTH OF THE SNOW IS WARMING AND ARE ABOVE ZERO. WILL LIKELY
SEE A TIGHT TEMP GRADIENT THIS AFTERNOON. TEMPS TONIGHT COULD BE
COLDER THAN FORECAST AS WELL...SO WILL TAKE A LOOK AT THAT TOO AND
MAY UPDATE THEM AS WELL. REMAINDER OF FCST FOR SKY COVER AND WINDS
LOOKS FINE. WILL ALSO BE KEEPING WIND CHILL WARNING/ADVISORY GOING
THROUGH THE PERIOD.

UPDATE OUT SHORTLY.

AUTEN
&&

.AVIATION...
ISSUED 1103 AM CST THU JAN 15 2009

VFR CONDITIONS EXPECTED THROUGH THE PERIOD AT ALL TAF SITES. SKIES
SHOULD REMAIN CLEAR THE REST OF THE DAY AND INTO TONIGHT...THEN COULD
BE SOME SCT-BKN CIRRUS TOMORROW MORNING. WESTERLY WINDS WILL
CONTINUE TODAY AND BECOME LIGHT OVERNIGHT AS THE RIDGE MOVES INTO
THE AREA. SOUTHERLY WINDS NOT EXPECTED UNTIL NEAR END OF TAF TIME
TOMORROW.

AUTEN
&&

.PREV DISCUSSION...
ISSUED 205 AM CST THU JAN 15 2009

ARCTIC AIRMASS AGGRESSIVELY SPREADING ACROSS CENTRAL AND SOUTHEAST
ILLINOIS OVERNIGHT. UPSTREAM WIND CHILLS WERE IN THE 40S BELOW
ACROSS MANY PARTS OF IOWA...WITH AIR TEMPERATURES CLOSE TO 20
BELOW. TEMPERATURES IN THE NORTHWEST CWA HAD ALREADY PLUNGED TO
NEAR 15 BELOW BY 2 AM...WITH THE ZERO DEGREE LINE AS FAR SOUTH AS
I-70. WIND CHILLS BELOW THE -25F WARNING CRITERIA WERE IN MANY
AREAS NORTH OF A MACOMB TO BLOOMINGTON LINE...AND WERE IN THE
TEENS TO LOWER 20S BELOW ACROSS THE REMAINDER OF CENTRAL ILLINOIS.

TEMPERATURES AND WIND CHILLS THROUGH TOMORROW MORNING ARE THE PRIMARY
CONCERN WITH THIS FORECAST PACKAGE...FOLLOWED BY POTENTIAL EFFECTS
OF CLIPPER SYSTEM OVER THE WEEKEND.

SHORT TERM...TODAY THROUGH SATURDAY...

CENTER OF ARCTIC HIGH WAS OVER THE DAKOTAS EARLY THIS MORNING...AND
THIS IS EXPECTED TO SINK SOUTHEAST INTO MISSOURI TONIGHT. ENOUGH
OF A PRESSURE GRADIENT WILL REMAIN IN PLACE TO KEEP WINDS IN THE
10-15 MPH RANGE. TEMPERATURES EXPECTED TO CONTINUE FALLING FOR A
FEW HOURS AFTER SUNRISE BEFORE ATTEMPTING A COMEBACK...BUT MOST
LOCATIONS NORTH OF I-72 WILL REMAIN BELOW ZERO TODAY. MORNING WIND
CHILLS OF 30-40 BELOW ACROSS THE NORTH WILL ONLY SLIGHTLY RISE
THIS AFTERNOON. NORTHERN HALF OF THE EXISTING WIND CHILL ADVISORY
AREA...GENERALLY BETWEEN I-72 AND I-70...WILL LIKELY SEE WIND
CHILLS BELOW -25F FOR A COUPLE HOURS THIS MORNING...BUT WILL NOT
EXPAND THE WIND CHILL WARNING SOUTHWARD DUE TO THE SHORT DURATION
OF THIS THRESHOLD VALUE.

WINDS EXPECTED TO TAPER OFF OVERNIGHT AS THE HIGH MOVES INTO THE
OHIO VALLEY. HOWEVER...WITH AIR TEMPERATURES OF 10 TO 20 BELOW
ZERO ACROSS THE NORTH HALF OF THE CWA...THE EXTREME WIND CHILLS
WILL CONTINUE OVERNIGHT. SOUTH HALF OF THE CWA EXPECTED TO HAVE
WIND CHILLS OF 15 TO 25 BELOW CONTINUING.

WARM AIR ADVECTION FINALLY BEGINS TO SET UP FRIDAY AFTERNOON AS
THE HIGH SINKS FURTHER TOWARD THE SOUTHEAST. DECENT DIURNAL SWING
IN TEMPERATURES EXPECTED AS HIGHS REACH INTO THE TEENS FRIDAY
AFTERNOON. NOT MUCH DECLINE IS EXPECTED FRIDAY NIGHT AS BRISK
SOUTHERLY FLOW CONTINUES.

NEXT CLIPPER SYSTEM WILL DIVE SOUTHEAST INTO THE WESTERN GREAT
LAKES REGION BY SATURDAY MORNING. NAM-WRF THE ODD MODEL OUT IN
TRACKING THE SYSTEM MUCH FURTHER WEST ACROSS THE DAKOTAS INTO
WESTERN IOWA...SO ITS SOLUTION WAS DISCOUNTED. THE ECMWF/GFS AND
CANADIAN MODELS MORE UNIFORM IN THE TRACK OF THIS SYSTEM WITH LOW
PRESSURE MOVING FROM NEAR MINNEAPOLIS TO DETROIT...WITH ITS
TRAILING COLD FRONT SWEEPING ACROSS ILLINOIS. MOISTURE IS RATHER
MEAGER WITH THIS SYSTEM AND IS CURRENTLY EXPECTED TO BE LIMITED
TO AREAS CLOSER TO THE LOW TRACK. KEPT LOW CHANCE POPS GOING
ACROSS THE NORTHERN EDGE OF THE FORECAST AREA...PRIMARILY LATE
FRIDAY NIGHT INTO SATURDAY MORNING. TEMPERATURES EXPECTED TO MAKE
A DECENT RECOVERY DESPITE THE PASSAGE OF THE BOUNDARY...ALTHOUGH
STILL REMAINING A BIT BELOW NORMAL FOR MID JANUARY.

LONG TERM...SUNDAY THROUGH WEDNESDAY...

NO CHANGES WERE MADE TO THIS PART OF THE FORECAST. PERSISTENT
UPPER PATTERN OF RIDGE WEST/TROUGH EAST EXPECTED TO CONTINUE
ACROSS THE NATION INTO EARLY NEXT WEEK...AS THE RIDGE SLOWLY
BEGINS TO BREAK DOWN. MORE MODERATION IN TEMPERATURES IS EXPECTED
AS FLOW TRIES TO BECOME MORE ZONAL.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 12 PM CST FRIDAY FOR ILZ049>057-
061>063-066>068-071>073.

WIND CHILL WARNING UNTIL 12 PM CST FRIDAY FOR ILZ027>031-036>038-
040>048.

&&

$$


000
FXUS63 KILX 151635
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1035 AM CST THU JAN 15 2009

.DISCUSSION...
ISSUED 1035 AM CST THU JAN 15 2009

TEMPS NOT CLIMBING AS EXPECTED...ESPECIALLY OVER THE SNOW PACK
AREAS. THEREFORE...WILL BE UPDATING TEMPS FOR THIS AFTERNOON.
AREAS SOUTH OF THE SNOW IS WARMING AND ARE ABOVE ZERO. WILL LIKELY
SEE A TIGHT TEMP GRADIENT THIS AFTERNOON. TEMPS TONIGHT COULD BE
COLDER THAN FORECAST AS WELL...SO WILL TAKE A LOOK AT THAT TOO AND
MAY UPDATE THEM AS WELL. REMAINDER OF FCST FOR SKY COVER AND WINDS
LOOKS FINE. WILL ALSO BE KEEPING WIND CHILL WARNING/ADVISORY GOING
THROUGH THE PERIOD.

UPDATE OUT SHORTLY.

AUTEN
&&

.AVIATION...
ISSUED 535 AM CST THU JAN 15 2009

ARCTIC HIGH PRESSURE WILL SETTLE SOUTHEAST ACROSS THE MIDWEST
TODAY WHICH WILL CONTINUE TO BRING VFR CONDITIONS TO THE AREA
THRU THE PERIOD. FORECAST SOUNDINGS SHOWING THE PSBLTY OF
THE DVLPMT OF FEW-SCT STRATOCU ARND 1500 FEET LATER THIS MRNG.
SFC WNDS WL REMAIN OUT OF THE NORTHWEST TODAY WITH FORECAST
SOUNDINGS AND UPSTREAM PROFILERS/ACARS SUGGESTING THE PSBLTY
OF A FEW GUSTS ARND 20 KTS LATER THIS MRNG INTO THE AFTN HOURS.
WINDS SHOULD DROP OFF TO 5 KTS OR LESS THIS EVENING.

SMITH
&&

.PREV DISCUSSION...
ISSUED 205 AM CST THU JAN 15 2009

ARCTIC AIRMASS AGGRESSIVELY SPREADING ACROSS CENTRAL AND SOUTHEAST
ILLINOIS OVERNIGHT. UPSTREAM WIND CHILLS WERE IN THE 40S BELOW
ACROSS MANY PARTS OF IOWA...WITH AIR TEMPERATURES CLOSE TO 20
BELOW. TEMPERATURES IN THE NORTHWEST CWA HAD ALREADY PLUNGED TO
NEAR 15 BELOW BY 2 AM...WITH THE ZERO DEGREE LINE AS FAR SOUTH AS
I-70. WIND CHILLS BELOW THE -25F WARNING CRITERIA WERE IN MANY
AREAS NORTH OF A MACOMB TO BLOOMINGTON LINE...AND WERE IN THE
TEENS TO LOWER 20S BELOW ACROSS THE REMAINDER OF CENTRAL ILLINOIS.

TEMPERATURES AND WIND CHILLS THROUGH TOMORROW MORNING ARE THE PRIMARY
CONCERN WITH THIS FORECAST PACKAGE...FOLLOWED BY POTENTIAL EFFECTS
OF CLIPPER SYSTEM OVER THE WEEKEND.

SHORT TERM...TODAY THROUGH SATURDAY...

CENTER OF ARCTIC HIGH WAS OVER THE DAKOTAS EARLY THIS MORNING...AND
THIS IS EXPECTED TO SINK SOUTHEAST INTO MISSOURI TONIGHT. ENOUGH
OF A PRESSURE GRADIENT WILL REMAIN IN PLACE TO KEEP WINDS IN THE
10-15 MPH RANGE. TEMPERATURES EXPECTED TO CONTINUE FALLING FOR A
FEW HOURS AFTER SUNRISE BEFORE ATTEMPTING A COMEBACK...BUT MOST
LOCATIONS NORTH OF I-72 WILL REMAIN BELOW ZERO TODAY. MORNING WIND
CHILLS OF 30-40 BELOW ACROSS THE NORTH WILL ONLY SLIGHTLY RISE
THIS AFTERNOON. NORTHERN HALF OF THE EXISTING WIND CHILL ADVISORY
AREA...GENERALLY BETWEEN I-72 AND I-70...WILL LIKELY SEE WIND
CHILLS BELOW -25F FOR A COUPLE HOURS THIS MORNING...BUT WILL NOT
EXPAND THE WIND CHILL WARNING SOUTHWARD DUE TO THE SHORT DURATION
OF THIS THRESHOLD VALUE.

WINDS EXPECTED TO TAPER OFF OVERNIGHT AS THE HIGH MOVES INTO THE
OHIO VALLEY. HOWEVER...WITH AIR TEMPERATURES OF 10 TO 20 BELOW
ZERO ACROSS THE NORTH HALF OF THE CWA...THE EXTREME WIND CHILLS
WILL CONTINUE OVERNIGHT. SOUTH HALF OF THE CWA EXPECTED TO HAVE
WIND CHILLS OF 15 TO 25 BELOW CONTINUING.

WARM AIR ADVECTION FINALLY BEGINS TO SET UP FRIDAY AFTERNOON AS
THE HIGH SINKS FURTHER TOWARD THE SOUTHEAST. DECENT DIURNAL SWING
IN TEMPERATURES EXPECTED AS HIGHS REACH INTO THE TEENS FRIDAY
AFTERNOON. NOT MUCH DECLINE IS EXPECTED FRIDAY NIGHT AS BRISK
SOUTHERLY FLOW CONTINUES.

NEXT CLIPPER SYSTEM WILL DIVE SOUTHEAST INTO THE WESTERN GREAT
LAKES REGION BY SATURDAY MORNING. NAM-WRF THE ODD MODEL OUT IN
TRACKING THE SYSTEM MUCH FURTHER WEST ACROSS THE DAKOTAS INTO
WESTERN IOWA...SO ITS SOLUTION WAS DISCOUNTED. THE ECMWF/GFS AND
CANADIAN MODELS MORE UNIFORM IN THE TRACK OF THIS SYSTEM WITH LOW
PRESSURE MOVING FROM NEAR MINNEAPOLIS TO DETROIT...WITH ITS
TRAILING COLD FRONT SWEEPING ACROSS ILLINOIS. MOISTURE IS RATHER
MEAGER WITH THIS SYSTEM AND IS CURRENTLY EXPECTED TO BE LIMITED
TO AREAS CLOSER TO THE LOW TRACK. KEPT LOW CHANCE POPS GOING
ACROSS THE NORTHERN EDGE OF THE FORECAST AREA...PRIMARILY LATE
FRIDAY NIGHT INTO SATURDAY MORNING. TEMPERATURES EXPECTED TO MAKE
A DECENT RECOVERY DESPITE THE PASSAGE OF THE BOUNDARY...ALTHOUGH
STILL REMAINING A BIT BELOW NORMAL FOR MID JANUARY.

LONG TERM...SUNDAY THROUGH WEDNESDAY...

NO CHANGES WERE MADE TO THIS PART OF THE FORECAST. PERSISTENT
UPPER PATTERN OF RIDGE WEST/TROUGH EAST EXPECTED TO CONTINUE
ACROSS THE NATION INTO EARLY NEXT WEEK...AS THE RIDGE SLOWLY
BEGINS TO BREAK DOWN. MORE MODERATION IN TEMPERATURES IS EXPECTED
AS FLOW TRIES TO BECOME MORE ZONAL.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 12 PM CST FRIDAY FOR ILZ049>057-
061>063-066>068-071>073.

WIND CHILL WARNING UNTIL 12 PM CST FRIDAY FOR ILZ027>031-036>038-
040>048.

&&

$$


000
FXUS63 KILX 151150
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
550 AM CST THU JAN 15 2009

.DISCUSSION...
ISSUED 205 AM CST THU JAN 15 2009

ARCTIC AIRMASS AGGRESSIVELY SPREADING ACROSS CENTRAL AND SOUTHEAST
ILLINOIS OVERNIGHT. UPSTREAM WIND CHILLS WERE IN THE 40S BELOW
ACROSS MANY PARTS OF IOWA...WITH AIR TEMPERATURES CLOSE TO 20
BELOW. TEMPERATURES IN THE NORTHWEST CWA HAD ALREADY PLUNGED TO
NEAR 15 BELOW BY 2 AM...WITH THE ZERO DEGREE LINE AS FAR SOUTH AS
I-70. WIND CHILLS BELOW THE -25F WARNING CRITERIA WERE IN MANY
AREAS NORTH OF A MACOMB TO BLOOMINGTON LINE...AND WERE IN THE
TEENS TO LOWER 20S BELOW ACROSS THE REMAINDER OF CENTRAL ILLINOIS.

TEMPERATURES AND WIND CHILLS THROUGH TOMORROW MORNING ARE THE PRIMARY
CONCERN WITH THIS FORECAST PACKAGE...FOLLOWED BY POTENTIAL EFFECTS
OF CLIPPER SYSTEM OVER THE WEEKEND.

SHORT TERM...TODAY THROUGH SATURDAY...

CENTER OF ARCTIC HIGH WAS OVER THE DAKOTAS EARLY THIS MORNING...AND
THIS IS EXPECTED TO SINK SOUTHEAST INTO MISSOURI TONIGHT. ENOUGH
OF A PRESSURE GRADIENT WILL REMAIN IN PLACE TO KEEP WINDS IN THE
10-15 MPH RANGE. TEMPERATURES EXPECTED TO CONTINUE FALLING FOR A
FEW HOURS AFTER SUNRISE BEFORE ATTEMPTING A COMEBACK...BUT MOST
LOCATIONS NORTH OF I-72 WILL REMAIN BELOW ZERO TODAY. MORNING WIND
CHILLS OF 30-40 BELOW ACROSS THE NORTH WILL ONLY SLIGHTLY RISE
THIS AFTERNOON. NORTHERN HALF OF THE EXISTING WIND CHILL ADVISORY
AREA...GENERALLY BETWEEN I-72 AND I-70...WILL LIKELY SEE WIND
CHILLS BELOW -25F FOR A COUPLE HOURS THIS MORNING...BUT WILL NOT
EXPAND THE WIND CHILL WARNING SOUTHWARD DUE TO THE SHORT DURATION
OF THIS THRESHOLD VALUE.

WINDS EXPECTED TO TAPER OFF OVERNIGHT AS THE HIGH MOVES INTO THE
OHIO VALLEY. HOWEVER...WITH AIR TEMPERATURES OF 10 TO 20 BELOW
ZERO ACROSS THE NORTH HALF OF THE CWA...THE EXTREME WIND CHILLS
WILL CONTINUE OVERNIGHT. SOUTH HALF OF THE CWA EXPECTED TO HAVE
WIND CHILLS OF 15 TO 25 BELOW CONTINUING.

WARM AIR ADVECTION FINALLY BEGINS TO SET UP FRIDAY AFTERNOON AS
THE HIGH SINKS FURTHER TOWARD THE SOUTHEAST. DECENT DIURNAL SWING
IN TEMPERATURES EXPECTED AS HIGHS REACH INTO THE TEENS FRIDAY
AFTERNOON. NOT MUCH DECLINE IS EXPECTED FRIDAY NIGHT AS BRISK
SOUTHERLY FLOW CONTINUES.

NEXT CLIPPER SYSTEM WILL DIVE SOUTHEAST INTO THE WESTERN GREAT
LAKES REGION BY SATURDAY MORNING. NAM-WRF THE ODD MODEL OUT IN
TRACKING THE SYSTEM MUCH FURTHER WEST ACROSS THE DAKOTAS INTO
WESTERN IOWA...SO ITS SOLUTION WAS DISCOUNTED. THE ECMWF/GFS AND
CANADIAN MODELS MORE UNIFORM IN THE TRACK OF THIS SYSTEM WITH LOW
PRESSURE MOVING FROM NEAR MINNEAPOLIS TO DETROIT...WITH ITS
TRAILING COLD FRONT SWEEPING ACROSS ILLINOIS. MOISTURE IS RATHER
MEAGER WITH THIS SYSTEM AND IS CURRENTLY EXPECTED TO BE LIMITED
TO AREAS CLOSER TO THE LOW TRACK. KEPT LOW CHANCE POPS GOING
ACROSS THE NORTHERN EDGE OF THE FORECAST AREA...PRIMARILY LATE
FRIDAY NIGHT INTO SATURDAY MORNING. TEMPERATURES EXPECTED TO MAKE
A DECENT RECOVERY DESPITE THE PASSAGE OF THE BOUNDARY...ALTHOUGH
STILL REMAINING A BIT BELOW NORMAL FOR MID JANUARY.

LONG TERM...SUNDAY THROUGH WEDNESDAY...

NO CHANGES WERE MADE TO THIS PART OF THE FORECAST. PERSISTENT
UPPER PATTERN OF RIDGE WEST/TROUGH EAST EXPECTED TO CONTINUE
ACROSS THE NATION INTO EARLY NEXT WEEK...AS THE RIDGE SLOWLY
BEGINS TO BREAK DOWN. MORE MODERATION IN TEMPERATURES IS EXPECTED
AS FLOW TRIES TO BECOME MORE ZONAL.


&&

.AVIATION...
ISSUED 535 AM CST THU JAN 15 2009

ARCTIC HIGH PRESSURE WILL SETTLE SOUTHEAST ACROSS THE MIDWEST
TODAY WHICH WILL CONTINUE TO BRING VFR CONDITIONS TO THE AREA
THRU THE PERIOD. FORECAST SOUNDINGS SHOWING THE PSBLTY OF
THE DVLPMT OF FEW-SCT STRATOCU ARND 1500 FEET LATER THIS MRNG.
SFC WNDS WL REMAIN OUT OF THE NORTHWEST TODAY WITH FORECAST
SOUNDINGS AND UPSTREAM PROFILERS/ACARS SUGGESTING THE PSBLTY
OF A FEW GUSTS ARND 20 KTS LATER THIS MRNG INTO THE AFTN HOURS.
WINDS SHOULD DROP OFF TO 5 KTS OR LESS THIS EVENING.

SMITH
&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 12 PM CST FRIDAY FOR ILZ049>057-
061>063-066>068-071>073.

WIND CHILL WARNING UNTIL 12 PM CST FRIDAY FOR ILZ027>031-036>038-
040>048.

&&

$$

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000
FXUS63 KLOT 151139
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
539 AM CST THU JAN 15 2009

.DISCUSSION...
340 AM CST

EXTREME WIND CHILLS THROUGH FRIDAY MORNING ALONG WITH POTENTIAL FOR
MORE SNOW ACCUMULATION FRIDAY NIGHT/SATURDAY MORNING WILL CONTINUE
TO BE THE MAIN FORECAST ISSUES. A WIND CHILL WARNING REMAINS IN
EFFECT FOR ALL OF NORTHERN ILLINOIS AND NORTHWEST INDIANA THROUGH
FRIDAY MORNING.

LAKE EFFECT SNOW HAS ENDED ACROSS PORTER COUNTY...ALTHOUGH LAKE
EFFECT CLOUDINESS AND A FEW FLURRIES MAY PERSIST OVER NEXT SEVERAL
HOURS ACROSS FAR NORTHEAST PORTER COUNTY BEFORE CLEARING. ACROSS THE
REMAINDER OF THE FORECAST AREA...CLEAR SKIES AND CONTINUED ADVECTION
OF ARCTIC AIR MASS INTO THE REGION IS THE MAIN STORY. WIND CHILLS
ACROSS MOST OF THE AREA ALREADY RUNNING IN THE 20 BELOW TO 35 BELOW
RANGE AT 08Z. SFC PARCEL TRAJECTORIES WOULD SUPPORT SOURCE REGION OF
AIR MASS FROM CENTRAL MINNESOTA WHERE HIGHS YESTERDAY RANGED 5 BELOW
TO 15 BELOW. SOME SLIGHT MODIFICATION OF THE AIR MASS IS POSSIBLE
TODAY INTO TONIGHT...SO STILL FEEL THAT HIGHS AROUND 5 BELOW ARE IN
THE BALLPARK FOR TODAY...WITH A FEW DEGREES WARMER FOR CHICAGO METRO
AREA. TRACK OF THE SFC HIGH ACROSS THE MID MS RIVER VALLEY
TODAY/TONIGHT WILL MAINTAIN A WEST NORTHWEST WIND TODAY OF 10 TO 15
MPH WITH GUSTS UP TO AROUND 20 MPH TODAY. WITH THE POSSIBILITY OF
MORE GUSTINESS TODAY...THE EARLY MORNING WIND CHILLS OF 20 BELOW TO
35 BELOW WILL NOT IMPROVE SIGNIFICANTLY THROUGH THE DAY LIKELY
REMAINING IN THE 20 BELOW TO 30 BELOW RANGE THIS AFTERNOON. TONIGHT
STILL SHAPING UP TO BE THE COLDEST NIGHT OF THE FORECAST PERIOD WITH
A BETTER CHANCE OF A STRONGER LOW LEVEL INVERSION DEVELOPING. HAVE
NOT MADE MANY CHANGES TO GOING FORECAST OF LOWS 15 BELOW TO 20 BELOW
TONIGHT...AND PERHAPS EVEN SLIGHTLY COLDER FAR NORTH. THE RECORD LOW
MIN FOR BOTH ORD AND RFD FOR JAN 16TH IS 25 BELOW SET IN 1982. A
SLIGHTLY TIGHTER SFC PRESSURE GRADIENT NORTH OF THE SFC HIGH MAY
PREVENT RFD FROM QUITE REACHING THIS RECORD...BUT IT COULD BE CLOSE.
WIND CHILLS TONIGHT ACROSS ENTIRE CWA ARE EXPECTED BACK IN THE 30
BELOW TO 40 BELOW RANGE. NO CHANGES ANTICIPATED TO THE WIND CHILL
WARNING THAT IS IN EFFECT FOR ALL OF THE FORECAST AREA FROM THIS
MORNING THROUGH FRIDAY MORNING.

CORE OF COLDEST LOW LEVEL AIR BEGINS TO SLIDE OFF TO THE EAST FRIDAY
MORNING...ALTHOUGH WEAK SFC RIDGE AXIS WILL LINGER BACK INTO
NORTHERN ILLINOIS RESULTING IN WEAK LOW LEVEL THERMAL ADVECTION AND
LITTLE POTENTIAL FOR DRAMATIC TEMPERATURE RECOVERY WITH TEMPS NOT
RISING MUCH MORE THAN 0 TO 5 ABOVE FOR THE AFTERNOON. DEPARTING
RIDGE AND DEVELOPMENT OF SOUTHERLY FLOW AHEAD OF NEXT CLIPPER SYSTEM
SHOULD SUPPORT RISING TEMPERATURES FRIDAY NIGHT. THE NAM IS A SLOW
OUTLIER IN COMPARISON WITH GFS/GFS ENSEMBLES/UKMET/ECMWF/SREF IN TERMS
OF TIMING WITH THIS CLIPPER AND HAVE PUT MORE EMPHASIS ON HPC
PREFERRED ECMWF/GFS FOR THE HANDLING OF THIS SYSTEM. GFS ISENTROPIC
PROGS OF 285K SFC STILL SUGGEST FAR NORTH CENTRAL/NORTHEAST ILLINOIS
EXTENDING SOUTHEASTWARD INTO NORTHERN INDIANA INLINE FOR DEEPER
SATURATION AND SNOW POTENTIAL. STILL EARLY...BUT DEPENDING ON EXACT
TRACK...FAR NORTHERN ILLINOIS INTO NORTHWEST INDIANA COULD RECEIVE 1
TO 3 INCHES WITH PERHAPS SOME SLIGHTLY HIGHER AMOUNTS. AT THIS TIME
IT APPEARS MOST OF ACCUMULATING SNOW WOULD OCCUR OVERNIGHT FRIDAY
INTO SATURDAY MORNING. SERIES OF WAVES WILL MOVE INTO WESTERN GREAT
LAKES SATURDAY/SUNDAY KEEPING NORTHERN ILLINOIS/NORTHWEST INDIANA IN
CYCLONIC FLOW WITH A POTENTIAL FOR SCATTERED FLURRIES OR SNOW
SHOWERS. SATURDAY NIGHT INTO EARLY SUNDAY MAY ALSO FEATURE SOME LAKE
EFFECT SNOW SHOWERS FOR NORTHEAST INDIANA BUT MAGNITUDE OF COLD AIR
MUCH LESS IMPRESSIVE BY THIS TIME WITH LOW INVERSION HEIGHTS. CHANCE
OF SNOW SHOWERS LINGERS INTO MONDAY...BUT BY MONDAY NIGHT AND
TUESDAY...MEDIUM RANGE MODELS HAVE BEEN CONSISTENT IN MORE
PROGRESSION WITH WESTERN CONUS RIDGE AXIS BEGINNING TO BUILD INTO THE
CENTRAL PART OF THE COUNTRY. THIS SHOULD ALLOW FOR DRY CONDITIONS
TUESDAY/WEDNESDAY WITH MORE MANAGEABLE HIGHS IN THE UPPER 20S TO MID
30S TUES/WED.

MARSILI

.AVIATION...

539 AM CST

1200 UTC TAFS...WINDS ARE MAIN FOCUS OF THIS TERMINAL FORECAST
PERIOD...AS STRONG ARCTIC HIGH BUILDS SOUTHEAST ACROSS THE PLAINS
NEXT 24-36 HOURS.

STRONG INVERSION HAS ALLOWED WINDS TO DECOUPLE EARLY THIS MORNING
WITH SPEEDS GENERALLY 10 KNOTS OR LESS AND WEST/NORTHWESTERLY
DIRECTION FROM 290-320 DEGREES. SUSPECT WE WONT MIX VERY DEEPLY
TODAY THOUGH ACARS SOUNDINGS OUT OF KRFD THIS MORNING INDICATE 20
KNOTS SEVERAL HUNDRED FEET AGL. GIVEN POSITION OF FORECAST AREA IN
TIGHTER SURFACE PRESSURE GRADIENT BETWEEN WEAK TROUGH OVER
NORTHERN LAKES AND MASSIVE HIGH TO OUR WEST EXPECT THAT SHALLOW
MIXING WILL RESULT IN A SLIGHT DIURNAL INCREASE IN WINDS/GUSTS TO
20 KNOT RANGE. EXPECT WILL SEE SIMILAR DECOUPLING TONIGHT WITH
WINDS FALLING UNDER 10 KNOTS.

NOT MUCH IN THE WAY OF CLOUDS IN DRY POLAR AIRMASS. SOME CIRRUS
WELL TO THE NORTH TODAY WITH A SHORT WAVE TROUGH MOVING THROUGH
UPPER LAKES/ONTARIO...AND JET INDUCED CIRRUS WELL OF TO OUR SOUTH.

RATZER

.MARINE...
340 AM CST

BRISK NORTHWEST/WINDS WINDS TO CONTINUE ACROSS LAKE MICHIGAN
TODAY...AS LAKE REMAINS IN MODERATE GRADIENT REGION BETWEEN STRONG
ARCTIC HIGH PRESSURE DROPPING ACROSS THE PLAINS...AND WEAK LOW
PRESSURE TROUGHING LINGERING ACROSS NORTHERN LAKES/EASTERN ONTARIO.
FORECAST SOUNDINGS OVER LAKE SUPPORT WINDS HANGING IN 20-25 KNOT
RANGE FOR THE MOST PART...WITH DIRECTION BETWEEN 280-310 DEGREES
INTO FRIDAY BEFORE NORTHERN EXTENT OF SURFACE HIGH PRESSURE RIDGE
ARRIVES. WITH AIR TEMPS IN THE SINGLE DIGITS BELOW/ABOVE ZERO FROM
WEST TO EAST...20 KNOT WINDS EXPECTED TO PRODUCE HEAVY FREEZING
SPRAY IN AREAS OF ICE FREE OPEN WATER. THIS THREAT SHOULD GRADUALLY
SUBSIDE FRIDAY AS WINDS DIMINISH A BIT...BACK TO THE SOUTH/SOUTHWEST
AND ALLOW TEMPS TO MODERATE A BIT ACROSS THE LAKE.

ANOTHER LOW PRESSURE AREA TO AFFECT THE WESTERN LAKES FRIDAY NIGHT
INTO SATURDAY. WRF MODEL APPEARS TO BE AN OUTLIER WITH SURFACE LOW
PASSING TO THE SOUTH OF THE LAKE SATURDAY AFTERNOON/EVENING...WHILE
OTHER GUIDANCE APPEARS TO BE IN AGREEMENT IN PASSING LOW OVER LAKE
AND INTO SOUTHERN LOWER MICHIGAN. HAVE USED THE GFS/ECMWF/UKMET/GEM
CONSENSUS IN TWEAKING WIND GRIDS/FORECAST FOR LOW PASSAGE. SOUTH
WINDS EXPECTED TO INCREASE FRIDAY NIGHT AHEAD OF LOW...WITH A BRIEF
PERIOD OF MODERATE NORTHERLY FLOW IN ITS WAKE SUNDAY.

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WIND CHILL WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
ILZ023-ILZ032-ILZ033-ILZ039 UNTIL NOON FRIDAY.

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL
NOON FRIDAY.

LM...HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878
UNTIL 6 AM SATURDAY.

HEAVY FREEZING SPRAY WARNING...LMZ740-LMZ741-LMZ742-LMZ743-
LMZ744 UNTIL 10 AM THURSDAY.

SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO BURNS HARBOR UNTIL
10 AM THURSDAY.

HEAVY FREEZING SPRAY WARNING...NEARSHORE BURNS HARBOR TO MICHIGAN CITY IN UNTIL NOON THURSDAY.

SMALL CRAFT ADVISORY...NEARSHORE BURNS HARBOR TO MICHIGAN CITY IN UNTIL 9 PM THURSDAY.

000
FXUS63 KLOT 150945
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
345 AM CST THU JAN 15 2009

.DISCUSSION...
340 AM CST

MARSILI

.AVIATION...
1033 PM CST

06Z TAFORS...RIDGE OF HI PRES EXTENDS FM SASK ACROSS THE
DAKOTAS...MID MO AND MD MS VALLEYS LATE THIS EVE. SOUTHERN EXTENT
OF RIDGE TO SHIFT EASTWARD ACROSS THE OH AND TN VALLEYS DURING THU
AFTERNOON AND EVE MAINTAINING NW SFC WIND. FAIRLY STRONG PRES
GRADIENT ACROSS THE LOCAL TERMINALS THOUGH IS SFC PARTIALLY
DECOUPLED DUE TO VERY COLD DRY AIR...FRESH SNOW COVER AND CLEAR
SKY. WIND EXPECTED TO PICK UP A BIT DIURNALLY THU MORN.

ANOTHER SHORT WAVE CURRENTLY DROPPING SSE FM MANITOBA INTO FAR
WESTERN ONT WITH PATCHY MID CLOUDS. DISTURBANCE TO TURN MORE
SOUTHEASTWARD AS IT DROPS FURTHER INTO THE UPPER TROF AND WHILE
MAY BE A FEW CLOUDS SEEN OVR NORTHERN IL MAIN AREA OF MID
CLOUDINESS EXPECTED TO MOVE INTO THE CENTRAL GRTLKS DURING THE
DAY THU.

TRS

.MARINE...
340 AM CST

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL
NOON FRIDAY.

LM...HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878
UNTIL 6 AM SATURDAY.

HEAVY FREEZING SPRAY WARNING...LMZ740-LMZ741-LMZ742-LMZ743-
LMZ744 UNTIL 10 AM THURSDAY.

SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO BURNS HARBOR UNTIL
10 AM THURSDAY.

HEAVY FREEZING SPRAY WARNING...NEARSHORE BURNS HARBOR TO MICHIGAN CITY IN UNTIL NOON THURSDAY.

SMALL CRAFT ADVISORY...NEARSHORE BURNS HARBOR TO MICHIGAN CITY IN UNTIL 9 PM THURSDAY.


000
FXUS63 KILX 150811
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
211 AM CST THU JAN 15 2009

.DISCUSSION...
ISSUED 205 AM CST THU JAN 15 2009

ARCTIC AIRMASS AGGRESSIVELY SPREADING ACROSS CENTRAL AND SOUTHEAST
ILLINOIS OVERNIGHT. UPSTREAM WIND CHILLS WERE IN THE 40S BELOW
ACROSS MANY PARTS OF IOWA...WITH AIR TEMPERATURES CLOSE TO 20
BELOW. TEMPERATURES IN THE NORTHWEST CWA HAD ALREADY PLUNGED TO
NEAR 15 BELOW BY 2 AM...WITH THE ZERO DEGREE LINE AS FAR SOUTH AS
I-70. WIND CHILLS BELOW THE -25F WARNING CRITERIA WERE IN MANY
AREAS NORTH OF A MACOMB TO BLOOMINGTON LINE...AND WERE IN THE
TEENS TO LOWER 20S BELOW ACROSS THE REMAINDER OF CENTRAL ILLINOIS.

TEMPERATURES AND WIND CHILLS THROUGH TOMORROW MORNING ARE THE PRIMARY
CONCERN WITH THIS FORECAST PACKAGE...FOLLOWED BY POTENTIAL EFFECTS
OF CLIPPER SYSTEM OVER THE WEEKEND.

SHORT TERM...TODAY THROUGH SATURDAY...

CENTER OF ARCTIC HIGH WAS OVER THE DAKOTAS EARLY THIS MORNING...AND
THIS IS EXPECTED TO SINK SOUTHEAST INTO MISSOURI TONIGHT. ENOUGH
OF A PRESSURE GRADIENT WILL REMAIN IN PLACE TO KEEP WINDS IN THE
10-15 MPH RANGE. TEMPERATURES EXPECTED TO CONTINUE FALLING FOR A
FEW HOURS AFTER SUNRISE BEFORE ATTEMPTING A COMEBACK...BUT MOST
LOCATIONS NORTH OF I-72 WILL REMAIN BELOW ZERO TODAY. MORNING WIND
CHILLS OF 30-40 BELOW ACROSS THE NORTH WILL ONLY SLIGHTLY RISE
THIS AFTERNOON. NORTHERN HALF OF THE EXISTING WIND CHILL ADVISORY
AREA...GENERALLY BETWEEN I-72 AND I-70...WILL LIKELY SEE WIND
CHILLS BELOW -25F FOR A COUPLE HOURS THIS MORNING...BUT WILL NOT
EXPAND THE WIND CHILL WARNING SOUTHWARD DUE TO THE SHORT DURATION
OF THIS THRESHOLD VALUE.

WINDS EXPECTED TO TAPER OFF OVERNIGHT AS THE HIGH MOVES INTO THE
OHIO VALLEY. HOWEVER...WITH AIR TEMPERATURES OF 10 TO 20 BELOW
ZERO ACROSS THE NORTH HALF OF THE CWA...THE EXTREME WIND CHILLS
WILL CONTINUE OVERNIGHT. SOUTH HALF OF THE CWA EXPECTED TO HAVE
WIND CHILLS OF 15 TO 25 BELOW CONTINUING.

WARM AIR ADVECTION FINALLY BEGINS TO SET UP FRIDAY AFTERNOON AS
THE HIGH SINKS FURTHER TOWARD THE SOUTHEAST. DECENT DIURNAL SWING
IN TEMPERATURES EXPECTED AS HIGHS REACH INTO THE TEENS FRIDAY
AFTERNOON. NOT MUCH DECLINE IS EXPECTED FRIDAY NIGHT AS BRISK
SOUTHERLY FLOW CONTINUES.

NEXT CLIPPER SYSTEM WILL DIVE SOUTHEAST INTO THE WESTERN GREAT
LAKES REGION BY SATURDAY MORNING. NAM-WRF THE ODD MODEL OUT IN
TRACKING THE SYSTEM MUCH FURTHER WEST ACROSS THE DAKOTAS INTO
WESTERN IOWA...SO ITS SOLUTION WAS DISCOUNTED. THE ECMWF/GFS AND
CANADIAN MODELS MORE UNIFORM IN THE TRACK OF THIS SYSTEM WITH LOW
PRESSURE MOVING FROM NEAR MINNEAPOLIS TO DETROIT...WITH ITS
TRAILING COLD FRONT SWEEPING ACROSS ILLINOIS. MOISTURE IS RATHER
MEAGER WITH THIS SYSTEM AND IS CURRENTLY EXPECTED TO BE LIMITED
TO AREAS CLOSER TO THE LOW TRACK. KEPT LOW CHANCE POPS GOING
ACROSS THE NORTHERN EDGE OF THE FORECAST AREA...PRIMARILY LATE
FRIDAY NIGHT INTO SATURDAY MORNING. TEMPERATURES EXPECTED TO MAKE
A DECENT RECOVERY DESPITE THE PASSAGE OF THE BOUNDARY...ALTHOUGH
STILL REMAINING A BIT BELOW NORMAL FOR MID JANUARY.


LONG TERM...SUNDAY THROUGH WEDNESDAY...

NO CHANGES WERE MADE TO THIS PART OF THE FORECAST. PERSISTENT
UPPER PATTERN OF RIDGE WEST/TROUGH EAST EXPECTED TO CONTINUE
ACROSS THE NATION INTO EARLY NEXT WEEK...AS THE RIDGE SLOWLY
BEGINS TO BREAK DOWN. MORE MODERATION IN TEMPERATURES IS EXPECTED
AS FLOW TRIES TO BECOME MORE ZONAL.

GEELHART
&&

.AVIATION...
ISSUED 1110 PM CST WED JAN 14 2009...FOR THE 06Z TAFS

THE BULK OF THE LOW LEVEL CLOUDS HAVE MOVED EAST OF IL.
HOWEVER...PATCHES OF LOW CLOUDS ARE STILL PRESENT ACROSS OUR CWA
AS THE SURFACE RIDGE BUILDS EASTWARD INTO IL. IT IS DIFFICULT TO
DISCERN THE LOCATION OF THE PATCHY LOW CLOUDS ON THE SATELLITE
FOG PRODUCT. A BROKEN MVFR CIG CAN NOT BE RULED OUT FOR SHORT
PERIODS TONIGHT. WILL GO WITH SCT 1500 TO 2000 FT CLOUDS AT ALL
SITES TO COVER AND CIGS THAT DEVELOP. A FEW FLURRIES MAY FALL FROM
THOSE CLOUDS...BUT NOT ENOUGH TO WARRANT A MENTION IN THE TAFS.

WINDS HAVE DECREASED UNDER THE ADVANCING RIDGE...BUT SUSTAINED 10
TO 15 KTS STILL LIKELY THE REST OF THE NIGHT BASED ON THE PRESSURE
GRADIENT OBSERVED IN THE LATEST MSLP ANALYSIS.

PREVAILING WINDS WILL REMAIN NW THROUGHOUT THE TAF PERIOD.

SHIMON
&&

.CLIMATE...
ISSUED 205 AM CST THU JAN 15 2009

ONLY A FEW SPOTS IN THE NORTHERN CWA ARE EXPECTED TO THREATEN
ANY RECORD LOWS AT THIS TIME. RECORDS ARE AS FOLLOWS...

LOCATION               THURSDAY           FRIDAY
DECATUR              -22 IN 1927       -21 IN 1977
GALESBURG            -21 IN 1994       -20 IN 1977
LINCOLN              -34 IN 1977       -19 IN 1977
NORMAL               -21 IN 1979       -20 IN 1977
PEORIA               -22 IN 1979       -20 IN 1977
SPRINGFIELD          -17 IN 1888       -20 IN 1977
URBANA               -18 IN 1893       -17 IN 1977

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 12 PM CST FRIDAY FOR ILZ049>057-
061>063-066>068-071>073.

WIND CHILL WARNING UNTIL 12 PM CST FRIDAY FOR ILZ027>031-036>038-
040>048.

&&

$$


000
FXUS63 KILX 150511
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1111 PM CST WED JAN 14 2009

.DISCUSSION...
ISSUED 847 PM CST WED JAN 14 2009

THE CLIPPER IS RAPIDLY PULLING AWAY FROM ILLINOIS...WITH THE LOW
CENTER NOW NEARING WEST VIRGINIA. LINGERING LOW CLOUDS AND
FLURRIES ARE MAINLY CONFINED TO AREAS EAST OF A LINE FROM
CHAMPAIGN TO EFFINGHAM. THE PRESSURE RISES BEHIND THE LOW ARE
CONTINUING TO DECREASE...AND WIND GUSTS PRIMARILY IN THE EASTERN
CWA.

THE PRESSURE GRADIENT WILL REMAIN TIGHT ENOUGH FOR SUSTAINED WINDS
OF 10 TO 15 MPH. TEMPS ARE FALLING OFF STEADILY THIS
EVENING...AND THEY APPEAR ON TRACK TO REACH THE TEENS BELOW ZERO
IN OUR N CWA...MAINLY N OF PIA TO BMI. IT WILL NOT TAKE MUCH WIND
TO PUSH WIND CHILL READINGS DOWN TO WARNING LEVELS OF -25F OR
COLDER IN THE N HALF OF THE CWA.

THE LATEST GUIDANCE CONTINUES TO SHOW BITTERLY COLD WIND CHILLS
WILL CONTINUE THROUGH FRIDAY MORNING...DESPITE LIGHTER WINDS BY
TOMORROW NIGHT. AIR TEMPS WILL BE ABOUT 5 DEG COLDER THURSDAY
NIGHT...SO ANY WIND AT ALL WILL PRODUCE THE NECESSARY WIND CHILLS
FOR THE CURRENT HEADLINES.

THE ONLY ADJUSTMENTS TO THE GRIDS WERE TO REMOVE BLOWING SNOW IN
THE WESTERN CWA...AND TO UPDATE THE WINDS AND WIND GUSTS TO
REFLECT THE CURRENT TRENDS.

UPDATED ZONES AND GRIDS ARE ALREADY AVAILABLE.

SHIMON

&&

.AVIATION...
ISSUED 1110 PM CST WED JAN 14 2009...FOR THE 06Z TAFS

THE BULK OF THE LOW LEVEL CLOUDS HAVE MOVED EAST OF IL.
HOWEVER...PATCHES OF LOW CLOUDS ARE STILL PRESENT ACROSS OUR CWA
AS THE SURFACE RIDGE BUILDS EASTWARD INTO IL. IT IS DIFFICULT TO
DISCERN THE LOCATION OF THE PATCHY LOW CLOUDS ON THE SATELLITE
FOG PRODUCT. A BROKEN MVFR CIG CAN NOT BE RULED OUT FOR SHORT
PERIODS TONIGHT. WILL GO WITH SCT 1500 TO 2000 FT CLOUDS AT ALL
SITES TO COVER AND CIGS THAT DEVELOP. A FEW FLURRIES MAY FALL FROM
THOSE CLOUDS...BUT NOT ENOUGH TO WARRANT A MENTION IN THE TAFS.

WINDS HAVE DECREASED UNDER THE ADVANCING RIDGE...BUT SUSTAINED 10
TO 15 KTS STILL LIKELY THE REST OF THE NIGHT BASED ON THE PRESSURE
GRADIENT OBSERVED IN THE LATEST MSLP ANALYSIS.

PREVAILING WINDS WILL REMAIN NW THROUGHOUT THE TAF PERIOD.

SHIMON
&&

.CLIMATE...
ISSUED 1101 PM CST WED JAN 14 2009

ALTHOUGH THE ARCTIC AIRMASS COMING INTO THE MIDWEST WILL BE THE
COLDEST OF THE SEASON SO FAR...IT DOES NOT APPEAR THAT ANY RECORD
LOWS WILL BE THREATENED. HERE ARE THE STANDING RECORD LOW
TEMPERATURES FOR A FEW LOCATIONS OVER THE FORECAST AREA...

CITY...RECORD LOW TONIGHT...RECORD LOW THURSDAY NIGHT

PEORIA...-22 IN 1979...-20 IN 1977
SPRINGFIELD...-17 IN 1888...-20 IN 1977
LINCOLN...-34 IN 1977...-19 IN 1977
URBANA...-18 IN 1893...-17 IN 1977
GALESBURG...-21 IN 1994...-20 IN 1977

THE RECORD LOW OF -34 FOR LINCOLN TONIGHT IS ALSO THE ALL-TIME
RECORD LOW TEMPERATURE FOR LINCOLN.

&&

.PREV DISCUSSION...
ISSUED 300 PM CST WED JAN 14 2009

SHORT TERM...TONIGHT THROUGH SATURDAY...
SURFACE LOW MOVED RAPIDLY THROUGH CENTRAL ILLINOIS TODAY AND IS
ALREADY INTO EASTERN INDIANA. MOST OF THE ACCUMULATING SNOW HAS
ENDED OVER THE AREA...BUT STRONG WINDS ALONG WITH THE POWDERY SNOW
WILL MAKE FOR REDUCED VISIBILITIES AND DIFFICULT TRAVEL AT LEAST
THROUGH THE AFTERNOON COMMUTE. WILL THEREFORE KEEP THE WINTER
WEATHER ADVISORY FOR BLOWING SNOW GOING UNTIL 6 PM...AND IT CAN BE
EXTENDED IF POOR VISIBILITIES CONTINUE ANY LONGER.

LARGE 1046 MB SURFACE HIGH IS CENTERED JUST NORTH OF NORTH DAKOTA
AND IT WILL DIVE SOUTHEASTWARD TO WESTERN IOWA BY THIS TIME ON
THURSDAY. BITTERLY COLD AIR WILL BECOME ENTRENCHED OVER THE MIDWEST
AND WILL BE SLOW TO ERODE AWAY. TEMPERATURES BY DAWN TONIGHT WILL
LIKELY REACH -15 OVER THE FAR NORTH...AND 0-5 ABOVE IN THE
SOUTHEAST. EVEN COLDER TEMPERATURES ARE EXPECTED FRIDAY MORNING AS
THE CENTER OF THE RIDGE MOVES OVER THE AREA AND RADIATIONAL COOLING
TAKES PLACE OVER A FRESH SNOW FIELD. AIR TEMPERATURES AROUND 12Z
FRIDAY SHOULD RANGE FROM -18 OVER THE FAR NORTH TO -5 IN THE
SOUTHEAST. WILL KEEP THE WIND CHILL HEADLINES AS THEY ARE WITH
VALUES FROM -25 TO -35 COMMON IN THE WARNING AREA. AREAS WITHIN THE
ADVISORY WILL SEE -15 TO -25.

AS THE SURFACE HIGH MOVES EAST LATER FRIDAY...WARM ADVECTION WILL
SET UP AHEAD OF THE NEXT ALBERTA CLIPPER THAT IS EXPECTED TO TRACK
FROM MINNESOTA FRIDAY NIGHT ACROSS FAR NORTHERN ILLINOIS ON
SATURDAY. QPF SHOULD NOT BE HIGH DUE TO THE COMPLETE LACK OF
MOISTURE...BUT A FEW TENTHS INCH OF SNOW COULD BE SHAKEN OUT OVER
THE NORTH. WILL HAVE SOME LOW-END CHANCE POPS IN THE NORTH FOR
FRIDAY NIGHT & SATURDAY...THEN SLIGHT CHANCE IN THE EAST SATURDAY
NIGHT.

LONG TERM...SUNDAY THROUGH WEDNESDAY...
THE OVERALL UPPER PATTERN FEATURING A LONG-WAVE TROUGH OVER THE
EASTERN CONUS WILL CONTINUE INTO EARLY NEXT WEEK. BY TUESDAY AND
WEDNESDAY...THIS TROUGH WILL BE MOVING EAST AND WILL ALLOW HIGHER
HEIGHTS AND WARMER TEMPERATURES TO RETURN TO THE REGION. BEFORE THE
TROUGH MOVES OUT THOUGH...MODELS HAVE BEEN HINTING AS ONE LAST
CLIPPER TO COME SOUTHEASTWARD TOWARD ILLINOIS IN THE GENERAL SUNDAY
NIGHT/MONDAY TIME FRAME. WILL HAVE SOME SLIGHT CHANCE POPS IN THE
NORTH SUNDAY NIGHT FOR LIGHT SNOW IN THE WARM ADVECTION PATTERN
AHEAD OF THE SURFACE LOW...THEN DRY AFTERWORDS. TEMPERATURES WILL BE
ON A WARMING TREND...WITH 25-30 DEGREES ON SUNDAY RISING TO 35-40 BY
NEXT WEDNESDAY.

04


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 12 PM CST FRIDAY FOR ILZ049>057-
061>063-066>068-071>073.

WIND CHILL WARNING UNTIL 12 PM CST FRIDAY FOR ILZ027>031-036>038-
040>048.

&&

$$

000
FXUS63 KLOT 150442
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1042 PM CST WED JAN 14 2009

.DISCUSSION...
656 PM CST

WINDS ARE BEGINNING TO DIMINISH OVER OUR NORTHWESTERN COUNTIES AS
STRONGEST PRESSURE RISES CONTINUE TO MAKE THEIR WAY SOUTHEASTWARD.
WITH WINDS AT MOST LOCATIONS NOW DOWN TO 10KT OR LESS WILL BEGIN
TO TRIM SOME OF THE COUNTIES OFF THE WINTER WEATHER ADVISORY.

ALSO...INTENSE LAKE EFFECT SNOW PLUME CONTINUES TO MIGRATE SLOWLY
EASTWARD AS INDIVIDUAL ELEMENTS WITHIN THE BAND MOVE SOUTHWARD.
HAVE RECEIVED NUMEROUS REPORTS OF ZERO VISIBILITIES WITH WHITE-OUT
CONDITIONS AND SNOWFALL RATES OF 1-2 INCHES IN AN HOUR OR LESS.
THANKFULLY...MULTIPLE MESOLOWS HAVE BEEN DEVELOPING WITHIN THE
LAKE EFFECT PLUME AND THESE SMALL SCALE CIRCULATIONS HAVE KEPT THE
LINE FAIRLY KINKY AND GENERALLY KEPT DURATION OF THE MOST INTENSE
SNOW FAIRLY SHORT.

PLUME HAS SHIFTED EAST OF LAKE COUNTY AND WILL BE DOWNGRADING THE
WARNING TO A WINTER WX ADVISORY SHORTLY. SUSPECT THAT PRIOR TO 9PM
WILL BE ABLE TO SHAVE ANOTHER BATCH OF COUNTIES OUT OF THE WINTER
WEATHER ADVISORY AS WINDS CONTINUE TO DIMINISH.

IZZI

.AVIATION...
1033 PM CST

TRS

.MARINE...
1040 PM CST

UPDATE...HAVE CANCELED GALE WARNING AS OBSERVATIONS BELOW
THRESHOLD AND NO SUPPORT FOR GALE FORCE WINDS SEEN IN 00Z GRB
RAOB...MKX- LOT- ORD- MDW VAD WINDS...ACARS...OR 00Z NAM AND RUC
MODEL OUTPUT.

212 PM...LOW PRESSURE MOVING EAST ACROSS THE OHIO VALLEY THIS
AFTERNOON WILL MOVE OFF THE ATLANTIC COAST THURSDAY MORNING. LARGE
STRONG ARCTIC HIGH PRESSURE WILL BUILD ACROSS THE PLAINS TONIGHT
THEN SPREAD SOUTHEAST ACROSS THE OHIO AND TENNESSEE VALLEYS
THURSDAY AND THURSDAY NIGHT. A PERIOD OF GALES IS LIKELY ACROSS
THE SOUTHERN HALF OF LAKE MICHIGAN TONIGHT AS THE GRADIENT
TIGHTENS BETWEEN THESE TWO FEATURES. WINDS DIMINISH TO 30 KNOTS BY
MORNING BUT GRADIENT LOOKS LIKE IT WILL MAINTAIN 25-30KTS THRU
FRIDAY MORNING BEFORE IT FINALLY WEAKENS. WINDS THEN QUICKLY TURN
SOUTHERLY FRIDAY NIGHT AS ANOTHER CLIPPER SYSTEM MOVES ACROSS THE
WESTERN LAKES WITH WINDS TURNING BACK NORTHERLY SATURDAY. CMS

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ033-ILZ039 UNTIL MIDNIGHT THURSDAY.

WIND CHILL WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
ILZ023-ILZ032-ILZ033-ILZ039 UNTIL NOON FRIDAY.

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL
NOON FRIDAY.

WINTER STORM WARNING...INZ002 UNTIL MIDNIGHT THURSDAY.

WINTER WEATHER ADVISORY...INZ010-INZ011-INZ019 UNTIL MIDNIGHT
THURSDAY.

LM...HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878
UNTIL 6 AM SATURDAY.

HEAVY FREEZING SPRAY WARNING...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL
10 AM THURSDAY.

SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO BURNS HARBOR UNTIL
3 AM THURSDAY.

HEAVY FREEZING SPRAY WARNING...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL NOON THURSDAY.

SMALL CRAFT ADVISORY...NEARSHORE BURNS HARBOR TO MICHIGAN CITY IN UNTIL 9 PM THURSDAY.

000
FXUS63 KLOT 150437
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1037 PM CST WED JAN 14 2009

.DISCUSSION...
656 PM CST

IZZI

.AVIATION...
1033 PM CST

TRS

.MARINE...

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ033-ILZ039 UNTIL MIDNIGHT THURSDAY.

WIND CHILL WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
ILZ023-ILZ032-ILZ033-ILZ039 UNTIL NOON FRIDAY.

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL
NOON FRIDAY.

WINTER STORM WARNING...INZ002 UNTIL MIDNIGHT THURSDAY.

WINTER WEATHER ADVISORY...INZ010-INZ011-INZ019 UNTIL MIDNIGHT
THURSDAY.

LM...HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878
UNTIL 6 AM SATURDAY.

HEAVY FREEZING SPRAY WARNING...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL
10 AM THURSDAY.

SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO BURNS HARBOR UNTIL
3 AM THURSDAY.

HEAVY FREEZING SPRAY WARNING...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL NOON THURSDAY.

SMALL CRAFT ADVISORY...NEARSHORE BURNS HARBOR TO MICHIGAN CITY IN UNTIL 9 PM THURSDAY.


000
FXUS63 KILX 150315
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
847 PM CST WED JAN 14 2009

.DISCUSSION...
ISSUED 847 PM CST WED JAN 14 2009

THE CLIPPER IS RAPIDLY PULLING AWAY FROM ILLINOIS...WITH THE LOW
CENTER NOW NEARING WEST VIRGINIA. LINGERING LOW CLOUDS AND
FLURRIES ARE MAINLY CONFINED TO AREAS EAST OF A LINE FROM
CHAMPAIGN TO EFFINGHAM. THE PRESSURE RISES BEHIND THE LOW ARE
CONTINUING TO DECREASE...AND WIND GUSTS PRIMARILY IN THE EASTERN
CWA.

THE PRESSURE GRADIENT WILL REMAIN TIGHT ENOUGH FOR SUSTAINED WINDS
OF 10 TO 15 MPH. TEMPS ARE FALLING OFF STEADILY THIS
EVENING...AND THEY APPEAR ON TRACK TO REACH THE TEENS BELOW ZERO
IN OUR N CWA...MAINLY N OF PIA TO BMI. IT WILL NOT TAKE MUCH WIND
TO PUSH WIND CHILL READINGS DOWN TO WARNING LEVELS OF -25F OR
COLDER IN THE N HALF OF THE CWA.

THE LATEST GUIDANCE CONTINUES TO SHOW BITTERLY COLD WIND CHILLS
WILL CONTINUE THROUGH FRIDAY MORNING...DESPITE LIGHTER WINDS BY
TOMORROW NIGHT. AIR TEMPS WILL BE ABOUT 5 DEG COLDER THURSDAY
NIGHT...SO ANY WIND AT ALL WILL PRODUCE THE NECESSARY WIND CHILLS
FOR THE CURRENT HEADLINES.

THE ONLY ADJUSTMENTS TO THE GRIDS WERE TO REMOVE BLOWING SNOW IN
THE WESTERN CWA...AND TO UPDATE THE WINDS AND WIND GUSTS TO
REFLECT THE CURRENT TRENDS.

UPDATED ZONES AND GRIDS ARE ALREADY AVAILABLE.

SHIMON
&&

.AVIATION...
ISSUED 543 PM CST WED JAN 14 2009...FOR THE 00Z TAFS

THE CLIPPER IS PULLING AWAY TO THE EAST. THE LOW CENTER HAS
REACHED SW OHIO. PRESSURE RISES ARE WEAKENING IN OUR WESTERN
CWA...WHICH IS HELPING TO KEEP GUSTS DOWN INTO THE LOWER 20KT RANGE.
BMI/CMI/DEC WILL REMAIN IN THE TIGHTER PRES GRADIENT FOR A FEW
MORE HOURS. STILL...WINDS WILL REMAIN STEADY EVERYWHERE OVERNIGHT
WITH SUSTAINED WINDS IN THE 12 TO 15KT RANGE.

WILL KEEP TEMPO/S FOR MVFR VIS DUE TO BLSN AND ISOLATED SNOW
SHOWERS FOR THE FIRST PART OF THE EVENING AT ALL SITES BUT PIA.
SATELLITE PICS SHOW THE MAJORITY OF CLOUD BANDS AND SNOW SHOWERS
HAVE DISSIPATED...BUT BMI/DEC/CMI MAY SEE THEM THROUGH MID EVENING.

SKIES SHOULD CLEAR OUT AFTER MIDNIGHT...WITH STEADY NW WINDS. A
FEW GUSTS TO 20KT ARE EXPECTED THUR AFTERNOON...SO I ADDED THAT TO
THE 00Z TAFS.

SHIMON
&&

.PREV DISCUSSION...
ISSUED 300 PM CST WED JAN 14 2009

SHORT TERM...TONIGHT THROUGH SATURDAY...
SURFACE LOW MOVED RAPIDLY THROUGH CENTRAL ILLINOIS TODAY AND IS
ALREADY INTO EASTERN INDIANA. MOST OF THE ACCUMULATING SNOW HAS
ENDED OVER THE AREA...BUT STRONG WINDS ALONG WITH THE POWDERY SNOW
WILL MAKE FOR REDUCED VISIBILITIES AND DIFFICULT TRAVEL AT LEAST
THROUGH THE AFTERNOON COMMUTE. WILL THEREFORE KEEP THE WINTER
WEATHER ADVISORY FOR BLOWING SNOW GOING UNTIL 6 PM...AND IT CAN BE
EXTENDED IF POOR VISIBILITIES CONTINUE ANY LONGER.

LARGE 1046 MB SURFACE HIGH IS CENTERED JUST NORTH OF NORTH DAKOTA
AND IT WILL DIVE SOUTHEASTWARD TO WESTERN IOWA BY THIS TIME ON
THURSDAY. BITTERLY COLD AIR WILL BECOME ENTRENCHED OVER THE MIDWEST
AND WILL BE SLOW TO ERODE AWAY. TEMPERATURES BY DAWN TONIGHT WILL
LIKELY REACH -15 OVER THE FAR NORTH...AND 0-5 ABOVE IN THE
SOUTHEAST. EVEN COLDER TEMPERATURES ARE EXPECTED FRIDAY MORNING AS
THE CENTER OF THE RIDGE MOVES OVER THE AREA AND RADIATIONAL COOLING
TAKES PLACE OVER A FRESH SNOW FIELD. AIR TEMPERATURES AROUND 12Z
FRIDAY SHOULD RANGE FROM -18 OVER THE FAR NORTH TO -5 IN THE
SOUTHEAST. WILL KEEP THE WIND CHILL HEADLINES AS THEY ARE WITH
VALUES FROM -25 TO -35 COMMON IN THE WARNING AREA. AREAS WITHIN THE
ADVISORY WILL SEE -15 TO -25.

AS THE SURFACE HIGH MOVES EAST LATER FRIDAY...WARM ADVECTION WILL
SET UP AHEAD OF THE NEXT ALBERTA CLIPPER THAT IS EXPECTED TO TRACK
FROM MINNESOTA FRIDAY NIGHT ACROSS FAR NORTHERN ILLINOIS ON
SATURDAY. QPF SHOULD NOT BE HIGH DUE TO THE COMPLETE LACK OF
MOISTURE...BUT A FEW TENTHS INCH OF SNOW COULD BE SHAKEN OUT OVER
THE NORTH. WILL HAVE SOME LOW-END CHANCE POPS IN THE NORTH FOR
FRIDAY NIGHT & SATURDAY...THEN SLIGHT CHANCE IN THE EAST SATURDAY
NIGHT.

LONG TERM...SUNDAY THROUGH WEDNESDAY...
THE OVERALL UPPER PATTERN FEATURING A LONG-WAVE TROUGH OVER THE
EASTERN CONUS WILL CONTINUE INTO EARLY NEXT WEEK. BY TUESDAY AND
WEDNESDAY...THIS TROUGH WILL BE MOVING EAST AND WILL ALLOW HIGHER
HEIGHTS AND WARMER TEMPERATURES TO RETURN TO THE REGION. BEFORE THE
TROUGH MOVES OUT THOUGH...MODELS HAVE BEEN HINTING AS ONE LAST
CLIPPER TO COME SOUTHEASTWARD TOWARD ILLINOIS IN THE GENERAL SUNDAY
NIGHT/MONDAY TIME FRAME. WILL HAVE SOME SLIGHT CHANCE POPS IN THE
NORTH SUNDAY NIGHT FOR LIGHT SNOW IN THE WARM ADVECTION PATTERN
AHEAD OF THE SURFACE LOW...THEN DRY AFTERWORDS. TEMPERATURES WILL BE
ON A WARMING TREND...WITH 25-30 DEGREES ON SUNDAY RISING TO 35-40 BY
NEXT WEDNESDAY.

04

&&

.CLIMATE...
ISSUED 300 PM CST WED JAN 14 2009

ALTHOUGH THE ARCTIC AIRMASS COMING INTO THE MIDWEST WILL BE THE
COLDEST OF THE SEASON SO FAR...IT DOES NOT APPEAR THAT ANY RECORD
LOWS WILL BE THREATENED. HERE ARE THE STANDING RECORD LOW
TEMPERATURES FOR A FEW LOCATIONS OVER THE FORECAST AREA...

CITY...RECORD LOW TONIGHT...RECORD LOW THURSDAY NIGHT

PEORIA...-22 IN 1979...-20 IN 1977
SPRINGFIELD...-17 IN 1888...-20 IN 1977
LINCOLN...-34 IN 1977...-19 IN 1977
URBANA...-18 IN 1893...-17 IN 1977
GALESBURG...-21 IN 1994...-20 IN 1977

THE RECORD LOW OF -34 FOR LINCOLN TONIGHT IS ALSO THE ALL-TIME
RECORD LOW TEMPERATURE FOR LINCOLN.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 12 PM CST FRIDAY FOR ILZ049>057-
061>063-066>068-071>073.

WIND CHILL WARNING UNTIL 12 PM CST FRIDAY FOR ILZ027>031-036>038-
040>048.

&&

$$


000
FXUS63 KILX 150247
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
847 PM CST WED JAN 14 2009

.DISCUSSION...
ISSUED 847 PM CST WED JAN 14 2009

THE CLIPPER IS RAPIDLY PULLING AWAY FROM ILLINOIS...WITH THE LOW
CENTER NOW NEARING WEST VIRGINIA. LINGERING LOW CLOUDS AND
FLURRIES ARE MAINLY CONFINED TO AREAS EAST OF A LINE FROM
CHAMPAIGN TO EFFINGHAM. THE PRESSURE RISES BEHIND THE LOW ARE
CONTINUING TO DECREASE...AND WIND GUSTS PRIMARILY IN THE EASTERN
CWA.

THE PRESSURE GRADIENT WILL REMAIN TIGHT ENOUGH FOR SUSTAINED WINDS
OF 10 TO 15 MPH. TEMPS ARE FALLING OFF STEADILY THIS
EVENING...AND THEY APPEAR ON TRACK TO REACH THE TEENS BELOW ZERO
IN OUR N CWA...MAINLY N OF PIA TO BMI. IT WILL NOT TAKE MUCH WIND
TO PUSH WIND CHILL READINGS DOWN TO WARNING LEVELS OF -25F OR
COLDER IN THE N HALF OF THE CWA.

THE LATEST GUIDANCE CONTINUES TO SHOW BITTERLY COLD WIND CHILLS
WILL CONTINUE THROUGH FRIDAY MORNING...DESPITE LIGHTER WINDS BY
TOMORROW NIGHT. AIR TEMPS WILL BE ABOUT 5 DEG COLDER THURSDAY
NIGHT...SO ANY WIND AT ALL WILL PRODUCE THE NECESSARY WIND CHILLS
FOR THE CURRENT HEADLINES.

THE ONLY ADJUSTMENTS TO THE GRIDS WERE TO REMOVE BLOWING SNOW IN
THE WESTERN CWA...AND TO UPDATE THE WINDS AND WIND GUSTS TO
REFLECT THE CURRENT TRENDS.

UPDATED ZONES AND GRIDS ARE ALREADY AVAILABLE.

SHIMON
&&

.AVIATION...
ISSUED 543 PM CST WED JAN 14 2009...FOR THE 00Z TAFS

THE CLIPPER IS PULLING AWAY TO THE EAST. THE LOW CENTER HAS
REACHED SW OHIO. PRESSURE RISES ARE WEAKENING IN OUR WESTERN
CWA...WHICH IS HELPING TO KEEP GUSTS DOWN INTO THE LOWER 20KT RANGE.
BMI/CMI/DEC WILL REMAIN IN THE TIGHTER PRES GRADIENT FOR A FEW
MORE HOURS. STILL...WINDS WILL REMAIN STEADY EVERYWHERE OVERNIGHT
WITH SUSTAINED WINDS IN THE 12 TO 15KT RANGE.

WILL KEEP TEMPO/S FOR MVFR VIS DUE TO BLSN AND ISOLATED SNOW
SHOWERS FOR THE FIRST PART OF THE EVENING AT ALL SITES BUT PIA.
SATELLITE PICS SHOW THE MAJORITY OF CLOUD BANDS AND SNOW SHOWERS
HAVE DISSIPATED...BUT BMI/DEC/CMI MAY SEE THEM THROUGH MID EVENING.

SKIES SHOULD CLEAR OUT AFTER MIDNIGHT...WITH STEADY NW WINDS. A
FEW GUSTS TO 20KT ARE EXPECTED THUR AFTERNOON...SO I ADDED THAT TO
THE 00Z TAFS.

SHIMON
&&

.PREV DISCUSSION...
ISSUED 300 PM CST WED JAN 14 2009

SHORT TERM...TONIGHT THROUGH SATURDAY...
SURFACE LOW MOVED RAPIDLY THROUGH CENTRAL ILLINOIS TODAY AND IS
ALREADY INTO EASTERN INDIANA. MOST OF THE ACCUMULATING SNOW HAS
ENDED OVER THE AREA...BUT STRONG WINDS ALONG WITH THE POWDERY SNOW
WILL MAKE FOR REDUCED VISIBILITIES AND DIFFICULT TRAVEL AT LEAST
THROUGH THE AFTERNOON COMMUTE. WILL THEREFORE KEEP THE WINTER
WEATHER ADVISORY FOR BLOWING SNOW GOING UNTIL 6 PM...AND IT CAN BE
EXTENDED IF POOR VISIBILITIES CONTINUE ANY LONGER.

LARGE 1046 MB SURFACE HIGH IS CENTERED JUST NORTH OF NORTH DAKOTA
AND IT WILL DIVE SOUTHEASTWARD TO WESTERN IOWA BY THIS TIME ON
THURSDAY. BITTERLY COLD AIR WILL BECOME ENTRENCHED OVER THE MIDWEST
AND WILL BE SLOW TO ERODE AWAY. TEMPERATURES BY DAWN TONIGHT WILL
LIKELY REACH -15 OVER THE FAR NORTH...AND 0-5 ABOVE IN THE
SOUTHEAST. EVEN COLDER TEMPERATURES ARE EXPECTED FRIDAY MORNING AS
THE CENTER OF THE RIDGE MOVES OVER THE AREA AND RADIATIONAL COOLING
TAKES PLACE OVER A FRESH SNOW FIELD. AIR TEMPERATURES AROUND 12Z
FRIDAY SHOULD RANGE FROM -18 OVER THE FAR NORTH TO -5 IN THE
SOUTHEAST. WILL KEEP THE WIND CHILL HEADLINES AS THEY ARE WITH
VALUES FROM -25 TO -35 COMMON IN THE WARNING AREA. AREAS WITHIN THE
ADVISORY WILL SEE -15 TO -25.

AS THE SURFACE HIGH MOVES EAST LATER FRIDAY...WARM ADVECTION WILL
SET UP AHEAD OF THE NEXT ALBERTA CLIPPER THAT IS EXPECTED TO TRACK
FROM MINNESOTA FRIDAY NIGHT ACROSS FAR NORTHERN ILLINOIS ON
SATURDAY. QPF SHOULD NOT BE HIGH DUE TO THE COMPLETE LACK OF
MOISTURE...BUT A FEW TENTHS INCH OF SNOW COULD BE SHAKEN OUT OVER
THE NORTH. WILL HAVE SOME LOW-END CHANCE POPS IN THE NORTH FOR
FRIDAY NIGHT & SATURDAY...THEN SLIGHT CHANCE IN THE EAST SATURDAY
NIGHT.

LONG TERM...SUNDAY THROUGH WEDNESDAY...
THE OVERALL UPPER PATTERN FEATURING A LONG-WAVE TROUGH OVER THE
EASTERN CONUS WILL CONTINUE INTO EARLY NEXT WEEK. BY TUESDAY AND
WEDNESDAY...THIS TROUGH WILL BE MOVING EAST AND WILL ALLOW HIGHER
HEIGHTS AND WARMER TEMPERATURES TO RETURN TO THE REGION. BEFORE THE
TROUGH MOVES OUT THOUGH...MODELS HAVE BEEN HINTING AS ONE LAST
CLIPPER TO COME SOUTHEASTWARD TOWARD ILLINOIS IN THE GENERAL SUNDAY
NIGHT/MONDAY TIME FRAME. WILL HAVE SOME SLIGHT CHANCE POPS IN THE
NORTH SUNDAY NIGHT FOR LIGHT SNOW IN THE WARM ADVECTION PATTERN
AHEAD OF THE SURFACE LOW...THEN DRY AFTERWORDS. TEMPERATURES WILL BE
ON A WARMING TREND...WITH 25-30 DEGREES ON SUNDAY RISING TO 35-40 BY
NEXT WEDNESDAY.

04

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 12 PM CST FRIDAY FOR ILZ049>057-
061>063-066>068-071>073.

WIND CHILL WARNING UNTIL 12 PM CST FRIDAY FOR ILZ027>031-036>038-
040>048.

&&

$$

000
FXUS63 KLOT 150056
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
656 PM CST WED JAN 14 2009

.DISCUSSION...
656 PM CST

IZZI

.PREV DISCUSSION...
256 PM CST

MAIN CONCERN IN THE SHORT TERM IS ON THE LAKE EFFECT SNOW BAND
EYING UP NORTHWEST INDIANA AND COOK COUNTY WHILE NOT MANY CHANGES
MADE TO THE COLD WEATHER HEADLINES EXCEPT THAT THE WIND CHILL
WARNING START TIME WILL BE PUSHED UP TO 6PM TONIGHT.

FAIRLY POTENT LAKE EFFECT BAND HAS SET ACROSS THE LAKE ARCING
FROM LUDINGTON MICHIGAN ON DOWN TOWARD CHICAGO AS SFC WINDS HAVE
BEEN FAIRLY CONVERGENT WITH EASTERLIES ON THE EAST SIDE OF THE
LAKE AND NORTHWESTERLIES ON THE WEST SIDE. WITH THE
NORTHWESTERLIES BEING MUCH STRONGER THAN THE EASTERLIES...AM
EXPECTING THIS BAND TO SLOWLY SHIFT EAST LATE THIS AFTERNOON AND
START TAKING AIM AT NORTHWEST INDIANA. THE 18Z NAM 1000-700MB
OMEGA FIELD BACKS UP THIS SHIFT AS WELL. THESE SNOW BANDS ARE
EXPECTED TO BE FAIRLY INTENSE AT TIMES AND SHOULD BOLSTER THE
PREVIOUS 3 TO 5 INCHES THAT HAD PREVIOUSLY FALLEN ACROSS SOUTHERN
COOK...LAKE...AND PORTER COUNTIES UP INTO VERIFYING THE WINTER
STORM WARNING WITH AN EXTRA 3 INCHES FALLING...POSSIBLY MORE
RIGHT ALONG THE LAKE. WILL LIKELY BE EXTENDING THE LAKE COUNTY
WARNING THROUGH THE EARLY EVENING HOURS AS THE BAND SHIFTS
EASTWARD AND LIKELY WONT CLEAR TIL LATER TONIGHT. MODEL GUIDANCE
SUGGESTS THAT THIS BAND SHOULD THEN CLEAR PORTER COUNTY AROUND
MIDNIGHT...SO WILL KEEP THAT END TIME FOR THE WSW GOING AS IS AND
LET THE COOK COUNTY WARNING EXPIRE AT 4PM.

NEXT MAIN WEATHER CONCERN SHIFTS TO THE PLUNGING TEMPERATURES AND
RESULTANT LOW WIND CHILLS. TEMPERATURES HAVE REACHED THEIR MAX FOR
THE DAY AND WILL QUICKLY DROP OFF THIS EVENING AS THE SFC/850MB LOW
PROPAGATES OFF TO THE EAST INTO OHIO. WITH CLEAR SKIES AND A FRESH
SNOW PACK...TEMPS SHOULD DROP BELOW ZERO BY EARLY EVENING WITH
WIND CHILLS DROPPING AS A RESULT OF GUSTY NORTHWESTERLY WINDS.
HAVE BUMPED UP THE WIND CHILL WARNING TO 6PM TONIGHT FROM ITS
PREVIOUS START TIME OF MIDNIGHT DUE TO WIND CHILLS EXPECTED TO BE
BELOW -20F BY 6PM AND -30F SHORTLY THEREAFTER. HAVE NOT TINKERED
MUCH WITH THE PREVIOUSLY FORECAST TEMPS AS THEY ALL SEEM IN ORDER
WITH THE MASSIVE RIDGE OF HIGH PRESSURE DROPPING DOWN ACROSS THE
PLAINS AND MIDWEST. COLDEST TEMPS WILL COME IN FRIDAY MORNING AS
THE CORE OF THE HIGH PROPAGATES SOUTH OF THE REGION. TEMPS/WIND
CHILLS WILL BEGIN TO IMPROVE ON FRIDAY AS RETURN SOUTHERLY FLOW
WILL BRING WARMER AIR BACK INTO THE REGION.

ANOTHER CONCERN FOR TONIGHT IS WITH THE BLOWING AND DRIFTING SNOW
THAT IS EXPECTED WITH THE STRONG NORTHWESTERLY WINDS AND A FRESH
SNOWPACK. SNOW TO LIQUID RATIOS WERE VERY LIGHT WITH THIS LATEST
SNOWFALL...ON THE ORDER OF 30 TO 1...SO ANY KIND OF WIND WILL
LIKELY BLOW THIS SNOW AROUND. WILL BE KEEPING THE WINTER WEATHER
ADVISORY IN EFFECT THROUGH TONIGHT AND MAY NEED TO EXTEND AFTER
MIDNIGHT IF THE WINDS KEEP UP.

FRI NIGHT THROUGH WED...
1256 PM CST
ANOTHER SHORT WAVE IS FORECAST TO DROP INTO THE WESTERN GREAT LAKES
FRIDAY NIGHT AND SATURDAY. IMPRESSIVE WARM AIR ADVECTION PATTERN
SETS UP FRIDAY NIGHT AND HAVE BUMPED POPS UP TO 50 TO 60 PERCENT.
LOW TEMPERATURE WILL LIKELY OCCUR IN THE EARLY EVENING THEN RISE
OVERNIGHT AS ARCTIC AIR MASS RETREATS. QPF OF ONE OR TWO TENTHS
LIQUID AND COLD AIR MASS COULD PRODUCE A COUPLE INCHES OF
SNOW...MAINLY NORTH. AT THIS POINT IT LOOKS LIKE IT WILL BE BELOW
HEADLINE CRITERIA. A CHANCE OF SNOW LINGERING THROUGH SATURDAY AS
VORT MAX SWINGS THROUGH NORTHERN IL. COULD BE A COUPLE MORE SHORT
WAVES DROPPING DOWN SATURDAY NIGHT INTO MONDAY BUT DETAILS AND
TIMING ARE MUDDY...SO WILL JUST MAINTAIN SOME LOW POPS FOR NOW.
OVERALL TREND OF GFS AND ECMWF IS FOR WESTERN US RIDGE TO
EVENTUALLY SHIFT EAST INTO THE MIDWEST EARLY TO MID WEEK. SHOULD
FINALLY SEE A PERIOD OF TRANQUIL WEATHER TUE AND WED WITH
TEMPERATURES EVENTUALLY MODERATING TO THE FREEZING MARK BY
WEDNESDAY.

ALLSOPP

HALBACH

.AVIATION...
620 PM CST

00Z TAFORS...H5 SHORT WAVE ROTATING THROUGH MEAN UPPER TROF
CURRENTLY CROSSING SOUTHERN WI AND NORTHERN IL PRODUCING ANOTHER
PD OF -SN. THIS PRECIP TO BE ENDING BY 01Z AT KORD & KMDW AS TROF
AXIS PASSES BY. SKY CONDITION GOING CLEAR QUICKLY BEHIND TROF
PASSAGE WITH SUBSIDENCE AND LOW LEVEL DRYING.

SOUTHERN END OF LAKE EFFECT PLUME WITH EMBEDDED MESO LOWS HAS
CONTINUED TO SHIFT FROM JUST OFF THE IL SHORELINE TO EAST OF KGYY
OVER THE LAST FEW HRS AND WILL CONTINUE TREND TO OTHER SIDE OF
LAKE DURING THE EVENING.

STRONG PRES RISE CENTER BEHIND SFC LOW IN OH AND STRONG RIDGE
BUILDING FM THE NORTHERN PLAINS TO THE MID MS VALLEY NOW OVER SW
IND...FAR SOUTHERN IL...SE MO. WHILE A MODERATELY STRONG GRADIENT
PERSISTS ACROSS THE LOCAL TERMINALS TONIGHT WINDS JUST UPSTREAM
HAVE ALREADY FALLEN OFF TO 6-12KTS WITH RAPID DECOUPLING OF SFC
OVER DEEP FRESH SNOW COVER UNDER SKC. PERSISTENT VSBY RESTRICTIONS
DUE TO BLSN NOT ANTICIPATED AND ANY BRIEF LOCAL REDUCTIONS TO
END EARLY EVE WITH DECREASING WINDS.

WITH CENTER OF SFC ANTICYCLONE PROGGED TO SETTLE TO OVER THE MID
MO VALLEY BY LATE THU AFTERNOON SFC WINDS AT LOCAL TERMINALS TO
BACK A BIT TO WNW-W IN RESPONSE.

TRS

.MARINE...

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-
ILZ022-ILZ023-ILZ032-ILZ033-ILZ039 UNTIL MIDNIGHT THURSDAY.

WIND CHILL WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
ILZ023-ILZ032-ILZ033-ILZ039 UNTIL NOON FRIDAY.

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL
NOON FRIDAY.

WINTER STORM WARNING...INZ001 UNTIL 9 PM WEDNESDAY.

WINTER WEATHER ADVISORY...INZ001 UNTIL MIDNIGHT THURSDAY.

WINTER STORM WARNING...INZ002 UNTIL MIDNIGHT THURSDAY.

WINTER WEATHER ADVISORY...INZ010-INZ011-INZ019 UNTIL MIDNIGHT
THURSDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ744-LMZ745-
LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 6 AM
THURSDAY.

HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878
UNTIL 6 AM SATURDAY.

HEAVY FREEZING SPRAY WARNING...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL
10 AM THURSDAY.

SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 10 AM
THURSDAY.

HEAVY FREEZING SPRAY WARNING...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL NOON THURSDAY.

000
FXUS63 KLOT 150024
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
624 PM CST WED JAN 14 2009

.DISCUSSION...
256 PM CST

ALLSOPP

HALBACH

.AVIATION...
620 PM CST

WITH CENTER OF SFC ANTICYCLONE PROGGED TO SETTLE TO OVER THE MID
MO VALLEY BY LATE THU AFTERNOON SFC WINDS AT LOCAL TERMINALS TO
BACK A BIT TO WNW-W IN RESPONSE.

TRS

.MARINE...

WIND CHILL WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
ILZ023-ILZ032-ILZ033-ILZ039 UNTIL NOON FRIDAY.

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL
NOON FRIDAY.

WINTER STORM WARNING...INZ001 UNTIL 9 PM WEDNESDAY.

WINTER WEATHER ADVISORY...INZ001...9 PM WEDNESDAY TO MIDNIGHT
THURSDAY.

WINTER STORM WARNING...INZ002 UNTIL MIDNIGHT THURSDAY.

WINTER WEATHER ADVISORY...INZ010-INZ011-INZ019 UNTIL MIDNIGHT
THURSDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ744-LMZ745-
LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 6 AM
THURSDAY.

HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878
UNTIL 6 AM SATURDAY.

HEAVY FREEZING SPRAY WARNING...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL
10 AM THURSDAY.

SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 10 AM
THURSDAY.

HEAVY FREEZING SPRAY WARNING...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL NOON THURSDAY.


000
FXUS63 KILX 142344
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
544 PM CST WED JAN 14 2009

.DISCUSSION...
ISSUED 300 PM CST WED JAN 14 2009

SHORT TERM...TONIGHT THROUGH SATURDAY...
SURFACE LOW MOVED RAPIDLY THROUGH CENTRAL ILLINOIS TODAY AND IS
ALREADY INTO EASTERN INDIANA. MOST OF THE ACCUMULATING SNOW HAS
ENDED OVER THE AREA...BUT STRONG WINDS ALONG WITH THE POWDERY SNOW
WILL MAKE FOR REDUCED VISIBILITIES AND DIFFICULT TRAVEL AT LEAST
THROUGH THE AFTERNOON COMMUTE. WILL THEREFORE KEEP THE WINTER
WEATHER ADVISORY FOR BLOWING SNOW GOING UNTIL 6 PM...AND IT CAN BE
EXTENDED IF POOR VISIBILITIES CONTINUE ANY LONGER.

LARGE 1046 MB SURFACE HIGH IS CENTERED JUST NORTH OF NORTH DAKOTA
AND IT WILL DIVE SOUTHEASTWARD TO WESTERN IOWA BY THIS TIME ON
THURSDAY. BITTERLY COLD AIR WILL BECOME ENTRENCHED OVER THE MIDWEST
AND WILL BE SLOW TO ERODE AWAY. TEMPERATURES BY DAWN TONIGHT WILL
LIKELY REACH -15 OVER THE FAR NORTH...AND 0-5 ABOVE IN THE
SOUTHEAST. EVEN COLDER TEMPERATURES ARE EXPECTED FRIDAY MORNING AS
THE CENTER OF THE RIDGE MOVES OVER THE AREA AND RADIATIONAL COOLING
TAKES PLACE OVER A FRESH SNOW FIELD. AIR TEMPERATURES AROUND 12Z
FRIDAY SHOULD RANGE FROM -18 OVER THE FAR NORTH TO -5 IN THE
SOUTHEAST. WILL KEEP THE WIND CHILL HEADLINES AS THEY ARE WITH
VALUES FROM -25 TO -35 COMMON IN THE WARNING AREA. AREAS WITHIN THE
ADVISORY WILL SEE -15 TO -25.

AS THE SURFACE HIGH MOVES EAST LATER FRIDAY...WARM ADVECTION WILL
SET UP AHEAD OF THE NEXT ALBERTA CLIPPER THAT IS EXPECTED TO TRACK
FROM MINNESOTA FRIDAY NIGHT ACROSS FAR NORTHERN ILLINOIS ON
SATURDAY. QPF SHOULD NOT BE HIGH DUE TO THE COMPLETE LACK OF
MOISTURE...BUT A FEW TENTHS INCH OF SNOW COULD BE SHAKEN OUT OVER
THE NORTH. WILL HAVE SOME LOW-END CHANCE POPS IN THE NORTH FOR
FRIDAY NIGHT & SATURDAY...THEN SLIGHT CHANCE IN THE EAST SATURDAY
NIGHT.

LONG TERM...SUNDAY THROUGH WEDNESDAY...
THE OVERALL UPPER PATTERN FEATURING A LONG-WAVE TROUGH OVER THE
EASTERN CONUS WILL CONTINUE INTO EARLY NEXT WEEK. BY TUESDAY AND
WEDNESDAY...THIS TROUGH WILL BE MOVING EAST AND WILL ALLOW HIGHER
HEIGHTS AND WARMER TEMPERATURES TO RETURN TO THE REGION. BEFORE THE
TROUGH MOVES OUT THOUGH...MODELS HAVE BEEN HINTING AS ONE LAST
CLIPPER TO COME SOUTHEASTWARD TOWARD ILLINOIS IN THE GENERAL SUNDAY
NIGHT/MONDAY TIME FRAME. WILL HAVE SOME SLIGHT CHANCE POPS IN THE
NORTH SUNDAY NIGHT FOR LIGHT SNOW IN THE WARM ADVECTION PATTERN
AHEAD OF THE SURFACE LOW...THEN DRY AFTERWORDS. TEMPERATURES WILL BE
ON A WARMING TREND...WITH 25-30 DEGREES ON SUNDAY RISING TO 35-40 BY
NEXT WEDNESDAY.

04

&&

.AVIATION...
ISSUED 543 PM CST WED JAN 14 2009...FOR THE 00Z TAFS

THE CLIPPER IS PULLING AWAY TO THE EAST. THE LOW CENTER HAS
REACHED SW OHIO. PRESSURE RISES ARE WEAKENING IN OUR WESTERN
CWA...WHICH IS HELPING TO KEEP GUSTS DOWN INTO THE LOWER 20KT RANGE.
BMI/CMI/DEC WILL REMAIN IN THE TIGHTER PRES GRADIENT FOR A FEW
MORE HOURS. STILL...WINDS WILL REMAIN STEADY EVERYWHERE OVERNIGHT
WITH SUSTAINED WINDS IN THE 12 TO 15KT RANGE.

WILL KEEP TEMPO/S FOR MVFR VIS DUE TO BLSN AND ISOLATED SNOW
SHOWERS FOR THE FIRST PART OF THE EVENING AT ALL SITES BUT PIA.
SATELLITE PICS SHOW THE MAJORITY OF CLOUD BANDS AND SNOW SHOWERS
HAVE DISSIPATED...BUT BMI/DEC/CMI MAY SEE THEM THROUGH MID EVENING.

SKIES SHOULD CLEAR OUT AFTER MIDNIGHT...WITH STEADY NW WINDS. A
FEW GUSTS TO 20KT ARE EXPECTED THUR AFTERNOON...SO I ADDED THAT TO
THE 00Z TAFS.

SHIMON
&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 12 PM CST FRIDAY FOR ILZ049>057-
061>063-066>068-071>073.

WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR
ILZ027>031-036>038-040>057-061.

WIND CHILL WARNING UNTIL 12 PM CST FRIDAY FOR ILZ027>031-036>038-
040>048.

&&

$$


000
FXUS63 KILX 142100
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
300 PM CST WED JAN 14 2009

.DISCUSSION...
ISSUED 300 PM CST WED JAN 14 2009

SHORT TERM...TONIGHT THROUGH SATURDAY...
SURFACE LOW MOVED RAPIDLY THROUGH CENTRAL ILLINOIS TODAY AND IS
ALREADY INTO EASTERN INDIANA. MOST OF THE ACCUMULATING SNOW HAS
ENDED OVER THE AREA...BUT STRONG WINDS ALONG WITH THE POWDERY SNOW
WILL MAKE FOR REDUCED VISIBILITIES AND DIFFICULT TRAVEL AT LEAST
THROUGH THE AFTERNOON COMMUTE. WILL THEREFORE KEEP THE WINTER
WEATHER ADVISORY FOR BLOWING SNOW GOING UNTIL 6 PM...AND IT CAN BE
EXTENDED IF POOR VISIBILITIES CONTINUE ANY LONGER.

LARGE 1046 MB SURFACE HIGH IS CENTERED JUST NORTH OF NORTH DAKOTA
AND IT WILL DIVE SOUTHEASTWARD TO WESTERN IOWA BY THIS TIME ON
THURSDAY. BITTERLY COLD AIR WILL BECOME ENTRENCHED OVER THE MIDWEST
AND WILL BE SLOW TO ERODE AWAY. TEMPERATURES BY DAWN TONIGHT WILL
LIKELY REACH -15 OVER THE FAR NORTH...AND 0-5 ABOVE IN THE
SOUTHEAST. EVEN COLDER TEMPERATURES ARE EXPECTED FRIDAY MORNING AS
THE CENTER OF THE RIDGE MOVES OVER THE AREA AND RADIATIONAL COOLING
TAKES PLACE OVER A FRESH SNOW FIELD. AIR TEMPERATURES AROUND 12Z
FRIDAY SHOULD RANGE FROM -18 OVER THE FAR NORTH TO -5 IN THE
SOUTHEAST. WILL KEEP THE WIND CHILL HEADLINES AS THEY ARE WITH
VALUES FROM -25 TO -35 COMMON IN THE WARNING AREA. AREAS WITHIN THE
ADVISORY WILL SEE -15 TO -25.

AS THE SURFACE HIGH MOVES EAST LATER FRIDAY...WARM ADVECTION WILL
SET UP AHEAD OF THE NEXT ALBERTA CLIPPER THAT IS EXPECTED TO TRACK
FROM MINNESOTA FRIDAY NIGHT ACROSS FAR NORTHERN ILLINOIS ON
SATURDAY. QPF SHOULD NOT BE HIGH DUE TO THE COMPLETE LACK OF
MOISTURE...BUT A FEW TENTHS INCH OF SNOW COULD BE SHAKEN OUT OVER
THE NORTH. WILL HAVE SOME LOW-END CHANCE POPS IN THE NORTH FOR
FRIDAY NIGHT & SATURDAY...THEN SLIGHT CHANCE IN THE EAST SATURDAY
NIGHT.

LONG TERM...SUNDAY THROUGH WEDNESDAY...
THE OVERALL UPPER PATTERN FEATURING A LONG-WAVE TROUGH OVER THE
EASTERN CONUS WILL CONTINUE INTO EARLY NEXT WEEK. BY TUESDAY AND
WEDNESDAY...THIS TROUGH WILL BE MOVING EAST AND WILL ALLOW HIGHER
HEIGHTS AND WARMER TEMPERATURES TO RETURN TO THE REGION. BEFORE THE
TROUGH MOVES OUT THOUGH...MODELS HAVE BEEN HINTING AS ONE LAST
CLIPPER TO COME SOUTHEASTWARD TOWARD ILLINOIS IN THE GENERAL SUNDAY
NIGHT/MONDAY TIMEFRAME. WILL HAVE SOME SLIGHT CHANCE POPS IN THE
NORTH SUNDAY NIGHT FOR LIGHT SNOW IN THE WARM ADVECTION PATTERN
AHEAD OF THE SURFACE LOW...THEN DRY AFTERWARDS. TEMPERATURES WILL BE
ON A WARMING TREND...WITH 25-30 DEGREES ON SUNDAY RISING TO 35-40 BY
NEXT WEDNESDAY.

04
&&

.AVIATION...
ISSUED 1150 AM CST WED JAN 14 2009

EXPECT STRONG NW WINDS OF 15 TO 20 KTS WITH GUSTS OF 25 TO 35 KTS
THIS AFTERNOON AND EARLY EVENING DIMINISHING TO 12 TO 15 KTS
OVERNIGHT INTO THU MORNING. MVFR CEILINGS AND VISBYS WITH LIGHT SNOW
SHOWERS AND BLOWING SNOW THIS AFTERNOON ESPECIALLY ALONG I-74. BMI
AND PIA CURRENTLY HAVING 600 AN 900 FT CEILINGS RESPECTIVELY. STRONG
NW WINDS ALSO GENERATING BLOWING SNOW ESPECIALLY OVER DEEPER 4 TO 6
INCH SNOW COVER ALONG I-74. LOW CLOUDS WILL CLEAR FROM THE WEST
BETWEEN 02Z AND 06Z STARTING AT PIA FIRST AND LAST AT CMI.

1012 MB LOW PRESSURE OVER EAST CENTRAL IL JUST EAST OF RANTOUL AND
ITS COLD FRONT IS NEAR I-57. MODELS WEAKEN LOW PRESSURE AS IT MOVES
TO NEAR THE OH/KY/WV BORDER BY 00Z/6 PM AND OFF THE MID ATLANTIC
COAST BY DAWN THU. 1046 MB VERY STRONG ARCTIC HIGH PRESSURE OVER
SASKETCHEWAN WILL STRENGTHEN TO 1049 MB AS IT BUILDS INTO THE
CENTRAL PLAINS THU MORNING. THIS SHOULD CLEAR LOW CLOUDS FROM THE
WEST DURING MID/LATE EVENING WHILE DIMINISHING NW WINDS.

HUETTL
&&

.CLIMATE...
ISSUED 300 PM CST WED JAN 14 2009

ALTHOUGH THE ARCTIC AIRMASS COMING INTO THE MIDWEST WILL BE THE
COLDEST OF THE SEASON SO FAR...IT DOES NOT APPEAR THAT ANY RECORD
LOWS WILL BE THREATENED. HERE ARE THE STANDING RECORD LOW
TEMPERATURES FOR A FEW LOCATIONS OVER THE FORECAST AREA...

CITY...RECORD LOW TONIGHT...RECORD LOW THURSDAY NIGHT

PEORIA...-22 IN 1979...-20 IN 1977
SPRINGFIELD...-17 IN 1888...-20 IN 1977
LINCOLN...-34 IN 1977...-19 IN 1977
URBANA...-18 IN 1893...-17 IN 1977
GALESBURG...-21 IN 1994...-20 IN 1977

THE RECORD LOW OF -34 FOR LINCOLN TONIGHT IS ALSO THE ALL-TIME
RECORD LOW TEMPERATURE FOR LINCOLN.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR
ILZ027>031-036>038-040>057-061.

WIND CHILL WARNING FROM 6 PM THIS EVENING TO 12 PM CST FRIDAY FOR
ILZ027>031-036>038-040>048.

WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 12 PM CST FRIDAY
FOR ILZ049>057-061>063-066>068-071>073.
&&

$$

000
FXUS63 KLOT 142056
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
256 PM CST WED JAN 14 2009

.DISCUSSION...
256 PM CST

ALLSOPP

HALBACH

.AVIATION...

UPDATE 212 PM...HAVE SENT AMENDMENTS SINCE THE 18Z TAFS TO SHOW A
MUCH FASTER CLEARING TREND AS MVFR CIGS ARE QUICKLY SHIFTING
SOUTHEAST. STILL A POSSIBILITY OF SOME LAKE CLOUDS ALONG THE SHORE
AS WELL AS SOME SCT/BKN 3-5KFT CLOUDS MOVING THROUGH THE AREA THRU
EARLY EVENING. LAKE EFFECT BAND/PLUME MAINLY OFFSHORE AND APPEARS
IT WILL REMAIN EAST OF ORD/MDW...AFFECTING GYY THRU EARLY EVENING
AS IS SHIFTS EAST. WINDS GUSTING 20-25KTS AND WHILE BLOWING SNOW
MAY NOT CAUSE SIGNIFICANT RESTRICTIONS TO THE VISIBILITIES...
ESPECIALLY IF IT IS LOWER THAN THE VIS SENSORS CAN DETECT...SOME
4-6SM VISIBILITIES ARE STILL POSSIBLE. CMS

PREVIOUS DISCUSSION...

18Z TAFS...OVERALL...GOING FORECAST IN GOOD SHAPE WITH NO MAJOR
CHANGES. SFC LOW OVER EASTERN ILLINOIS WILL MOVE EAST ACROSS THE
OHIO VALLEY THIS AFTERNOON. BAND OF SNOW ON THE NORTH SIDE OF THIS
SYSTEM IS FINALLY MOVING EAST/SOUTHEAST. VIS RESTRICTIONS PARTLY
DUE TO FOG/MIST BUT SOME LIGHT SNOW/FLURRIES WILL CONTINUE FOR A
FEW MORE HRS.

ATTENTION SHIFTS TO LAKE EFFECT PLUME FORMING OVER CENTRAL LAKE
MICHIGAN. LATEST RADAR IMAGES SHOW THIS BAND BEGINNING TO SHIFT
SOUTHEAST. THIS BAND WILL CONTINUE TO SHIFT EAST THRU THE
AFTERNOON. NOT SURE IF IT WILL IMPACT ORD...BETTER CHANCE AT MDW
BUT SHORT DURATION IF IT DOES. PREVIOUS FORECAST HANDLED THIS
WITH A TEMPO AND THAT SEEMS REASONABLE TO CONTINUE AND CAN AMEND
TO REMOVE IF THE BAND SHIFTS EAST SOONER. THIS WILL LIKELY IMPACT
GYY THE MOST OF ALL THE TAFS AND HAVE CONTINUED WITH 1/2SM AND
MODERATE SNOW THRU LATE AFTERNOON.

WINDS HAVE SHIFTED NORTHERLY WITH GUSTS 20-25KTS OVER NORTHWEST
IL. STRONGEST WINDS WILL AFFECT AREAS ACROSS CENTRAL IL JUST
BEHIND THE SFC LOW. BUT EXPECT GUSTS 20-25KTS TO CONTINUE...ONCE
THEY DEVELOP...THRU THE EVENING HRS AND BEGIN TO RELAX TO 18-20KTS
OVERNIGHT. WINDS WILL GRADUALLY TURN NORTHWEST THIS EVENING AND
MORE WESTERLY THURSDAY MORNING. SNOW HAS BEEN VERY DRY AND FLUFFY
AND EVEN AT THESE WIND SPEEDS...EXPECT SOME BLOWING/DRIFTING SNOW
AND PREVAILING MVFR VISIBILITIES LOOK GOOD...THOUGH THEY COULD
OCCASIONALLY DROP LOWER...ESPECIALLY LATER THIS AFTERNOON AND THIS
EVENING.

CIGS GENERALLY MVFR BETWEEN 1-2KFT BUT THEY QUICKLY LIFT/SCATTER
ACROSS SOUTHWEST WI AND EASTERN IA. SOUNDINGS/RH FIELDS INDICATE
POTENTIAL FOR CIGS IN THIS RANGE THROUGH THE LATE EVENING...THEN
SCATTERING OUT AFTER MIDNIGHT. DECIDED TO JUST LEAVING THE GOING
CIGS AS IS BUT THEY COULD SCATTER OUT SOONER OR LIFT HIGHER THAN
NEW FORECAST INDICATES. CMS

.MARINE...

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER STORM WARNING...ILZ014 UNTIL 4 PM WEDNESDAY.

WINTER WEATHER ADVISORY...ILZ014 UNTIL MIDNIGHT THURSDAY.

WIND CHILL WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
ILZ023-ILZ032-ILZ033-ILZ039...MIDNIGHT THURSDAY TO NOON
FRIDAY.

WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ022-
ILZ023-ILZ032-ILZ033-ILZ039 UNTIL MIDNIGHT THURSDAY.

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-
INZ019...MIDNIGHT THURSDAY TO NOON FRIDAY.

WINTER STORM WARNING...INZ001 UNTIL 4 PM WEDNESDAY.

WINTER WEATHER ADVISORY...INZ001 UNTIL MIDNIGHT THURSDAY.

WINTER STORM WARNING...INZ002 UNTIL MIDNIGHT THURSDAY.

WINTER WEATHER ADVISORY...INZ010-INZ011-INZ019 UNTIL MIDNIGHT
THURSDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 6 AM THURSDAY.

HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878
UNTIL 6 AM SATURDAY.

HEAVY FREEZING SPRAY WARNING...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL
10 AM THURSDAY.

SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 10 AM
THURSDAY.

GALE WARNING...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 6 AM THURSDAY.

HEAVY FREEZING SPRAY WARNING...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL NOON THURSDAY.


000
FXUS63 KLOT 142012
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
212 PM CST WED JAN 14 2009

.DISCUSSION...
1256 PM CST

FRI NIGHT THROUGH WED...
ANOTHER SHORT WAVE IS FORECAST TO DROP INTO THE WESTERN GREAT LAKES
FRIDAY NIGHT AND SATURDAY. IMPRESSIVE WARM AIR ADVECTION PATTERN
SETS UP FRIDAY NIGHT AND HAVE BUMPED POPS UP TO 50 TO 60 PERCENT.
LOW TEMPERATURE WILL LIKELY OCCUR IN THE EARLY EVENING THEN RISE
OVERNIGHT AS ARCTIC AIR MASS RETREATS. QPF OF ONE OR TWO TENTHS
LIQUID AND COLD AIR MASS COULD PRODUCE A COUPLE INCHES OF
SNOW...MAINLY NORTH. AT THIS POINT IT LOOKS LIKE IT WILL BE BELOW
HEADLINE CRITERIA. A CHANCE OF SNOW LINGERING THROUGH SATURDAY AS
VORT MAX SWINGS THROUGH NORTHERN IL. COULD BE A COUPLE MORE SHORT
WAVES DROPPING DOWN SATURDAY NIGHT INTO MONDAY BUT DETAILS AND
TIMING ARE MUDDY...SO WILL JUST MAINTAIN SOME LOW POPS FOR NOW.
OVERALL TREND OF GFS AND ECMWF IS FOR WESTERN US RIDGE TO
EVENTUALLY SHIFT EAST INTO THE MIDWEST EARLY TO MID WEEK. SHOULD
FINALLY SEE A PERIOD OF TRANQUIL WEATHER TUE AND WED WITH
TEMPERATURES EVENTUALLY MODERATING TO THE FREEZING MARK BY
WEDNESDAY.

ALLSOPP

&&

.AVIATION...

UPDATE 212 PM...HAVE SENT AMENDMENTS SINCE THE 18Z TAFS TO SHOW A
MUCH FASTER CLEARING TREND AS MVFR CIGS ARE QUICKLY SHIFTING
SOUTHEAST. STILL A POSSIBILITY OF SOME LAKE CLOUDS ALONG THE SHORE
AS WELL AS SOME SCT/BKN 3-5KFT CLOUDS MOVING THROUGH THE AREA THRU
EARLY EVENING. LAKE EFFECT BAND/PLUME MAINLY OFFSHORE AND APPEARS
IT WILL REMAIN EAST OF ORD/MDW...AFFECTING GYY THRU EARLY EVENING
AS IS SHIFTS EAST. WINDS GUSTING 20-25KTS AND WHILE BLOWING SNOW
MAY NOT CAUSE SIGNIFICANT RESTRICTIONS TO THE VISIBILITIES...
ESPECIALLY IF IT IS LOWER THAN THE VIS SENSORS CAN DETECT...SOME
4-6SM VISIBILITIES ARE STILL POSSIBLE. CMS

PREVIOUS DISCUSSION...

18Z TAFS...OVERALL...GOING FORECAST IN GOOD SHAPE WITH NO MAJOR
CHANGES. SFC LOW OVER EASTERN ILLINOIS WILL MOVE EAST ACROSS THE
OHIO VALLEY THIS AFTERNOON. BAND OF SNOW ON THE NORTH SIDE OF THIS
SYSTEM IS FINALLY MOVING EAST/SOUTHEAST. VIS RESTRICTIONS PARTLY
DUE TO FOG/MIST BUT SOME LIGHT SNOW/FLURRIES WILL CONTINUE FOR A
FEW MORE HRS.

ATTENTION SHIFTS TO LAKE EFFECT PLUME FORMING OVER CENTRAL LAKE
MICHIGAN. LATEST RADAR IMAGES SHOW THIS BAND BEGINNING TO SHIFT
SOUTHEAST. THIS BAND WILL CONTINUE TO SHIFT EAST THRU THE
AFTERNOON. NOT SURE IF IT WILL IMPACT ORD...BETTER CHANCE AT MDW
BUT SHORT DURATION IF IT DOES. PREVIOUS FORECAST HANDLED THIS
WITH A TEMPO AND THAT SEEMS REASONABLE TO CONTINUE AND CAN AMEND
TO REMOVE IF THE BAND SHIFTS EAST SOONER. THIS WILL LIKELY IMPACT
GYY THE MOST OF ALL THE TAFS AND HAVE CONTINUED WITH 1/2SM AND
MODERATE SNOW THRU LATE AFTERNOON.

WINDS HAVE SHIFTED NORTHERLY WITH GUSTS 20-25KTS OVER NORTHWEST
IL. STRONGEST WINDS WILL AFFECT AREAS ACROSS CENTRAL IL JUST
BEHIND THE SFC LOW. BUT EXPECT GUSTS 20-25KTS TO CONTINUE...ONCE
THEY DEVELOP...THRU THE EVENING HRS AND BEGIN TO RELAX TO 18-20KTS
OVERNIGHT. WINDS WILL GRADUALLY TURN NORTHWEST THIS EVENING AND
MORE WESTERLY THURSDAY MORNING. SNOW HAS BEEN VERY DRY AND FLUFFY
AND EVEN AT THESE WIND SPEEDS...EXPECT SOME BLOWING/DRIFTING SNOW
AND PREVAILING MVFR VISIBILITIES LOOK GOOD...THOUGH THEY COULD
OCCASIONALLY DROP LOWER...ESPECIALLY LATER THIS AFTERNOON AND THIS
EVENING.

CIGS GENERALLY MVFR BETWEEN 1-2KFT BUT THEY QUICKLY LIFT/SCATTER
ACROSS SOUTHWEST WI AND EASTERN IA. SOUNDINGS/RH FIELDS INDICATE
POTENTIAL FOR CIGS IN THIS RANGE THROUGH THE LATE EVENING...THEN
SCATTERING OUT AFTER MIDNIGHT. DECIDED TO JUST LEAVING THE GOING
CIGS AS IS BUT THEY COULD SCATTER OUT SOONER OR LIFT HIGHER THAN
NEW FORECAST INDICATES. CMS

&&

.MARINE...

212 PM...LOW PRESSURE MOVING EAST ACROSS THE OHIO VALLEY THIS
AFTERNOON WILL MOVE OFF THE ATLANTIC COAST THURSDAY MORNING. LARGE
STRONG ARCTIC HIGH PRESSURE WILL BUILD ACROSS THE PLAINS TONIGHT
THEN SPREAD SOUTHEAST ACROSS THE OHIO AND TENNESSEE VALLEYS
THURSDAY AND THURSDAY NIGHT. A PERIOD OF GALES IS LIKELY ACROSS
THE SOUTHERN HALF OF LAKE MICHIGAN TONIGHT AS THE GRADIENT
TIGHTENS BETWEEN THESE TWO FEATURES. WINDS DIMINISH TO 30 KNOTS BY
MORNING BUT GRADIENT LOOKS LIKE IT WILL MAINTAIN 25-30KTS THRU
FRIDAY MORNING BEFORE IT FINALLY WEAKENS. WINDS THEN QUICKLY TURN
SOUTHERLY FRIDAY NIGHT AS ANOTHER CLIPPER SYSTEM MOVES ACROSS THE
WESTERN LAKES WITH WINDS TURNING BACK NORTHERLY SATURDAY. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER STORM WARNING...ILZ014 UNTIL 4 PM WEDNESDAY.

     WINTER WEATHER ADVISORY...ILZ014 UNTIL MIDNIGHT THURSDAY.

     WIND CHILL WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...MIDNIGHT THURSDAY TO NOON
     FRIDAY.

     WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039 UNTIL MIDNIGHT THURSDAY.

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-
     INZ019...MIDNIGHT THURSDAY TO NOON FRIDAY.

     WINTER STORM WARNING...INZ001 UNTIL 4 PM WEDNESDAY.

     WINTER WEATHER ADVISORY...INZ001 UNTIL MIDNIGHT THURSDAY.

     WINTER STORM WARNING...INZ002 UNTIL MIDNIGHT THURSDAY.

     WINTER WEATHER ADVISORY...INZ010-INZ011-INZ019 UNTIL MIDNIGHT
     THURSDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
     LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 6 AM THURSDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
     LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
     LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878
     UNTIL 6 AM SATURDAY.

     HEAVY FREEZING SPRAY WARNING...NEARSHORE WINTHROP HARBOR TO GARY
     IN UNTIL 10 AM THURSDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN
     UNTIL 10 AM THURSDAY.

     GALE WARNING...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 6 AM
     THURSDAY.

     HEAVY FREEZING SPRAY WARNING...NEARSHORE GARY TO MICHIGAN CITY
     IN UNTIL NOON THURSDAY.

&&

$$


000
FXUS63 KLOT 141921
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
121 PM CST WED JAN 14 2009

.DISCUSSION...
1256 PM CST

FRI NIGHT THROUGH WED...
ANOTHER SHORT WAVE IS FORECAST TO DROP INTO THE WESTERN GREAT LAKES
FRIDAY NIGHT AND SATURDAY. IMPRESSIVE WARM AIR ADVECTION PATTERN
SETS UP FRIDAY NIGHT AND HAVE BUMPED POPS UP TO 50 TO 60 PERCENT.
LOW TEMPERATURE WILL LIKELY OCCUR IN THE EARLY EVENING THEN RISE
OVERNIGHT AS ARCTIC AIR MASS RETREATS. QPF OF ONE OR TWO TENTHS
LIQUID AND COLD AIR MASS COULD PRODUCE A COUPLE INCHES OF
SNOW...MAINLY NORTH. AT THIS POINT IT LOOKS LIKE IT WILL BE BELOW
HEADLINE CRITERIA. A CHANCE OF SNOW LINGERING THROUGH SATURDAY AS
VORT MAX SWINGS THROUGH NORTHERN IL. COULD BE A COUPLE MORE SHORT
WAVES DROPPING DOWN SATURDAY NIGHT INTO MONDAY BUT DETAILS AND
TIMING ARE MUDDY...SO WILL JUST MAINTAIN SOME LOW POPS FOR NOW.
OVERALL TREND OF GFS AND ECMWF IS FOR WESTERN US RIDGE TO
EVENTUALLY SHIFT EAST INTO THE MIDWEST EARLY TO MID WEEK. SHOULD
FINALLY SEE A PERIOD OF TRANQUIL WEATHER TUE AND WED WITH
TEMPERATURES EVENTUALLY MODERATING TO THE FREEZING MARK BY
WEDNESDAY.

ALLSOPP

&&

.AVIATION...

...POSSIBLE LAKE EFFECT SNOW SHOWERS THIS AFTERNOON THEN BLOWING
SNOW POSSIBLE THROUGH TONIGHT...

18Z TAFS...OVERALL...GOING FORECAST IN GOOD SHAPE WITH NO MAJOR
CHANGES. SFC LOW OVER EASTERN ILLINOIS WILL MOVE EAST ACROSS THE
OHIO VALLEY THIS AFTERNOON. BAND OF SNOW ON THE NORTH SIDE OF THIS
SYSTEM IS FINALLY MOVING EAST/SOUTHEAST. VIS RESTRICTIONS PARTLY
DUE TO FOG/MIST BUT SOME LIGHT SNOW/FLURRIES WILL CONTINUE FOR A
FEW MORE HRS.

ATTENTION SHIFTS TO LAKE EFFECT PLUME FORMING OVER CENTRAL LAKE
MICHIGAN. LATEST RADAR IMAGES SHOW THIS BAND BEGINNING TO SHIFT
SOUTHEAST. THIS BAND WILL CONTINUE TO SHIFT EAST THRU THE
AFTERNOON. NOT SURE IF IT WILL IMPACT ORD...BETTER CHANCE AT MDW
BUT SHORT DURATION IF IT DOES. PREVIOUS FORECAST HANDLED THIS
WITH A TEMPO AND THAT SEEMS REASONABLE TO CONTINUE AND CAN AMEND
TO REMOVE IF THE BAND SHIFTS EAST SOONER. THIS WILL LIKELY IMPACT
GYY THE MOST OF ALL THE TAFS AND HAVE CONTINUED WITH 1/2SM AND
MODERATE SNOW THRU LATE AFTERNOON.

WINDS HAVE SHIFTED NORTHERLY WITH GUSTS 20-25KTS OVER NORTHWEST
IL. STRONGEST WINDS WILL AFFECT AREAS ACROSS CENTRAL IL JUST
BEHIND THE SFC LOW. BUT EXPECT GUSTS 20-25KTS TO CONTINUE...ONCE
THEY DEVELOP...THRU THE EVENING HRS AND BEGIN TO RELAX TO 18-20KTS
OVERNIGHT. WINDS WILL GRADUALLY TURN NORTHWEST THIS EVENING AND
MORE WESTERLY THURSDAY MORNING. SNOW HAS BEEN VERY DRY AND FLUFFY
AND EVEN AT THESE WIND SPEEDS...EXPECT SOME BLOWING/DRIFTING SNOW
AND PREVAILING MVFR VISIBILITIES LOOK GOOD...THOUGH THEY COULD
OCCASIONALLY DROP LOWER...ESPECIALLY LATER THIS AFTERNOON AND THIS
EVENING.

CIGS GENERALLY MVFR BETWEEN 1-2KFT BUT THEY QUICKLY LIFT/SCATTER
ACROSS SOUTHWEST WI AND EASTERN IA. SOUNDINGS/RH FIELDS INDICATE
POTENTIAL FOR CIGS IN THIS RANGE THROUGH THE LATE EVENING...THEN
SCATTERING OUT AFTER MIDNIGHT. DECIDED TO JUST LEAVING THE GOING
CIGS AS IS BUT THEY COULD SCATTER OUT SOONER OR LIFT HIGHER THAN
NEW FORECAST INDICATES. CMS

&&

.MARINE...
345 AM CST

LOW PRESSURE WILL MOVE FROM THE CENTRAL PLAINS ACROSS THE LOWER OHIO
VALLEY LATER TODAY...WITH WINDS SHIFTING TO THE NORTH AND NORTHWEST
AND INCREASING TO 30 TO 35 KNOTS ACROSS LAKE MICHIGAN THIS
AFTERNOON...WITH FRIGID ARCTIC AIR SPREADING ACROSS THE LAKE. THE
COMBINATION OF STRONG WINDS...HIGH WAVES AND BITTER COLD AIR
TEMPERATURES LEADING TO HEAVY FREEZING SPRAY. HAVE ISSUED HEADLINES
FOR GALES ON SOUTHERN LAKE MICHIGAN AS WELL AS HEAVY FREEZING SPRAY
WARNING FOR ENTIRE LAKE. WINDS WILL EASE BELOW GALE FORCE ON THE
SOUTH END OF THE LAKE LATE TONIGHT...THOUGH APPEARS A PERIOD OF
20-30 KNOT WINDS AND ENTRENCHED ARCTIC AIRMASS WILL CONTINUE PRODUCE
A FREEZING SPRAY THREAT THROUGH FRIDAY/SATURDAY. SOME MODERATION OF
TEMPERATURES EXPECTED BY SATURDAY AS WINDS BACK SOUTH IN ADVANCE OF
LOW PRESSURE EXPECTED TO MOVE ACROSS THE MIDWEST AT THAT TIME.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER STORM WARNING...ILZ014 UNTIL 4 PM WEDNESDAY.

     WINTER WEATHER ADVISORY...ILZ014...4 PM WEDNESDAY TO MIDNIGHT
     THURSDAY.

     WIND CHILL WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...MIDNIGHT THURSDAY TO NOON
     FRIDAY.

     WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039 UNTIL MIDNIGHT THURSDAY.

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-
     INZ019...MIDNIGHT THURSDAY TO NOON FRIDAY.

     WINTER STORM WARNING...INZ001 UNTIL 4 PM WEDNESDAY.

     WINTER WEATHER ADVISORY...INZ001...4 PM WEDNESDAY TO MIDNIGHT
     THURSDAY.

     WINTER STORM WARNING...INZ002 UNTIL MIDNIGHT THURSDAY.

     WINTER WEATHER ADVISORY...INZ010-INZ011-INZ019 UNTIL MIDNIGHT
     THURSDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
     LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 6 AM THURSDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
     LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
     LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878
     UNTIL 6 AM SATURDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ740-LMZ741-LMZ742-LMZ743...4
     PM WEDNESDAY TO 10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...4 PM
     WEDNESDAY TO 10 AM THURSDAY.

     GALE WARNING...LMZ744-LMZ745...4 PM WEDNESDAY TO 6 AM THURSDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ744-LMZ745...4 PM WEDNESDAY TO
     NOON THURSDAY.

&&

$$


000
FXUS63 KILX 141754
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1153 AM CST WED JAN 14 2009

.DISCUSSION...
ISSUED 1045 AM CST WED JAN 14 2009

UPDATED THE FORECAST LATE THIS MORNING TO ADJUST LIGHT SNOW
CHANCES TODAY AND FALLING TEMPERATURES. ALSO INCREASE WINDS A BIT
SOONER AND HAVE BLOWING SNOW LATE THIS MORNING WEST OF HIGHWAY 51
FROM BLOOMINGTON TO DECATUR AND THIS AFTERNOON EAST OF HERE.

15Z/10 AM SURFACE MAP SHOWS 1011 MB LOW PRESSURE OVER CENTRAL IL
JUST NE OF LINCOLN. COLD FRONT HAS PRESSED JUST EAST OF I-55 WITH
INCREASING NNW WINDS BEHIND THE COLD FRONT OF 15 TO 25 MPH AND
GUSTS OF 25 TO 40 MPH. TEMPERATURES ALSO FALLING BEHIND THE COLD
FRONT WITH GALESBURG AND MACOMB DOWN TO 10F. IN WARM SECTOR MILDER
TEMPERATURES ARE IN THE LOWER 30S FROM DECATUR AND TAYLORVILLE
AND ROBINSON SOUTH. LIGHT SHOW SHOWERS CONTINUE NORTH OF I-70 AND
ESPECIALLY NE OF I-74 BETWEEN BLOOMINGTON AND CHAMPAIGN WHERE UP
TO AN ADDITIONAL 1 INCH OF SNOW POSSIBLE BEFORE DIMINISHING TO
FLURRIES IN THE NEXT FEW HOURS. THE I-74 CORRIDOR OVER IL RECEIVED
HEAVIEST SNOWFALL OF 4 TO 6 INCHES SINCE LATE TUESDAY EVENING.

SHORT RANGE MODELS SIMILAR IN TAKING LOW PRESSURE AND WEAKENING TO
1015 MB AS IT MOVES QUICKLY EAST TO NEAR HUNTINGTON ON THE
KY/OH/WV BORDER BY 00Z/6 PM WHILE 1045 MB ARCTIC HIGH PRESSURE
OVER SASKATCHEWAN BUILDING INTO THE CENTRAL PLAINS. THIS TO DRIVE
IN THE COLDEST AIR OF THE SEASON INTO THE MIDWEST THROUGH FRI MORNING.
INCREASING NW WINDS WILL DRIVE WIND CHILLS DOWN TO 15 TO 25 BELOW
ZERO TONIGHT. KEPT WINTER WEATHER ADVISORY NORTH OF I-70 GOING
TODAY.

HUETTL

&&

.AVIATION...
ISSUED 1150 AM CST WED JAN 14 2009

EXPECT STRONG NW WINDS OF 15 TO 20 KTS WITH GUSTS OF 25 TO 35 KTS
THIS AFTERNOON AND EARLY EVENING DIMINISHING TO 12 TO 15 KTS
OVERNIGHT INTO THU MORNING. MVFR CEILINGS AND VISBYS WITH LIGHT
SNOW SHOWERS AND BLOWING SNOW THIS AFTERNOON ESPECIALLY ALONG
I-74. BMI AND PIA CURRENTLY HAVING 600 AN 900 FT CEILINGS
RESPECTIVELY. STRONG NW WINDS ALSO GENERATING BLOWING SNOW
ESPECIALLY OVER DEEPER 4 TO 6 INCH SNOW COVER ALONG I-74. LOW
CLOUDS WILL CLEAR FROM THE WEST BETWEEN 02Z AND 06Z STARTING AT
PIA FIRST AND LAST AT CMI.

1012 MB LOW PRESSURE OVER EAST CENTRAL IL JUST EAST OF RANTOUL AND
ITS COLD FRONT IS NEAR I-57. MODELS WEAKEN LOW PRESSURE AS IT
MOVES TO NEAR THE OH/KY/WV BORDER BY 00Z/6 PM AND OFF THE MID
ATLANTIC COAST BY DAWN THU. 1046 MB VERY STRONG ARCTIC HIGH
PRESSURE OVER SASKETCHEWAN WILL STRENGTHEN TO 1049 MB AS IT BUILDS
INTO THE CENTRAL PLAINS THU MORNING. THIS SHOULD CLEAR LOW CLOUDS
FROM THE WEST DURING MID/LATE EVENING WHILE DIMINISHING NW WINDS.

HUETTL

&&

.PREV DISCUSSION...
ISSUED 235 AM CST WED JAN 14 2009

LATEST SURFACE MAP SHOWED CENTER OF CLIPPER SYSTEM ACROSS SOUTHWEST
IOWA. SNOW HAS BEEN RAPIDLY MOVING ACROSS THE CWA OVERNIGHT...WITH
THE CORE OF THE HEAVIER SNOWS GENERALLY ADVANCING EAST-SOUTHEAST
FROM A GALESBURG TO PEORIA LINE. HOWEVER...REGIONAL MOSAICS
ALREADY SHOWING THE BACK EDGE OF THE SNOW SHIELD APPROACHING WEST
CENTRAL ILLINOIS. TEMPERATURES ACROSS THE AREA HAVE BEEN RISING
OVER THE LAST SEVERAL HOURS AND HAD REACHED INTO THE LOWER 20S
AROUND JACKSONVILLE.

SHORT TERM CONCERNS WITH THE FORECAST INVOLVE THE ENDING OF THE
SNOW AND SUBSEQUENT ISSUES WITH BLOWING SNOW...FOLLOWED BY THE
BITTER COLD WEATHER THE NEXT FEW DAYS.

SHORT TERM...TODAY THROUGH FRIDAY...
LATEST RUC MODEL TAKES SURFACE LOW ACROSS THE CENTER OF THE CWA
BETWEEN 12-18Z THIS MORNING. HEAVIEST STORM TOTAL SNOWS OF AROUND
3-5 INCHES EXPECTED ROUGHLY ALONG THE I-74 CORRIDOR...WITH SOME
LOCALLY HIGHER AMOUNTS. EXPANDED THE WINTER WEATHER ADVISORY
FURTHER SOUTH TO INCLUDE AREAS DOWN TO AROUND I-70...WHERE THE
TRAJECTORY OF THE HEAVIER SNOW BANDS MAY CAUSE SOME PROBLEMS.
HOWEVER...OVERALL SOUTHERN EDGE OF THE SNOW ACCUMULATIONS SHOULD
BE FAIRLY SHARP. WINDS STILL EXPECTED TO REALLY PICK UP LATE
MORNING AND INTO THE AFTERNOON IN TIGHT PRESSURE GRADIENT BEHIND
THE DEPARTING HIGH. WITH THIS SNOW BEING RATHER FLUFFY -- SNOW TO
WATER RATIOS PROBABLY ALONG THE ORDER OF 15-20 TO 1 -- EXPECTING
BLOWING SNOW ISSUES TO DEVELOP. THIS SHOULD BEGIN TO TAPER OFF A
BIT DURING THE EVENING.

NEXT ORDER OF BUSINESS IS WITH WIND CHILL HEADLINES. WIND SPEEDS
EXPECTED TO REMAIN IN THE TEENS THROUGH THE NIGHT AS THE ARCTIC
AIRMASS INVADES THE AREA. WITH THE FRESH SNOW COVER...WENT CLOSE
TO THE COLDER NAM MOS GUIDANCE FOR TEMPERATURES...WHICH BRINGS
LOWS OF -10F OR COLDER ACROSS THE NORTHERN CWA TONIGHT AND ZERO
DEGREES ALL THE WAY DOWN TO I-70. WIND CHILLS ACROSS THE NORTHERN
HALF OF THE CWA EXPECTED TO EASILY REACH WARNING CRITERIA OF -25F
FROM ABOUT MIDNIGHT TONIGHT THROUGH NOON THURSDAY...AND WILL BE
CLOSE THURSDAY NIGHT WITH THE CORE OF THE ARCTIC HIGH JUST TO OUR
WEST. IN ORDER TO SIMPLIFY THINGS...ELECTED TO HAVE A WIND CHILL
WARNING RUNNING FROM 6 PM TONIGHT THROUGH NOON FRIDAY...AS AN
UPGRADE OF THE ORIGINAL ADVISORY IN THIS AREA. HOWEVER...THE
WARNING MAY LATER NEED TO BE DOWNGRADED THURSDAY AFTERNOON.
FURTHER SOUTH...EXPANDED THE WIND CHILL ADVISORY TO COVER THE
REMAINDER OF THE CWA...ALTHOUGH AREAS SOUTH OF I-70 WILL BE
BORDERLINE.

DEPARTURE OF HIGH PRESSURE ON FRIDAY WILL LEAD TO WARM AIR
ADVECTION...WITH AFTERNOON TEMPERATURES RECOVERING INTO THE TEENS
AFTER A BRUTAL START IN THE TEENS BELOW IN SOME AREAS.

LONG TERM...FRIDAY NIGHT THROUGH SUNDAY...

NOT MUCH CHANGE MADE TO THIS PORTION OF THE FORECAST...DUE TO
CONCENTRATION ON THE SHORT TERM PROBLEMS. NAM AND GFS HINTING AT
WAA PRECIPITATION DEVELOPMENT FRIDAY AFTERNOON AND
EVENING...MAINLY TO OUR WEST. BETTER PRECIPITATION CHANCES TO
ACCOMPANY NEXT CLIPPER SYSTEM WHICH WILL ZIP ACROSS THE AREA ON
SATURDAY. MODELS KEEPING MUCH OF THIS PRECIPITATION TO OUR NORTH
AT THIS TIME.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 12 PM CST FRIDAY
FOR ILZ049>057-061>063-066>068-071>073.

WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR
ILZ027>031-036>038-040>057-061.

WIND CHILL WARNING FROM 6 PM THIS EVENING TO 12 PM CST FRIDAY
FOR ILZ027>031-036>038-040>048.

&&

$$


000
FXUS63 KLOT 141744
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1144 AM CST WED JAN 14 2009

.DISCUSSION...
934 AM CST

HAVE EXPANDED THE WINTER STORM WARNING EASTWARD ACROSS THE I-80
CORRIDOR AS THE HEAVIEST BAND HAS SET UP ACROSS THE STRETCH AND
WILL LIKELY CONTINUE THROUGH THE REST OF THE MORNING AS THE SFC
LOW TRACKS FROM WEST CENTRAL ILLINOIS EASTWARD ACROSS THE STATE.
SNOW RATIOS ARE VERY HIGH AT ABOUT 25 TO 1...SO WHILE THERE IS
LITTLE QPF INVOLVED...SNOW AMOUNTS WILL BE INTO WARNING CRITERIA
OF AROUND 6 TO 8 INCHES WITH SOME LOCALLY HIGHER AMOUNTS POSSIBLE
IN THE WARNED COUNTIES. KEPT PORTER COUNTY IN THROUGH MIDNIGHT AS
IT APPEARS THAT LAKE EFFECT SNOW WILL CONTINUE AFTER THE SYSTEM
PASSES. WILL HAVE TO FURTHER ASSESS THE LAKE EFFECT SITUATION THIS
AFTERNOON AS SOME OF THE GUIDANCE HAS BEEN SPINNING UP A SFC LOW
AND PROPAGATING IT DOWN THE LAKE. IF THIS LOW WOBBLES FURTHER
WEST...MAY NEED TO RE-EXPAND THE WARNING BACK INTO LAKE COUNTY.
ALSO AM KEEPING TABS ON SOME LAKE EFFECT SNOW SHOWERS UP IN
SOUTHEAST WISCONSIN THAT MAY TURN SOUTH ACROSS LAKE COUNTY
ILLINOIS.

CONDITIONS WILL GRADUALLY IMPROVE FROM NORTHWEST TO SOUTHEAST THIS
MORNING WITH THE BACK EDGE OF THE SNOW ALREADY ACROSS NORTHWEST
ILLINOIS.

HALBACH

PREVIOUS DISCUSSION...
720 AM CST

A FOCUSED FRONTOGENETIC BAND...COMBINED WITH MORE FAVORABLE
DENDRITIC SNOW GROWTH HAS LED SNOW ACCUMULATIONS AROUND 5 INCHES
THROUGH 630 AM...IN A NARROW AXIS ROUGHLY ALONG THE INTERSTATE 80
CORRIDOR IN NORTH CENTRAL ILLINOIS FROM NORTHERN LA SALLE THROUGH
GRUNDY AND KENDALL COUNTIES. THE BACK EDGE OF THE SNOW IS STILL
BACK ACROSS THE MISSISSIPPI RIVER. SNOW RATES SHOULD BEGIN TO
TAPER OFF SOMEWHAT AS ISENTROPIC UPGLIDE BEGINS TO WEAKEN THIS
MORNING...BUT WITH FRONTOGENETIC FORCING PERSISTING THROUGH MID
MORNING MAY SEE AN ADDITIONAL 1 TO 3 INCHES OF ACCUMULATION ALONG
INTERSTATE 80 CORRIDOR IN NORTHEAST ILLINOIS BRINGING STORM TOTAL
SNOW ACCUMULATIONS IN THE 5 TO 8 INCH RANGE. HAVE ISSUED A WINTER
STORM WARNING THROUGH NOON FOR THIS NARROW CORRIDOR INCLUDING LA
SALLE...KENDALL...GRUNDY...WILL...AND KANKAKEE COUNTIES. THE
WINTER WEATHER ADVISORY REMAINS IN EFFECT AFTER NOON FOR THE
COUNTIES THAT WERE UPGRADED TO A WINTER STORM WARNING.

MARSILI

&&

.AVIATION...

...POSSIBLE LAKE EFFECT SNOW SHOWERS THIS AFTERNOON THEN BLOWING
SNOW POSSIBLE THROUGH TONIGHT...

18Z TAFS...OVERALL...GOING FORECAST IN GOOD SHAPE WITH NO MAJOR
CHANGES. SFC LOW OVER EASTERN ILLINOIS WILL MOVE EAST ACROSS THE
OHIO VALLEY THIS AFTERNOON. BAND OF SNOW ON THE NORTH SIDE OF THIS
SYSTEM IS FINALLY MOVING EAST/SOUTHEAST. VIS RESTRICTIONS PARTLY
DUE TO FOG/MIST BUT SOME LIGHT SNOW/FLURRIES WILL CONTINUE FOR A
FEW MORE HRS.

ATTENTION SHIFTS TO LAKE EFFECT PLUME FORMING OVER CENTRAL LAKE
MICHIGAN. LATEST RADAR IMAGES SHOW THIS BAND BEGINNING TO SHIFT
SOUTHEAST. THIS BAND WILL CONTINUE TO SHIFT EAST THRU THE
AFTERNOON. NOT SURE IF IT WILL IMPACT ORD...BETTER CHANCE AT MDW
BUT SHORT DURATION IF IT DOES. PREVIOUS FORECAST HANDLED THIS
WITH A TEMPO AND THAT SEEMS REASONABLE TO CONTINUE AND CAN AMEND
TO REMOVE IF THE BAND SHIFTS EAST SOONER. THIS WILL LIKELY IMPACT
GYY THE MOST OF ALL THE TAFS AND HAVE CONTINUED WITH 1/2SM AND
MODERATE SNOW THRU LATE AFTERNOON.

WINDS HAVE SHIFTED NORTHERLY WITH GUSTS 20-25KTS OVER NORTHWEST
IL. STRONGEST WINDS WILL AFFECT AREAS ACROSS CENTRAL IL JUST
BEHIND THE SFC LOW. BUT EXPECT GUSTS 20-25KTS TO CONTINUE...ONCE
THEY DEVELOP...THRU THE EVENING HRS AND BEGIN TO RELAX TO 18-20KTS
OVERNIGHT. WINDS WILL GRADUALLY TURN NORTHWEST THIS EVENING AND
MORE WESTERLY THURSDAY MORNING. SNOW HAS BEEN VERY DRY AND FLUFFY
AND EVEN AT THESE WIND SPEEDS...EXPECT SOME BLOWING/DRIFTING SNOW
AND PREVAILING MVFR VISIBILITIES LOOK GOOD...THOUGH THEY COULD
OCCASIONALLY DROP LOWER...ESPECIALLY LATER THIS AFTERNOON AND THIS
EVENING.

CIGS GENERALLY MVFR BETWEEN 1-2KFT BUT THEY QUICKLY LIFT/SCATTER
ACROSS SOUTHWEST WI AND EASTERN IA. SOUNDINGS/RH FIELDS INDICATE
POTENTIAL FOR CIGS IN THIS RANGE THROUGH THE LATE EVENING...THEN
SCATTERING OUT AFTER MIDNIGHT. DECIDED TO JUST LEAVING THE GOING
CIGS AS IS BUT THEY COULD SCATTER OUT SOONER OR LIFT HIGHER THAN
NEW FORECAST INDICATES. CMS

&&

.MARINE...
345 AM CST

LOW PRESSURE WILL MOVE FROM THE CENTRAL PLAINS ACROSS THE LOWER OHIO
VALLEY LATER TODAY...WITH WINDS SHIFTING TO THE NORTH AND NORTHWEST
AND INCREASING TO 30 TO 35 KNOTS ACROSS LAKE MICHIGAN THIS
AFTERNOON...WITH FRIGID ARCTIC AIR SPREADING ACROSS THE LAKE. THE
COMBINATION OF STRONG WINDS...HIGH WAVES AND BITTER COLD AIR
TEMPERATURES LEADING TO HEAVY FREEZING SPRAY. HAVE ISSUED HEADLINES
FOR GALES ON SOUTHERN LAKE MICHIGAN AS WELL AS HEAVY FREEZING SPRAY
WARNING FOR ENTIRE LAKE. WINDS WILL EASE BELOW GALE FORCE ON THE
SOUTH END OF THE LAKE LATE TONIGHT...THOUGH APPEARS A PERIOD OF
20-30 KNOT WINDS AND ENTRENCHED ARCTIC AIRMASS WILL CONTINUE PRODUCE
A FREEZING SPRAY THREAT THROUGH FRIDAY/SATURDAY. SOME MODERATION OF
TEMPERATURES EXPECTED BY SATURDAY AS WINDS BACK SOUTH IN ADVANCE OF
LOW PRESSURE EXPECTED TO MOVE ACROSS THE MIDWEST AT THAT TIME.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER STORM WARNING...ILZ019-ILZ020-ILZ021-ILZ022-ILZ023 UNTIL
     NOON WEDNESDAY.

     WINTER WEATHER ADVISORY...ILZ019-ILZ020-ILZ021-ILZ022-ILZ023
     UNTIL MIDNIGHT THURSDAY.

     WIND CHILL WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...MIDNIGHT THURSDAY TO NOON
     FRIDAY.

     WINTER STORM WARNING...ILZ014 UNTIL 4 PM WEDNESDAY.

     WINTER WEATHER ADVISORY...ILZ014...4 PM WEDNESDAY TO MIDNIGHT
     THURSDAY.

     WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012-ILZ013-ILZ032-ILZ033-ILZ039 UNTIL
     MIDNIGHT THURSDAY.

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-
     INZ019...MIDNIGHT THURSDAY TO NOON FRIDAY.

     WINTER STORM WARNING...INZ001 UNTIL 4 PM WEDNESDAY.

     WINTER WEATHER ADVISORY...INZ001...4 PM WEDNESDAY TO MIDNIGHT
     THURSDAY.

     WINTER STORM WARNING...INZ002 UNTIL MIDNIGHT THURSDAY.

     WINTER WEATHER ADVISORY...INZ010-INZ011-INZ019 UNTIL MIDNIGHT
     THURSDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
     LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3 PM WEDNESDAY TO 6 AM
     THURSDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
     LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
     LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3
     PM WEDNESDAY TO 6 AM SATURDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ740-LMZ741-LMZ742-LMZ743...4
     PM WEDNESDAY TO 10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...4 PM
     WEDNESDAY TO 10 AM THURSDAY.

     GALE WARNING...LMZ744-LMZ745...4 PM WEDNESDAY TO 6 AM THURSDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ744-LMZ745...4 PM WEDNESDAY TO
     NOON THURSDAY.

&&

$$


000
FXUS63 KILX 141645
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1045 AM CST WED JAN 14 2009

.DISCUSSION...
ISSUED 1045 AM CST WED JAN 14 2009

UPDATED THE FORECAST LATE THIS MORNING TO ADJUST LIGHT SNOW
CHANCES TODAY AND FALLING TEMPERATURES. ALSO INCREASE WINDS A BIT
SOONER AND HAVE BLOWING SNOW LATE THIS MORNING WEST OF HIGHWAY 51
FROM BLOOMINGTON TO DECATUR AND THIS AFTERNOON EAST OF HERE.

15Z/10 AM SURFACE MAP SHOWS 1011 MB LOW PRESSURE OVER CENTRAL IL
JUST NE OF LINCOLN. COLD FRONT HAS PRESSED JUST EAST OF I-55 WITH
INCREASING NNW WINDS BEHIND THE COLD FRONT OF 15 TO 25 MPH AND
GUSTS OF 25 TO 40 MPH. TEMPERATURES ALSO FALLING BEHIND THE COLD
FRONT WITH GALESBURG AND MACOMB DOWN TO 10F. IN WARM SECTOR MILDER
TEMPERATURES ARE IN THE LOWER 30S FROM DECATUR AND TAYLORVILLE
AND ROBINSON SOUTH. LIGHT SHOW SHOWERS CONTINUE NORTH OF I-70 AND
ESPECIALLY NE OF I-74 BETWEEN BLOOMINGTON AND CHAMPAIGN WHERE UP
TO AN ADDITIONAL 1 INCH OF SNOW POSSIBLE BEFORE DIMINISHING TO
FLURRIES IN THE NEXT FEW HOURS. THE I-74 CORRIDOR OVER IL RECEIVED
HEAVIEST SNOWFALL OF 4 TO 6 INCHES SINCE LATE TUESDAY EVENING.

SHORT RANGE MODELS SIMILAR IN TAKING LOW PRESSURE AND WEAKENING TO
1015 MB AS IT MOVES QUICKLY EAST TO NEAR HUNTINGTON ON THE
KY/OH/WV BORDER BY 00Z/6 PM WHILE 1045 MB ARCTIC HIGH PRESSURE
OVER SASKATCHEWAN BUILDING INTO THE CENTRAL PLAINS. THIS TO DRIVE
IN THE COLDEST AIR OF THE SEASON INTO THE MIDWEST THROUGH FRI MORNING.
INCREASING NW WINDS WILL DRIVE WIND CHILLS DOWN TO 15 TO 25 BELOW
ZERO TONIGHT. KEPT WINTER WEATHER ADVISORY NORTH OF I-70 GOING
TODAY.



HUETTL

&&

.AVIATION...
ISSUED 525 AM CST WED JAN 14 2009

LOW PRESSURE OVER NE MISSOURI IS EXPECTED TO PASS JUST NORTH OF
SPI OVER THE NEXT SEVERAL HOURS BASED ON 3 HOURLY PRESSURE FALLS.
ON THE BACKSIDE OF THE STORM...3 HOURLY PRESSURE RISES OF 8-9 MB
INDICATING SOME STRONG WINDS PUSHING IN LATER THIS MRNG ACRS THE
WEST...AND OVR THE REMAINDER OF THE AREA THIS AFTN. AREAS THAT
RECEIVED THE SNOWFALL...FROM 2 TO 5 INCHES...MAINLY NORTH OF I-72
WL SEE SOME BLOWING AND DRIFTING OF THE POWDERY SNOW THAT WL
REDUCE VSBYS TO 1 TO 3 MILES...AND IN SOME AREAS DOWN TO ONE HALF
MILE. THE BULK OF THE STEADIER SNOWS WL SHIFT EAST OF THE AREA
OVR THE NEXT SVL HOURS...HOWEVER...AS THE STORM SHIFTS INTO ERN
IL LATER THIS MRNG...ANOTHER BAND OF SNOW SHOWERS WILL MOVE ACRS
THE AREA WITH THE COLD FRONT. THE MAIN THREAT FOR BLOWING SNOW
WL BE JUST AFTR FROPA LATE THIS MRNG WEST AND ACRS THE EAST EARLY
THIS AFTN...AND WL LAST INTO EARLY THIS EVENING WITH WINDS GRDLY
DIMINISHING AFTR 02Z. THE MVFR CIGS AND VSBYS...WITH LOCALLY IFR
AND LIFR CONDITIONS IN SNOW AND BLOWING SNOW WL IMPROVE TO VFR
CONDITIONS AT ALL FORECAST SITES AFTR 00Z.

SMITH

&&

.PREV DISCUSSION...
ISSUED 235 AM CST WED JAN 14 2009

LATEST SURFACE MAP SHOWED CENTER OF CLIPPER SYSTEM ACROSS SOUTHWEST
IOWA. SNOW HAS BEEN RAPIDLY MOVING ACROSS THE CWA OVERNIGHT...WITH
THE CORE OF THE HEAVIER SNOWS GENERALLY ADVANCING EAST-SOUTHEAST
FROM A GALESBURG TO PEORIA LINE. HOWEVER...REGIONAL MOSAICS
ALREADY SHOWING THE BACK EDGE OF THE SNOW SHIELD APPROACHING WEST
CENTRAL ILLINOIS. TEMPERATURES ACROSS THE AREA HAVE BEEN RISING
OVER THE LAST SEVERAL HOURS AND HAD REACHED INTO THE LOWER 20S
AROUND JACKSONVILLE.

SHORT TERM CONCERNS WITH THE FORECAST INVOLVE THE ENDING OF THE
SNOW AND SUBSEQUENT ISSUES WITH BLOWING SNOW...FOLLOWED BY THE
BITTER COLD WEATHER THE NEXT FEW DAYS.

SHORT TERM...TODAY THROUGH FRIDAY...
LATEST RUC MODEL TAKES SURFACE LOW ACROSS THE CENTER OF THE CWA
BETWEEN 12-18Z THIS MORNING. HEAVIEST STORM TOTAL SNOWS OF AROUND
3-5 INCHES EXPECTED ROUGHLY ALONG THE I-74 CORRIDOR...WITH SOME
LOCALLY HIGHER AMOUNTS. EXPANDED THE WINTER WEATHER ADVISORY
FURTHER SOUTH TO INCLUDE AREAS DOWN TO AROUND I-70...WHERE THE
TRAJECTORY OF THE HEAVIER SNOW BANDS MAY CAUSE SOME PROBLEMS.
HOWEVER...OVERALL SOUTHERN EDGE OF THE SNOW ACCUMULATIONS SHOULD
BE FAIRLY SHARP. WINDS STILL EXPECTED TO REALLY PICK UP LATE
MORNING AND INTO THE AFTERNOON IN TIGHT PRESSURE GRADIENT BEHIND
THE DEPARTING HIGH. WITH THIS SNOW BEING RATHER FLUFFY -- SNOW TO
WATER RATIOS PROBABLY ALONG THE ORDER OF 15-20 TO 1 -- EXPECTING
BLOWING SNOW ISSUES TO DEVELOP. THIS SHOULD BEGIN TO TAPER OFF A
BIT DURING THE EVENING.

NEXT ORDER OF BUSINESS IS WITH WIND CHILL HEADLINES. WIND SPEEDS
EXPECTED TO REMAIN IN THE TEENS THROUGH THE NIGHT AS THE ARCTIC
AIRMASS INVADES THE AREA. WITH THE FRESH SNOW COVER...WENT CLOSE
TO THE COLDER NAM MOS GUIDANCE FOR TEMPERATURES...WHICH BRINGS
LOWS OF -10F OR COLDER ACROSS THE NORTHERN CWA TONIGHT AND ZERO
DEGREES ALL THE WAY DOWN TO I-70. WIND CHILLS ACROSS THE NORTHERN
HALF OF THE CWA EXPECTED TO EASILY REACH WARNING CRITERIA OF -25F
FROM ABOUT MIDNIGHT TONIGHT THROUGH NOON THURSDAY...AND WILL BE
CLOSE THURSDAY NIGHT WITH THE CORE OF THE ARCTIC HIGH JUST TO OUR
WEST. IN ORDER TO SIMPLIFY THINGS...ELECTED TO HAVE A WIND CHILL
WARNING RUNNING FROM 6 PM TONIGHT THROUGH NOON FRIDAY...AS AN
UPGRADE OF THE ORIGINAL ADVISORY IN THIS AREA. HOWEVER...THE
WARNING MAY LATER NEED TO BE DOWNGRADED THURSDAY AFTERNOON.
FURTHER SOUTH...EXPANDED THE WIND CHILL ADVISORY TO COVER THE
REMAINDER OF THE CWA...ALTHOUGH AREAS SOUTH OF I-70 WILL BE
BORDERLINE.

DEPARTURE OF HIGH PRESSURE ON FRIDAY WILL LEAD TO WARM AIR
ADVECTION...WITH AFTERNOON TEMPERATURES RECOVERING INTO THE TEENS
AFTER A BRUTAL START IN THE TEENS BELOW IN SOME AREAS.

LONG TERM...FRIDAY NIGHT THROUGH SUNDAY...

NOT MUCH CHANGE MADE TO THIS PORTION OF THE FORECAST...DUE TO
CONCENTRATION ON THE SHORT TERM PROBLEMS. NAM AND GFS HINTING AT
WAA PRECIPITATION DEVELOPMENT FRIDAY AFTERNOON AND
EVENING...MAINLY TO OUR WEST. BETTER PRECIPITATION CHANCES TO
ACCOMPANY NEXT CLIPPER SYSTEM WHICH WILL ZIP ACROSS THE AREA ON
SATURDAY. MODELS KEEPING MUCH OF THIS PRECIPITATION TO OUR NORTH
AT THIS TIME.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 12 PM CST FRIDAY
FOR ILZ049>057-061>063-066>068-071>073.

WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR
ILZ027>031-036>038-040>057-061.

WIND CHILL WARNING FROM 6 PM THIS EVENING TO 12 PM CST FRIDAY
FOR ILZ027>031-036>038-040>048.

&&

$$


000
FXUS63 KLOT 141534
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
934 AM CST WED JAN 14 2009

.DISCUSSION...
934 AM CST

HAVE EXPANDED THE WINTER STORM WARNING EASTWARD ACROSS THE I-80
CORRIDOR AS THE HEAVIEST BAND HAS SET UP ACROSS THE STRETCH AND
WILL LIKELY CONTINUE THROUGH THE REST OF THE MORNING AS THE SFC
LOW TRACKS FROM WEST CENTRAL ILLINOIS EASTWARD ACROSS THE STATE.
SNOW RATIOS ARE VERY HIGH AT ABOUT 25 TO 1...SO WHILE THERE IS
LITTLE QPF INVOLVED...SNOW AMOUNTS WILL BE INTO WARNING CRITERIA
OF AROUND 6 TO 8 INCHES WITH SOME LOCALLY HIGHER AMOUNTS POSSIBLE
IN THE WARNED COUNTIES. KEPT PORTER COUNTY IN THROUGH MIDNIGHT AS
IT APPEARS THAT LAKE EFFECT SNOW WILL CONTINUE AFTER THE SYSTEM
PASSES. WILL HAVE TO FURTHER ASSESS THE LAKE EFFECT SITUATION THIS
AFTERNOON AS SOME OF THE GUIDANCE HAS BEEN SPINNING UP A SFC LOW
AND PROPAGATING IT DOWN THE LAKE. IF THIS LOW WOBBLES FURTHER
WEST...MAY NEED TO RE-EXPAND THE WARNING BACK INTO LAKE COUNTY.
ALSO AM KEEPING TABS ON SOME LAKE EFFECT SNOW SHOWERS UP IN
SOUTHEAST WISCONSIN THAT MAY TURN SOUTH ACROSS LAKE COUNTY
ILLINOIS.

CONDITIONS WILL GRADUALLY IMPROVE FROM NORTHWEST TO SOUTHEAST THIS
MORNING WITH THE BACK EDGE OF THE SNOW ALREADY ACROSS NORTHWEST
ILLINOIS.

HALBACH

&&

.PREV DISCUSSION...
720 AM CST

A FOCUSED FRONTOGENETIC BAND...COMBINED WITH MORE FAVORABLE
DENDRITIC SNOW GROWTH HAS LED SNOW ACCUMULATIONS AROUND 5 INCHES
THROUGH 630 AM...IN A NARROW AXIS ROUGHLY ALONG THE INTERSTATE 80
CORRIDOR IN NORTH CENTRAL ILLINOIS FROM NORTHERN LA SALLE THROUGH
GRUNDY AND KENDALL COUNTIES. THE BACK EDGE OF THE SNOW IS STILL
BACK ACROSS THE MISSISSIPPI RIVER. SNOW RATES SHOULD BEGIN TO
TAPER OFF SOMEWHAT AS ISENTROPIC UPGLIDE BEGINS TO WEAKEN THIS
MORNING...BUT WITH FRONTOGENETIC FORCING PERSISTING THROUGH MID
MORNING MAY SEE AN ADDITIONAL 1 TO 3 INCHES OF ACCUMULATION ALONG
INTERSTATE 80 CORRIDOR IN NORTHEAST ILLINOIS BRINGING STORM TOTAL
SNOW ACCUMULATIONS IN THE 5 TO 8 INCH RANGE. HAVE ISSUED A WINTER
STORM WARNING THROUGH NOON FOR THIS NARROW CORRIDOR INCLUDING LA
SALLE...KENDALL...GRUNDY...WILL...AND KANKAKEE COUNTIES. THE
WINTER WEATHER ADVISORY REMAINS IN EFFECT AFTER NOON FOR THE
COUNTIES THAT WERE UPGRADED TO A WINTER STORM WARNING.

MARSILI

&&

.AVIATION...

545 AM CST

1200 UTC TAFS...MAIN FOCUS OF TERMINAL FORECASTS THIS MORNING
OBVIOUSLY WITH ALBERTA CLIPPER MOVING ACROSS THE MIDWEST AND
RESULTING VIS/CIG ISSUES ASSOCIATED WITH SNOW.

MORNING VAPOR/PROFILER DATA INDICATES SHORT WAVE TROUGH MOVING
ACROSS WESTERN IA...WITH SURFACE LOW OVER NORTHEAST MO AT 10Z.
SHORT TERM GUIDANCE IN EXCELLENT AGREEMENT IN TAKING THIS SYSTEM
QUICKLY ACROSS CENTRAL ILLINOIS THROUGH MIDDAY. ANOTHER WEAKER MID
LEVEL DISTURBANCE OVER NORTHERN MINNESOTA EXPECTED TO SLIDE ACROSS
WI INTO THIS AFTERNOON. BEST FORCING OCCURS WITH CLIPPER THROUGH
THE EARLY/MID MORNING HOURS...WITH REGIONAL RADAR INDICATING
HEAVIEST SNOW BAND FROM VICINITY KMLI TO KARR. RADAR TRENDS
SUGGEST THAT KORD AND KRFD WILL REMAIN JUST NORTH OF THE HEAVIEST
BAND...WHILE KMDW/KGYY EXPECTED TO EXPERIENCE SLIGHTLY LOWER
CIG/VIS CONDITIONS THIS MORNING WITH POTENTIAL FOR MODERATE SNOW.
EXPECT VSBYS WILL BEGIN TO IMPROVE FROM THE WEST BY MID/LATE
MORNING AS SYSTEM PASSES BY TO THE SOUTH. HOWEVER...AS LOW LEVEL
WINDS BACK TO NORTHEAST/NORTH LATER THIS MORNING AND EARLY
AFTERNOON WILL SEE POTENTIAL FOR SOME LAKE EFFECT SNOW IMPINGING
UPON CHICAGO TERMINALS...WITH 06Z RUN OF WRF EVEN INDICATING
MESOSCALE CIRCULATION DEVELOPING WITH DELTA/T APPROACHING 20 DEG.
EXPECT LAKE EFFECT TO LINGER ACROSS KGYY INTO EARLY THIS EVENING.

WINDS THEN SHIFT NORTHWEST LATER IN AFTERNOON AND INCREASE WITH
GUSTS INTO MID 20 KNOT RANGE EXPECTED TO LEAD TO BLOWING OF
NEW POWDERY SNOWFALL. HAVE HELD VSBYS IN MVFR RANGE INTO THIS
EVENING WITH STRONGEST WINDS...THEN EXPECT GRADUAL DECREASE IN
WINDS AND IMPROVEMENT IN VISIBILITY OVERNIGHT.

RATZER

&&

.MARINE...
345 AM CST

LOW PRESSURE WILL MOVE FROM THE CENTRAL PLAINS ACROSS THE LOWER OHIO
VALLEY LATER TODAY...WITH WINDS SHIFTING TO THE NORTH AND NORTHWEST
AND INCREASING TO 30 TO 35 KNOTS ACROSS LAKE MICHIGAN THIS
AFTERNOON...WITH FRIGID ARCTIC AIR SPREADING ACROSS THE LAKE. THE
COMBINATION OF STRONG WINDS...HIGH WAVES AND BITTER COLD AIR
TEMPERATURES LEADING TO HEAVY FREEZING SPRAY. HAVE ISSUED HEADLINES
FOR GALES ON SOUTHERN LAKE MICHIGAN AS WELL AS HEAVY FREEZING SPRAY
WARNING FOR ENTIRE LAKE. WINDS WILL EASE BELOW GALE FORCE ON THE
SOUTH END OF THE LAKE LATE TONIGHT...THOUGH APPEARS A PERIOD OF
20-30 KNOT WINDS AND ENTRENCHED ARCTIC AIRMASS WILL CONTINUE PRODUCE
A FREEZING SPRAY THREAT THROUGH FRIDAY/SATURDAY. SOME MODERATION OF
TEMPERATURES EXPECTED BY SATURDAY AS WINDS BACK SOUTH IN ADVANCE OF
LOW PRESSURE EXPECTED TO MOVE ACROSS THE MIDWEST AT THAT TIME.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER STORM WARNING...ILZ019-ILZ020-ILZ021-ILZ022-ILZ023 UNTIL
     NOON WEDNESDAY.

     WINTER WEATHER ADVISORY...ILZ019-ILZ020-ILZ021-ILZ022-ILZ023
     UNTIL MIDNIGHT THURSDAY.

     WIND CHILL WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...MIDNIGHT THURSDAY TO NOON
     FRIDAY.

     WINTER STORM WARNING...ILZ014 UNTIL 4 PM WEDNESDAY.

     WINTER WEATHER ADVISORY...ILZ014...4 PM WEDNESDAY TO MIDNIGHT
     THURSDAY.

     WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012-ILZ013-ILZ032-ILZ033-ILZ039 UNTIL
     MIDNIGHT THURSDAY.

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-
     INZ019...MIDNIGHT THURSDAY TO NOON FRIDAY.

     WINTER STORM WARNING...INZ001 UNTIL 4 PM WEDNESDAY.

     WINTER WEATHER ADVISORY...INZ001...4 PM WEDNESDAY TO MIDNIGHT
     THURSDAY.

     WINTER STORM WARNING...INZ002 UNTIL MIDNIGHT THURSDAY.

     WINTER WEATHER ADVISORY...INZ010-INZ011-INZ019 UNTIL MIDNIGHT
     THURSDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
     LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3 PM WEDNESDAY TO 6 AM
     THURSDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
     LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
     LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3
     PM WEDNESDAY TO 6 AM SATURDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ740-LMZ741-LMZ742-LMZ743...4
     PM WEDNESDAY TO 10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...4 PM
     WEDNESDAY TO 10 AM THURSDAY.

     GALE WARNING...LMZ744-LMZ745...4 PM WEDNESDAY TO 6 AM THURSDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ744-LMZ745...4 PM WEDNESDAY TO
     NOON THURSDAY.

&&

$$


000
FXUS63 KLOT 141339
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
739 AM CST WED JAN 14 2009

.DISCUSSION...
720 AM CST

A FOCUSED FRONTOGENETIC BAND...COMBINED WITH MORE FAVORABLE
DENDRITIC SNOW GROWTH HAS LED SNOW ACCUMULATIONS AROUND 5 INCHES
THROUGH 630 AM...IN A NARROW AXIS ROUGHLY ALONG THE INTERSTATE 80
CORRIDOR IN NORTH CENTRAL ILLINOIS FROM NORTHERN LA SALLE THROUGH
GRUNDY AND KENDALL COUNTIES. THE BACK EDGE OF THE SNOW IS STILL
BACK ACROSS THE MISSISSIPPI RIVER. SNOW RATES SHOULD BEGIN TO
TAPER OFF SOMEWHAT AS ISENTROPIC UPGLIDE BEGINS TO WEAKEN THIS
MORNING...BUT WITH FRONTOGENETIC FORCING PERSISTING THROUGH MID
MORNING MAY SEE AN ADDITIONAL 1 TO 3 INCHES OF ACCUMULATION ALONG
INTERSTATE 80 CORRIDOR IN NORTHEAST ILLINOIS BRINGING STORM TOTAL
SNOW ACCUMULATIONS IN THE 5 TO 8 INCH RANGE. HAVE ISSUED A WINTER
STORM WARNING THROUGH NOON FOR THIS NARROW CORRIDOR INCLUDING LA
SALLE...KENDALL...GRUNDY...WILL...AND KANKAKEE COUNTIES. THE
WINTER WEATHER ADVISORY REMAINS IN EFFECT AFTER NOON FOR THE
COUNTIES THAT WERE UPGRADED TO A WINTER STORM WARNING.

MARSILI

&&

.PREV DISCUSSION...
400 AM CST

FORECAST CONCERNS WILL CENTER ON ACCUMULATING SNOW TODAY...POTENTIAL
OF BLOWING THIS AFTERNOON/EVENING...FOLLOWED BY BITTERLY COLD
TEMPERATURES AND EXTREME WIND CHILLS. WINTER WEATHER ADVISORY FOR
SNOW AND BLOWING SNOW WILL REMAIN IN EFFECT FOR ALL OF THE FORECAST
AREA THROUGH THIS EVENING...AND A WIND CHILL WARNING HAS BEEN ISSUED
FOR ALL OF THE FORECAST AREA FROM MIDNIGHT TONIGHT THROUGH FRIDAY
MORNING.

AT 09Z...SURFACE LOW IS POSITIONED ACROSS SOUTH CENTRAL IOWA WITH
STRONGEST SFC PRESSURE FALLS CENTERED ACROSS WEST CENTRAL ILLINOIS
JUST TO THE SOUTH OF PEORIA. AS THIS LOW CONTINUES INTO WEST
CENTRAL ILLINOIS EARLY THIS MORNING...ZONE OF STRONGEST ISENTROPIC
ASCENT WILL SHIFT ACROSS SOUTHERN PORTIONS OF THE FORECAST AREA
OVER THE NEXT FEW HOURS. TIME/HEIGHT SECTIONS ALSO INDICATE MORE
FAVORABLE UVM BECOMING BASED IN PROGRESSIVELY LOWER LEVELS...IN
BETTER PROXIMITY TO DENDRITIC GROWTH ZONE. THUS...MOST EFFICIENT
SNOW ACCUMULATION PERIOD IS ANTICIPATED IN THE 12Z-15Z TIME FRAME
THIS MORNING. PLACEMENT OF STRONGEST ISENTROPIC ASCENT STILL
FAVORS HEAVIEST SNOWFALL SOUTH OF INTERSTATE 80 WHERE 3 TO 5
INCHES WILL BE POSSIBLE BEFORE TAPERS OFF FROM WEST TO EAST FROM
MID MORNING THROUGH EARLY AFTERNOON. A FEW REPORTS ACROSS EAST
CENTRAL IOWA INDICATE A FEW LOCATIONS EVEN APPROACHING 6 INCHES
BUT FEEL THAT THESE AMOUNTS WILL BE HARDER TO ATTAIN DUE TO
ISENTROPIC ASCENT LIKELY BEING A BIT STRONGER ACROSS EASTERN IOWA.
FOR THIS AFTERNOON...WILL MAINTAIN HIGHER POPS FOR CONTINUED SNOW
ACROSS MAINLY NWRN INDIANA WITH LOW LEVEL THERMAL RIDGE/WAA
CONTINUING THROUGH EARLY AFTERNOON BEFORE SHIFTING EASTWARD. LAKE
EFFECT SNOW POTENTIAL WILL INCREASE THIS AFTERNOON AS COLDER AIR
DROPS INTO THE WESTERN GREAT LAKES BEHIND THIS STORM. MODIFICATION
OF NAM BUFKIT SOUNDINGS STILL SUPPORT AROUND 500 J/KG OF LAKE
INDUCED CAPE WITH LAKE INDUCED EQUIL LEVELS INCREASING TO AROUND
10K FT. THERMALLY INDUCED CONVERGENCE ALSO EXPECTED TO ENHANCE
LAKE EFFECT SNOW POTENTIAL...ESPECIALLY BY EVENING. THE LIMITING
FACTOR FOR LAKE EFFECT SNOW POTENTIAL TODAY IS DURATION OF
FAVORABLE FETCH DUE TO PROGRESSIVE NATURE OF SOUTHEASTWARD MOVING
1045 MB HIGH INTO THE NORTHERN PLAINS TONIGHT. THIS SHOULD BACK
THE WINDS ENOUGH TO KEEP THE REAL HEAVY LAKE EFFECT SNOW ACCUMS
MORE UP THE SHORELINE INTO FAR SOUTHWEST LOWER MICHIGAN.
NONETHELESS...WHEN ADDING THE SYNOPTIC SNOW ACCUM WITH THE LAKE
EFFECT SNOW...STORM TOTAL SNOW ACCUMULATIONS ACROSS PORTIONS OF
LAKE AND PORTER COUNTIES IN NORTHWEST MAY APPROACH 6 INCHES.
OTHER CONCERN TODAY WILL BE POTENTIAL OF BLOWING SNOW AND REDUCED
VISIBILITIES. MODELS HAVE BACKED OFF A BIT ON THE MAGNITUDE OF
WIND SPEEDS...ALTHOUGH STILL HAVE LINGERING CONCERN ACROSS
SOUTHERN PORTIONS OF THE CWA WHERE BRUNT OF ISALLOBARIC PUSH IS
ANTICIPATED. ACROSS THE FAR SOUTH WIND GUSTS COULD STILL REACH
INTO THE 30 TO 35 MPH RANGE TODAY WHICH WOULD RESULT IN SOME
SIGNIFICANT BLOWING AND DRIFTING CONCERNS WITH THE NEW SNOWFALL.
ELSEWHERE...EXPECTING GUSTS GENERALLY IN THE 25 TO 30 MPH RANGE
WHICH WILL LIKELY LEAD TO BLOWING SNOW AND REDUCED
VISIBILITIES...ESPECIALLY ACROSS RURAL MORE OPEN AREAS.

SKIES WILL CLEAR FROM WEST TO EAST THIS EVENING AS MUCH DRIER
BITTERLY COLD ARCTIC AIR CONTINUES TO ADVECT SOUTHWARD...AND WIND
CHILLS OF 30 BELOW TO 40 BELOW ARE EXPECTED AFTER MIDNIGHT WITH AIR
TEMPERATURES RANGING FROM AROUND 15 BELOW FAR NORTH TO 5 TO 10 BELOW
FAR SOUTH. CURRENT FORECASTED WIND CHILLS ACROSS FAR SOUTHERN CWA
REACH AS COLD AS 30 BELOW...SO EXPECTING WIND CHILLS TO REACH
WARNING CRITERIA ACROSS MOST OR ALL OF THE CWA. WIND CHILLS MAY MOVE
BACK INTO ADVISORY RANGE DURING THE DAY THURSDAY...BUT WITH ARCTIC
HIGH APPROACHING SEE LITTLE CHANCE OF TEMPERATURE RECOVERY DURING
THE DAY. COLDEST NIGHT APPEARS TO BE THURSDAY NIGHT WITH AIR
TEMPERATURES DROPPING TO AROUND 20 BELOW NORTH CENTRAL ILLINOIS TO
10 TO 20 BELOW SOUTHERN AREAS. WIND CHILL WARNING CRITERIA WILL
LIKELY EASILY BE MET THURSDAY NIGHT. BASED ON TWO SUCCESSIVE NIGHTS
OF MEETING WIND CHILL WARNING CRITERIA...HAVE OPTED TO ISSUE A WIND
CHILL WARNING FROM AFTER MIDNIGHT TONIGHT THROUGH FRIDAY MORNING.
BITTER COLD TEMPERATURES WILL PERSIST THROUGH THE FIRST PART OF THE
WEEKEND...AND MODELS DIVERGE SOMEWHAT ON TRACK OF NEXT CLIPPER
SYSTEM WITH THE GFS A NORTHERN OUTLIER. FOR THIS FORECAST HAVE
TRENDED TO ECMWF/NAM CONSENSUS OF SFC LOW TRACKING INTO IOWA LATE
FRIDAY NIGHT WITH ANOTHER CHANCE OF AN OVERRUNNING EVENT. STILL MUCH
UNCERTAINTY REGARDING TRACK OF THIS SYSTEM...SO WILL JUST KEEP
CHANCE POPS FOR SNOW FOR FRIDAY NIGHT/SATURDAY. WITH FOCUS ON SHORT
TERM...HAVE MADE FEW CHANGES TO EXTENDED GRIDS.

MARSILI

&&

.AVIATION...

545 AM CST

1200 UTC TAFS...MAIN FOCUS OF TERMINAL FORECASTS THIS MORNING
OBVIOUSLY WITH ALBERTA CLIPPER MOVING ACROSS THE MIDWEST AND
RESULTING VIS/CIG ISSUES ASSOCIATED WITH SNOW.

MORNING VAPOR/PROFILER DATA INDICATES SHORT WAVE TROUGH MOVING
ACROSS WESTERN IA...WITH SURFACE LOW OVER NORTHEAST MO AT 10Z.
SHORT TERM GUIDANCE IN EXCELLENT AGREEMENT IN TAKING THIS SYSTEM
QUICKLY ACROSS CENTRAL ILLINOIS THROUGH MIDDAY. ANOTHER WEAKER MID
LEVEL DISTURBANCE OVER NORTHERN MINNESOTA EXPECTED TO SLIDE ACROSS
WI INTO THIS AFTERNOON. BEST FORCING OCCURS WITH CLIPPER THROUGH
THE EARLY/MID MORNING HOURS...WITH REGIONAL RADAR INDICATING
HEAVIEST SNOW BAND FROM VICINITY KMLI TO KARR. RADAR TRENDS
SUGGEST THAT KORD AND KRFD WILL REMAIN JUST NORTH OF THE HEAVIEST
BAND...WHILE KMDW/KGYY EXPECTED TO EXPERIENCE SLIGHTLY LOWER
CIG/VIS CONDITIONS THIS MORNING WITH POTENTIAL FOR MODERATE SNOW.
EXPECT VSBYS WILL BEGIN TO IMPROVE FROM THE WEST BY MID/LATE
MORNING AS SYSTEM PASSES BY TO THE SOUTH. HOWEVER...AS LOW LEVEL
WINDS BACK TO NORTHEAST/NORTH LATER THIS MORNING AND EARLY
AFTERNOON WILL SEE POTENTIAL FOR SOME LAKE EFFECT SNOW IMPINGING
UPON CHICAGO TERMINALS...WITH 06Z RUN OF WRF EVEN INDICATING
MESOSCALE CIRCULATION DEVELOPING WITH DELTA/T APPROACHING 20 DEG.
EXPECT LAKE EFFECT TO LINGER ACROSS KGYY INTO EARLY THIS EVENING.

WINDS THEN SHIFT NORTHWEST LATER IN AFTERNOON AND INCREASE WITH
GUSTS INTO MID 20 KNOT RANGE EXPECTED TO LEAD TO BLOWING OF
NEW POWDERY SNOWFALL. HAVE HELD VSBYS IN MVFR RANGE INTO THIS
EVENING WITH STRONGEST WINDS...THEN EXPECT GRADUAL DECREASE IN
WINDS AND IMPROVEMENT IN VISIBILITY OVERNIGHT.

RATZER

&&

.MARINE...
345 AM CST

LOW PRESSURE WILL MOVE FROM THE CENTRAL PLAINS ACROSS THE LOWER OHIO
VALLEY LATER TODAY...WITH WINDS SHIFTING TO THE NORTH AND NORTHWEST
AND INCREASING TO 30 TO 35 KNOTS ACROSS LAKE MICHIGAN THIS
AFTERNOON...WITH FRIGID ARCTIC AIR SPREADING ACROSS THE LAKE. THE
COMBINATION OF STRONG WINDS...HIGH WAVES AND BITTER COLD AIR
TEMPERATURES LEADING TO HEAVY FREEZING SPRAY. HAVE ISSUED HEADLINES
FOR GALES ON SOUTHERN LAKE MICHIGAN AS WELL AS HEAVY FREEZING SPRAY
WARNING FOR ENTIRE LAKE. WINDS WILL EASE BELOW GALE FORCE ON THE
SOUTH END OF THE LAKE LATE TONIGHT...THOUGH APPEARS A PERIOD OF
20-30 KNOT WINDS AND ENTRENCHED ARCTIC AIRMASS WILL CONTINUE PRODUCE
A FREEZING SPRAY THREAT THROUGH FRIDAY/SATURDAY. SOME MODERATION OF
TEMPERATURES EXPECTED BY SATURDAY AS WINDS BACK SOUTH IN ADVANCE OF
LOW PRESSURE EXPECTED TO MOVE ACROSS THE MIDWEST AT THAT TIME.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER STORM WARNING...ILZ019-ILZ020-ILZ021-ILZ022-ILZ023 UNTIL
     NOON WEDNESDAY.

     WINTER WEATHER ADVISORY...ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023...NOON WEDNESDAY TO MIDNIGHT THURSDAY.

     WIND CHILL WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...MIDNIGHT THURSDAY TO NOON
     FRIDAY.

     WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012-ILZ013-ILZ014-ILZ032-ILZ033-ILZ039
     UNTIL MIDNIGHT THURSDAY.

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-
     INZ019...MIDNIGHT THURSDAY TO NOON FRIDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019
     UNTIL MIDNIGHT THURSDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
     LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3 PM WEDNESDAY TO 6 AM
     THURSDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
     LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
     LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3
     PM WEDNESDAY TO 6 AM SATURDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ740-LMZ741-LMZ742-LMZ743...4
     PM WEDNESDAY TO 10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...4 PM
     WEDNESDAY TO 10 AM THURSDAY.

     GALE WARNING...LMZ744-LMZ745...4 PM WEDNESDAY TO 6 AM THURSDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ744-LMZ745...4 PM WEDNESDAY TO
     NOON THURSDAY.

&&

$$


000
FXUS63 KLOT 141145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
545 AM CST WED JAN 14 2009

.DISCUSSION...
400 AM CST

FORECAST CONCERNS WILL CENTER ON ACCUMULATING SNOW TODAY...POTENTIAL
OF BLOWING THIS AFTERNOON/EVENING...FOLLOWED BY BITTERLY COLD
TEMPERATURES AND EXTREME WIND CHILLS. WINTER WEATHER ADVISORY FOR
SNOW AND BLOWING SNOW WILL REMAIN IN EFFECT FOR ALL OF THE FORECAST
AREA THROUGH THIS EVENING...AND A WIND CHILL WARNING HAS BEEN ISSUED
FOR ALL OF THE FORECAST AREA FROM MIDNIGHT TONIGHT THROUGH FRIDAY
MORNING.

AT 09Z...SURFACE LOW IS POSITIONED ACROSS SOUTH CENTRAL IOWA WITH
STRONGEST SFC PRESSURE FALLS CENTERED ACROSS WEST CENTRAL ILLINOIS
JUST TO THE SOUTH OF PEORIA. AS THIS LOW CONTINUES INTO WEST
CENTRAL ILLINOIS EARLY THIS MORNING...ZONE OF STRONGEST ISENTROPIC
ASCENT WILL SHIFT ACROSS SOUTHERN PORTIONS OF THE FORECAST AREA
OVER THE NEXT FEW HOURS. TIME/HEIGHT SECTIONS ALSO INDICATE MORE
FAVORABLE UVM BECOMING BASED IN PROGRESSIVELY LOWER LEVELS...IN
BETTER PROXIMITY TO DENDRITIC GROWTH ZONE. THUS...MOST EFFICIENT
SNOW ACCUMULATION PERIOD IS ANTICIPATED IN THE 12Z-15Z TIME FRAME
THIS MORNING. PLACEMENT OF STRONGEST ISENTROPIC ASCENT STILL
FAVORS HEAVIEST SNOWFALL SOUTH OF INTERSTATE 80 WHERE 3 TO 5
INCHES WILL BE POSSIBLE BEFORE TAPERS OFF FROM WEST TO EAST FROM
MID MORNING THROUGH EARLY AFTERNOON. A FEW REPORTS ACROSS EAST
CENTRAL IOWA INDICATE A FEW LOCATIONS EVEN APPROACHING 6 INCHES
BUT FEEL THAT THESE AMOUNTS WILL BE HARDER TO ATTAIN DUE TO
ISENTROPIC ASCENT LIKELY BEING A BIT STRONGER ACROSS EASTERN IOWA.
FOR THIS AFTERNOON...WILL MAINTAIN HIGHER POPS FOR CONTINUED SNOW
ACROSS MAINLY NWRN INDIANA WITH LOW LEVEL THERMAL RIDGE/WAA
CONTINUING THROUGH EARLY AFTERNOON BEFORE SHIFTING EASTWARD. LAKE
EFFECT SNOW POTENTIAL WILL INCREASE THIS AFTERNOON AS COLDER AIR
DROPS INTO THE WESTERN GREAT LAKES BEHIND THIS STORM. MODIFICATION
OF NAM BUFKIT SOUNDINGS STILL SUPPORT AROUND 500 J/KG OF LAKE
INDUCED CAPE WITH LAKE INDUCED EQUIL LEVELS INCREASING TO AROUND
10K FT. THERMALLY INDUCED CONVERGENCE ALSO EXPECTED TO ENHANCE
LAKE EFFECT SNOW POTENTIAL...ESPECIALLY BY EVENING. THE LIMITING
FACTOR FOR LAKE EFFECT SNOW POTENTIAL TODAY IS DURATION OF
FAVORABLE FETCH DUE TO PROGRESSIVE NATURE OF SOUTHEASTWARD MOVING
1045 MB HIGH INTO THE NORTHERN PLAINS TONIGHT. THIS SHOULD BACK
THE WINDS ENOUGH TO KEEP THE REAL HEAVY LAKE EFFECT SNOW ACCUMS
MORE UP THE SHORELINE INTO FAR SOUTHWEST LOWER MICHIGAN.
NONETHELESS...WHEN ADDING THE SYNOPTIC SNOW ACCUM WITH THE LAKE
EFFECT SNOW...STORM TOTAL SNOW ACCUMULATIONS ACROSS PORTIONS OF
LAKE AND PORTER COUNTIES IN NORTHWEST MAY APPROACH 6 INCHES.
OTHER CONCERN TODAY WILL BE POTENTIAL OF BLOWING SNOW AND REDUCED
VISIBILITIES. MODELS HAVE BACKED OFF A BIT ON THE MAGNITUDE OF
WIND SPEEDS...ALTHOUGH STILL HAVE LINGERING CONCERN ACROSS
SOUTHERN PORTIONS OF THE CWA WHERE BRUNT OF ISALLOBARIC PUSH IS
ANTICIPATED. ACROSS THE FAR SOUTH WIND GUSTS COULD STILL REACH
INTO THE 30 TO 35 MPH RANGE TODAY WHICH WOULD RESULT IN SOME
SIGNIFICANT BLOWING AND DRIFTING CONCERNS WITH THE NEW SNOWFALL.
ELSEWHERE...EXPECTING GUSTS GENERALLY IN THE 25 TO 30 MPH RANGE
WHICH WILL LIKELY LEAD TO BLOWING SNOW AND REDUCED
VISIBILITIES...ESPECIALLY ACROSS RURAL MORE OPEN AREAS.

SKIES WILL CLEAR FROM WEST TO EAST THIS EVENING AS MUCH DRIER
BITTERLY COLD ARCTIC AIR CONTINUES TO ADVECT SOUTHWARD...AND WIND
CHILLS OF 30 BELOW TO 40 BELOW ARE EXPECTED AFTER MIDNIGHT WITH AIR
TEMPERATURES RANGING FROM AROUND 15 BELOW FAR NORTH TO 5 TO 10 BELOW
FAR SOUTH. CURRENT FORECASTED WIND CHILLS ACROSS FAR SOUTHERN CWA
REACH AS COLD AS 30 BELOW...SO EXPECTING WIND CHILLS TO REACH
WARNING CRITERIA ACROSS MOST OR ALL OF THE CWA. WIND CHILLS MAY MOVE
BACK INTO ADVISORY RANGE DURING THE DAY THURSDAY...BUT WITH ARCTIC
HIGH APPROACHING SEE LITTLE CHANCE OF TEMPERATURE RECOVERY DURING
THE DAY. COLDEST NIGHT APPEARS TO BE THURSDAY NIGHT WITH AIR
TEMPERATURES DROPPING TO AROUND 20 BELOW NORTH CENTRAL ILLINOIS TO
10 TO 20 BELOW SOUTHERN AREAS. WIND CHILL WARNING CRITERIA WILL
LIKELY EASILY BE MET THURSDAY NIGHT. BASED ON TWO SUCCESSIVE NIGHTS
OF MEETING WIND CHILL WARNING CRITERIA...HAVE OPTED TO ISSUE A WIND
CHILL WARNING FROM AFTER MIDNIGHT TONIGHT THROUGH FRIDAY MORNING.
BITTER COLD TEMPERATURES WILL PERSIST THROUGH THE FIRST PART OF THE
WEEKEND...AND MODELS DIVERGE SOMEWHAT ON TRACK OF NEXT CLIPPER
SYSTEM WITH THE GFS A NORTHERN OUTLIER. FOR THIS FORECAST HAVE
TRENDED TO ECMWF/NAM CONSENSUS OF SFC LOW TRACKING INTO IOWA LATE
FRIDAY NIGHT WITH ANOTHER CHANCE OF AN OVERRUNNING EVENT. STILL MUCH
UNCERTAINTY REGARDING TRACK OF THIS SYSTEM...SO WILL JUST KEEP
CHANCE POPS FOR SNOW FOR FRIDAY NIGHT/SATURDAY. WITH FOCUS ON SHORT
TERM...HAVE MADE FEW CHANGES TO EXTENDED GRIDS.

MARSILI

&&

.AVIATION...

545 AM CST

1200 UTC TAFS...MAIN FOCUS OF TERMINAL FORECASTS THIS MORNING
OBVIOUSLY WITH ALBERTA CLIPPER MOVING ACROSS THE MIDWEST AND
RESULTING VIS/CIG ISSUES ASSOCIATED WITH SNOW.

MORNING VAPOR/PROFILER DATA INDICATES SHORT WAVE TROUGH MOVING
ACROSS WESTERN IA...WITH SURFACE LOW OVER NORTHEAST MO AT 10Z.
SHORT TERM GUIDANCE IN EXCELLENT AGREEMENT IN TAKING THIS SYSTEM
QUICKLY ACROSS CENTRAL ILLINOIS THROUGH MIDDAY. ANOTHER WEAKER MID
LEVEL DISTURBANCE OVER NORTHERN MINNESOTA EXPECTED TO SLIDE ACROSS
WI INTO THIS AFTERNOON. BEST FORCING OCCURS WITH CLIPPER THROUGH
THE EARLY/MID MORNING HOURS...WITH REGIONAL RADAR INDICATING
HEAVIEST SNOW BAND FROM VICINITY KMLI TO KARR. RADAR TRENDS
SUGGEST THAT KORD AND KRFD WILL REMAIN JUST NORTH OF THE HEAVIEST
BAND...WHILE KMDW/KGYY EXPECTED TO EXPERIENCE SLIGHTLY LOWER
CIG/VIS CONDITIONS THIS MORNING WITH POTENTIAL FOR MODERATE SNOW.
EXPECT VSBYS WILL BEGIN TO IMPROVE FROM THE WEST BY MID/LATE
MORNING AS SYSTEM PASSES BY TO THE SOUTH. HOWEVER...AS LOW LEVEL
WINDS BACK TO NORTHEAST/NORTH LATER THIS MORNING AND EARLY
AFTERNOON WILL SEE POTENTIAL FOR SOME LAKE EFFECT SNOW IMPINGING
UPON CHICAGO TERMINALS...WITH 06Z RUN OF WRF EVEN INDICATING
MESOSCALE CIRCULATION DEVELOPING WITH DELTA/T APPROACHING 20 DEG.
EXPECT LAKE EFFECT TO LINGER ACROSS KGYY INTO EARLY THIS EVENING.

WINDS THEN SHIFT NORTHWEST LATER IN AFTERNOON AND INCREASE WITH
GUSTS INTO MID 20 KNOT RANGE EXPECTED TO LEAD TO BLOWING OF
NEW POWDERY SNOWFALL. HAVE HELD VSBYS IN MVFR RANGE INTO THIS
EVENING WITH STRONGEST WINDS...THEN EXPECT GRADUAL DECREASE IN
WINDS AND IMPROVEMENT IN VISIBILITY OVERNIGHT.

RATZER

&&

.MARINE...
345 AM CST

LOW PRESSURE WILL MOVE FROM THE CENTRAL PLAINS ACROSS THE LOWER OHIO
VALLEY LATER TODAY...WITH WINDS SHIFTING TO THE NORTH AND NORTHWEST
AND INCREASING TO 30 TO 35 KNOTS ACROSS LAKE MICHIGAN THIS
AFTERNOON...WITH FRIGID ARCTIC AIR SPREADING ACROSS THE LAKE. THE
COMBINATION OF STRONG WINDS...HIGH WAVES AND BITTER COLD AIR
TEMPERATURES LEADING TO HEAVY FREEZING SPRAY. HAVE ISSUED HEADLINES
FOR GALES ON SOUTHERN LAKE MICHIGAN AS WELL AS HEAVY FREEZING SPRAY
WARNING FOR ENTIRE LAKE. WINDS WILL EASE BELOW GALE FORCE ON THE
SOUTH END OF THE LAKE LATE TONIGHT...THOUGH APPEARS A PERIOD OF
20-30 KNOT WINDS AND ENTRENCHED ARCTIC AIRMASS WILL CONTINUE PRODUCE
A FREEZING SPRAY THREAT THROUGH FRIDAY/SATURDAY. SOME MODERATION OF
TEMPERATURES EXPECTED BY SATURDAY AS WINDS BACK SOUTH IN ADVANCE OF
LOW PRESSURE EXPECTED TO MOVE ACROSS THE MIDWEST AT THAT TIME.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-
     ILZ022-ILZ023-ILZ032-ILZ033-ILZ039 UNTIL MIDNIGHT THURSDAY.

     WIND CHILL WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...MIDNIGHT THURSDAY TO NOON
     FRIDAY.

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-
     INZ019...MIDNIGHT THURSDAY TO NOON FRIDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019
     UNTIL MIDNIGHT THURSDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
     LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3 PM WEDNESDAY TO 6 AM
     THURSDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
     LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
     LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3
     PM WEDNESDAY TO 6 AM SATURDAY.

&&

$$


000
FXUS63 KILX 141138
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
538 AM CST WED JAN 14 2009

.DISCUSSION...
ISSUED 235 AM CST WED JAN 14 2009

LATEST SURFACE MAP SHOWED CENTER OF CLIPPER SYSTEM ACROSS SOUTHWEST
IOWA. SNOW HAS BEEN RAPIDLY MOVING ACROSS THE CWA OVERNIGHT...WITH
THE CORE OF THE HEAVIER SNOWS GENERALLY ADVANCING EAST-SOUTHEAST
FROM A GALESBURG TO PEORIA LINE. HOWEVER...REGIONAL MOSAICS
ALREADY SHOWING THE BACK EDGE OF THE SNOW SHIELD APPROACHING WEST
CENTRAL ILLINOIS. TEMPERATURES ACROSS THE AREA HAVE BEEN RISING
OVER THE LAST SEVERAL HOURS AND HAD REACHED INTO THE LOWER 20S
AROUND JACKSONVILLE.

SHORT TERM CONCERNS WITH THE FORECAST INVOLVE THE ENDING OF THE
SNOW AND SUBSEQUENT ISSUES WITH BLOWING SNOW...FOLLOWED BY THE
BITTER COLD WEATHER THE NEXT FEW DAYS.

SHORT TERM...TODAY THROUGH FRIDAY...
LATEST RUC MODEL TAKES SURFACE LOW ACROSS THE CENTER OF THE CWA
BETWEEN 12-18Z THIS MORNING. HEAVIEST STORM TOTAL SNOWS OF AROUND
3-5 INCHES EXPECTED ROUGHLY ALONG THE I-74 CORRIDOR...WITH SOME
LOCALLY HIGHER AMOUNTS. EXPANDED THE WINTER WEATHER ADVISORY
FURTHER SOUTH TO INCLUDE AREAS DOWN TO AROUND I-70...WHERE THE
TRAJECTORY OF THE HEAVIER SNOW BANDS MAY CAUSE SOME PROBLEMS.
HOWEVER...OVERALL SOUTHERN EDGE OF THE SNOW ACCUMULATIONS SHOULD
BE FAIRLY SHARP. WINDS STILL EXPECTED TO REALLY PICK UP LATE
MORNING AND INTO THE AFTERNOON IN TIGHT PRESSURE GRADIENT BEHIND
THE DEPARTING HIGH. WITH THIS SNOW BEING RATHER FLUFFY -- SNOW TO
WATER RATIOS PROBABLY ALONG THE ORDER OF 15-20 TO 1 -- EXPECTING
BLOWING SNOW ISSUES TO DEVELOP. THIS SHOULD BEGIN TO TAPER OFF A
BIT DURING THE EVENING.

NEXT ORDER OF BUSINESS IS WITH WIND CHILL HEADLINES. WIND SPEEDS
EXPECTED TO REMAIN IN THE TEENS THROUGH THE NIGHT AS THE ARCTIC
AIRMASS INVADES THE AREA. WITH THE FRESH SNOW COVER...WENT CLOSE
TO THE COLDER NAM MOS GUIDANCE FOR TEMPERATURES...WHICH BRINGS
LOWS OF -10F OR COLDER ACROSS THE NORTHERN CWA TONIGHT AND ZERO
DEGREES ALL THE WAY DOWN TO I-70. WIND CHILLS ACROSS THE NORTHERN
HALF OF THE CWA EXPECTED TO EASILY REACH WARNING CRITERIA OF -25F
FROM ABOUT MIDNIGHT TONIGHT THROUGH NOON THURSDAY...AND WILL BE
CLOSE THURSDAY NIGHT WITH THE CORE OF THE ARCTIC HIGH JUST TO OUR
WEST. IN ORDER TO SIMPLIFY THINGS...ELECTED TO HAVE A WIND CHILL
WARNING RUNNING FROM 6 PM TONIGHT THROUGH NOON FRIDAY...AS AN
UPGRADE OF THE ORIGINAL ADVISORY IN THIS AREA. HOWEVER...THE
WARNING MAY LATER NEED TO BE DOWNGRADED THURSDAY AFTERNOON.
FURTHER SOUTH...EXPANDED THE WIND CHILL ADVISORY TO COVER THE
REMAINDER OF THE CWA...ALTHOUGH AREAS SOUTH OF I-70 WILL BE
BORDERLINE.

DEPARTURE OF HIGH PRESSURE ON FRIDAY WILL LEAD TO WARM AIR
ADVECTION...WITH AFTERNOON TEMPERATURES RECOVERING INTO THE TEENS
AFTER A BRUTAL START IN THE TEENS BELOW IN SOME AREAS.

LONG TERM...FRIDAY NIGHT THROUGH SUNDAY...

NOT MUCH CHANGE MADE TO THIS PORTION OF THE FORECAST...DUE TO
CONCENTRATION ON THE SHORT TERM PROBLEMS. NAM AND GFS HINTING AT
WAA PRECIPITATION DEVELOPMENT FRIDAY AFTERNOON AND
EVENING...MAINLY TO OUR WEST. BETTER PRECIPITATION CHANCES TO
ACCOMPANY NEXT CLIPPER SYSTEM WHICH WILL ZIP ACROSS THE AREA ON
SATURDAY. MODELS KEEPING MUCH OF THIS PRECIPITATION TO OUR NORTH
AT THIS TIME.



&&

.AVIATION...
ISSUED 525 AM CST WED JAN 14 2009

LOW PRESSURE OVER NE MISSOURI IS EXPECTED TO PASS JUST NORTH OF
SPI OVER THE NEXT SEVERAL HOURS BASED ON 3 HOURLY PRESSURE FALLS.
ON THE BACKSIDE OF THE STORM...3 HOURLY PRESSURE RISES OF 8-9 MB
INDICATING SOME STRONG WINDS PUSHING IN LATER THIS MRNG ACRS THE
WEST...AND OVR THE REMAINDER OF THE AREA THIS AFTN. AREAS THAT
RECEIVED THE SNOWFALL...FROM 2 TO 5 INCHES...MAINLY NORTH OF I-72
WL SEE SOME BLOWING AND DRIFTING OF THE POWDERY SNOW THAT WL
REDUCE VSBYS TO 1 TO 3 MILES...AND IN SOME AREAS DOWN TO ONE HALF
MILE. THE BULK OF THE STEADIER SNOWS WL SHIFT EAST OF THE AREA
OVR THE NEXT SVL HOURS...HOWEVER...AS THE STORM SHIFTS INTO ERN
IL LATER THIS MRNG...ANOTHER BAND OF SNOW SHOWERS WILL MOVE ACRS
THE AREA WITH THE COLD FRONT. THE MAIN THREAT FOR BLOWING SNOW
WL BE JUST AFTR FROPA LATE THIS MRNG WEST AND ACRS THE EAST EARLY
THIS AFTN...AND WL LAST INTO EARLY THIS EVENING WITH WINDS GRDLY
DIMINISHING AFTR 02Z. THE MVFR CIGS AND VSBYS...WITH LOCALLY IFR
AND LIFR CONDITIONS IN SNOW AND BLOWING SNOW WL IMPROVE TO VFR
CONDITIONS AT ALL FORECAST SITES AFTR 00Z.

SMITH
&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 12 PM CST FRIDAY
FOR ILZ049>057-061>063-066>068-071>073.

WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR
ILZ027>031-036>038-040>057-061.

WIND CHILL WARNING FROM 6 PM THIS EVENING TO 12 PM CST FRIDAY
FOR ILZ027>031-036>038-040>048.

&&

$$


000
FXUS63 KLOT 141020
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
415 AM CST WED JAN 14 2009

.DISCUSSION...
400 AM CST

FORECAST CONCERNS WILL CENTER ON ACCUMULATING SNOW TODAY...POTENTIAL
OF BLOWING THIS AFTERNOON/EVENING...FOLLOWED BY BITTERLY COLD
TEMPERATURES AND EXTREME WIND CHILLS. WINTER WEATHER ADVISORY FOR
SNOW AND BLOWING SNOW WILL REMAIN IN EFFECT FOR ALL OF THE FORECAST
AREA THROUGH THIS EVENING...AND A WIND CHILL WARNING HAS BEEN ISSUED
FOR ALL OF THE FORECAST AREA FROM MIDNIGHT TONIGHT THROUGH FRIDAY
MORNING.

AT 09Z...SURFACE LOW IS POSITIONED ACROSS SOUTH CENTRAL IOWA WITH
STRONGEST SFC PRESSURE FALLS CENTERED ACROSS WEST CENTRAL ILLINOIS
JUST TO THE SOUTH OF PEORIA. AS THIS LOW CONTINUES INTO WEST
CENTRAL ILLINOIS EARLY THIS MORNING...ZONE OF STRONGEST ISENTROPIC
ASCENT WILL SHIFT ACROSS SOUTHERN PORTIONS OF THE FORECAST AREA
OVER THE NEXT FEW HOURS. TIME/HEIGHT SECTIONS ALSO INDICATE MORE
FAVORABLE UVM BECOMING BASED IN PROGRESSIVELY LOWER LEVELS...IN
BETTER PROXIMITY TO DENDRITIC GROWTH ZONE. THUS...MOST EFFICIENT
SNOW ACCUMULATION PERIOD IS ANTICIPATED IN THE 12Z-15Z TIME FRAME
THIS MORNING. PLACEMENT OF STRONGEST ISENTROPIC ASCENT STILL
FAVORS HEAVIEST SNOWFALL SOUTH OF INTERSTATE 80 WHERE 3 TO 5
INCHES WILL BE POSSIBLE BEFORE TAPERS OFF FROM WEST TO EAST FROM
MID MORNING THROUGH EARLY AFTERNOON. A FEW REPORTS ACROSS EAST
CENTRAL IOWA INDICATE A FEW LOCATIONS EVEN APPROACHING 6 INCHES
BUT FEEL THAT THESE AMOUNTS WILL BE HARDER TO ATTAIN DUE TO
ISENTROPIC ASCENT LIKELY BEING A BIT STRONGER ACROSS EASTERN IOWA.
FOR THIS AFTERNOON...WILL MAINTAIN HIGHER POPS FOR CONTINUED SNOW
ACROSS MAINLY NWRN INDIANA WITH LOW LEVEL THERMAL RIDGE/WAA
CONTINUING THROUGH EARLY AFTERNOON BEFORE SHIFTING EASTWARD. LAKE
EFFECT SNOW POTENTIAL WILL INCREASE THIS AFTERNOON AS COLDER AIR
DROPS INTO THE WESTERN GREAT LAKES BEHIND THIS STORM. MODIFICATION
OF NAM BUFKIT SOUNDINGS STILL SUPPORT AROUND 500 J/KG OF LAKE
INDUCED CAPE WITH LAKE INDUCED EQUIL LEVELS INCREASING TO AROUND
10K FT. THERMALLY INDUCED CONVERGENCE ALSO EXPECTED TO ENHANCE
LAKE EFFECT SNOW POTENTIAL...ESPECIALLY BY EVENING. THE LIMITING
FACTOR FOR LAKE EFFECT SNOW POTENTIAL TODAY IS DURATION OF
FAVORABLE FETCH DUE TO PROGRESSIVE NATURE OF SOUTHEASTWARD MOVING
1045 MB HIGH INTO THE NORTHERN PLAINS TONIGHT. THIS SHOULD BACK
THE WINDS ENOUGH TO KEEP THE REAL HEAVY LAKE EFFECT SNOW ACCUMS
MORE UP THE SHORELINE INTO FAR SOUTHWEST LOWER MICHIGAN.
NONETHELESS...WHEN ADDING THE SYNOPTIC SNOW ACCUM WITH THE LAKE
EFFECT SNOW...STORM TOTAL SNOW ACCUMULATIONS ACROSS PORTIONS OF
LAKE AND PORTER COUNTIES IN NORTHWEST MAY APPROACH 6 INCHES.
OTHER CONCERN TODAY WILL BE POTENTIAL OF BLOWING SNOW AND REDUCED
VISIBILITIES. MODELS HAVE BACKED OFF A BIT ON THE MAGNITUDE OF
WIND SPEEDS...ALTHOUGH STILL HAVE LINGERING CONCERN ACROSS
SOUTHERN PORTIONS OF THE CWA WHERE BRUNT OF ISALLOBARIC PUSH IS
ANTICIPATED. ACROSS THE FAR SOUTH WIND GUSTS COULD STILL REACH
INTO THE 30 TO 35 MPH RANGE TODAY WHICH WOULD RESULT IN SOME
SIGNIFICANT BLOWING AND DRIFTING CONCERNS WITH THE NEW SNOWFALL.
ELSEWHERE...EXPECTING GUSTS GENERALLY IN THE 25 TO 30 MPH RANGE
WHICH WILL LIKELY LEAD TO BLOWING SNOW AND REDUCED
VISIBILITIES...ESPECIALLY ACROSS RURAL MORE OPEN AREAS.

SKIES WILL CLEAR FROM WEST TO EAST THIS EVENING AS MUCH DRIER
BITTERLY COLD ARCTIC AIR CONTINUES TO ADVECT SOUTHWARD...AND WIND
CHILLS OF 30 BELOW TO 40 BELOW ARE EXPECTED AFTER MIDNIGHT WITH AIR
TEMPERATURES RANGING FROM AROUND 15 BELOW FAR NORTH TO 5 TO 10 BELOW
FAR SOUTH. CURRENT FORECASTED WIND CHILLS ACROSS FAR SOUTHERN CWA
REACH AS COLD AS 30 BELOW...SO EXPECTING WIND CHILLS TO REACH
WARNING CRITERIA ACROSS MOST OR ALL OF THE CWA. WIND CHILLS MAY MOVE
BACK INTO ADVISORY RANGE DURING THE DAY THURSDAY...BUT WITH ARCTIC
HIGH APPROACHING SEE LITTLE CHANCE OF TEMPERATURE RECOVERY DURING
THE DAY. COLDEST NIGHT APPEARS TO BE THURSDAY NIGHT WITH AIR
TEMPERATURES DROPPING TO AROUND 20 BELOW NORTH CENTRAL ILLINOIS TO
10 TO 20 BELOW SOUTHERN AREAS. WIND CHILL WARNING CRITERIA WILL
LIKELY EASILY BE MET THURSDAY NIGHT. BASED ON TWO SUCCESSIVE NIGHTS
OF MEETING WIND CHILL WARNING CRITERIA...HAVE OPTED TO ISSUE A WIND
CHILL WARNING FROM AFTER MIDNIGHT TONIGHT THROUGH FRIDAY MORNING.
BITTER COLD TEMPERATURES WILL PERSIST THROUGH THE FIRST PART OF THE
WEEKEND...AND MODELS DIVERGE SOMEWHAT ON TRACK OF NEXT CLIPPER
SYSTEM WITH THE GFS A NORTHERN OUTLIER. FOR THIS FORECAST HAVE
TRENDED TO ECMWF/NAM CONSENSUS OF SFC LOW TRACKING INTO IOWA LATE
FRIDAY NIGHT WITH ANOTHER CHANCE OF AN OVERRUNNING EVENT. STILL MUCH
UNCERTAINTY REGARDING TRACK OF THIS SYSTEM...SO WILL JUST KEEP
CHANCE POPS FOR SNOW FOR FRIDAY NIGHT/SATURDAY. WITH FOCUS ON SHORT
TERM...HAVE MADE FEW CHANGES TO EXTENDED GRIDS.

MARSILI

&&

.AVIATION...
1040 PM CST

0600 UTC TAFS...CONDITIONS WILL RAPIDLY DETERIORATE SHORTLY WITH
THE APPROACH OF THE NEXT CLIPPER.

LITTLE CHANGE MADE TO THE GOING TAFS WITH THE EXCEPTION OF MOVING
UP THE ONSET OF SNOWFALL BY AN HOUR. LATEST RADAR IMAGERY SHOWS
THE SNOW SPREADING ACROSS THE MISSISSIPPI RIVER INTO NORTHWESTERN
ILLINOIS. STILL EXPECT THE SFC LOW TO QUICKLY DROP SEWD THROUGH
THE UPPER MISSOURI VALLEY WHILE THE SFC RIDGE AXIS MOVES ACROSS
LAKE MICHIGAN AND INDIANA. MID AND HIGH CLOUD HAVE OVERSPREAD THE
TERMINALS WHILE WINDS REMAIN GENERALLY LGT/VRBL AS THE SFC RIDGE
PASSES TO THE EAST. WINDS WILL BEGIN TO INCREASE AND BECOME SELY
AS THE SFC LOW TRACKS INTO NRN MISSOURI. EXPECTS CIGS/VIS TO
QUICKLY DROP THROUGH MVFR TO IFR WITH SNOW MOVING OVER RFD BY 07Z
AND THEN SPREADING EWD TO THE CHICAGO AREA TERMINALS BY 08Z. HAVE
MAINTAINED THE TEMPO GROUP FOR LIFR VIS FOR THE 12-15Z TIME
RANGE...BUT THIS MIGHT BE A LITTLE CONSERVATIVE AS WINDS WILL BE
TURNING NELY FOR A PERIOD UNTIL AT LEAST 18Z AND LAKE ENHANCEMENT
TO THE SNOWFALL MAY EXTEND THE PERIOD OF LIFR VIS.

FOLLOWING THE PASSAGE OF THE SFC LOW TO THE SOUTH AND EAST...WINDS
WILL QUICKLY INCREASE...LEADING TO BLOWING AND DRIFTING OF THE
NEWLY FALLEN SNOW. SINCE TEMPERATURES WILL BE VERY LOW FOR THE
DURATION OF THE SNOWFALL...SNOW TO LIQUID RATIOS WILL BE
HIGH...CREATING A VERY DRY SNOW. HAVE TRENDED VISBY TO IFR FOR THE
WITH BLOWING SNOW. DRIFTING SNOW WILL LIKELY CAUSE DIFFICULTIES
FOR SNOW REMOVAL CREWS.

KREIN

&&

.MARINE...
345 AM CST

LOW PRESSURE WILL MOVE FROM THE CENTRAL PLAINS ACROSS THE LOWER OHIO
VALLEY LATER TODAY...WITH WINDS SHIFTING TO THE NORTH AND NORTHWEST
AND INCREASING TO 30 TO 35 KNOTS ACROSS LAKE MICHIGAN THIS
AFTERNOON...WITH FRIGID ARCTIC AIR SPREADING ACROSS THE LAKE. THE
COMBINATION OF STRONG WINDS...HIGH WAVES AND BITTER COLD AIR
TEMPERATURES LEADING TO HEAVY FREEZING SPRAY. HAVE ISSUED HEADLINES
FOR GALES ON SOUTHERN LAKE MICHIGAN AS WELL AS HEAVY FREEZING SPRAY
WARNING FOR ENTIRE LAKE. WINDS WILL EASE BELOW GALE FORCE ON THE
SOUTH END OF THE LAKE LATE TONIGHT...THOUGH APPEARS A PERIOD OF
20-30 KNOT WINDS AND ENTRENCHED ARCTIC AIRMASS WILL CONTINUE PRODUCE
A FREEZING SPRAY THREAT THROUGH FRIDAY/SATURDAY. SOME MODERATION OF
TEMPERATURES EXPECTED BY SATURDAY AS WINDS BACK SOUTH IN ADVANCE OF
LOW PRESSURE EXPECTED TO MOVE ACROSS THE MIDWEST AT THAT TIME.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-
     ILZ022-ILZ023-ILZ032-ILZ033-ILZ039 UNTIL MIDNIGHT THURSDAY.

     WIND CHILL WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...MIDNIGHT THURSDAY TO NOON
     FRIDAY.

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-
     INZ019...MIDNIGHT THURSDAY TO NOON FRIDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019
     UNTIL MIDNIGHT THURSDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
     LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3 PM WEDNESDAY TO 6 AM
     THURSDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
     LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
     LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3
     PM WEDNESDAY TO 6 AM SATURDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ740-LMZ741-LMZ742-LMZ743...4
     PM WEDNESDAY TO 10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...4 PM
     WEDNESDAY TO 10 AM THURSDAY.

     GALE WARNING...LMZ744-LMZ745...4 PM WEDNESDAY TO 6 AM THURSDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ744-LMZ745...4 PM WEDNESDAY
TO
     NOON THURSDAY.

&&

$$


000
FXUS63 KLOT 141015
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
415 AM CST WED JAN 14 2009

.DISCUSSION...
400 AM CST

.DISCUSSION...

FORECAST CONCERNS WILL CENTER ON ACCUMULATING SNOW TODAY...POTENTIAL
OF BLOWING THIS AFTERNOON/EVENING...FOLLOWED BY BITTERLY COLD
TEMPERATURES AND EXTREME WIND CHILLS. WINTER WEATHER ADVISORY FOR
SNOW AND BLOWING SNOW WILL REMAIN IN EFFECT FOR ALL OF THE FORECAST
AREA THROUGH THIS EVENING...AND A WIND CHILL WARNING HAS BEEN ISSUED
FOR ALL OF THE FORECAST AREA FROM MIDNIGHT TONIGHT THROUGH FRIDAY
MORNING.

AT 09Z...SURFACE LOW IS POSITIONED ACROSS SOUTH CENTRAL IOWA WITH
STRONGEST SFC PRESSURE FALLS CENTERED ACROSS WEST CENTRAL ILLINOIS
JUST TO THE SOUTH OF PEORIA. AS THIS LOW CONTINUES INTO WEST
CENTRAL ILLINOIS EARLY THIS MORNING...ZONE OF STRONGEST ISENTROPIC
ASCENT WILL SHIFT ACROSS SOUTHERN PORTIONS OF THE FORECAST AREA
OVER THE NEXT FEW HOURS. TIME/HEIGHT SECTIONS ALSO INDICATE MORE
FAVORABLE UVM BECOMING BASED IN PROGRESSIVELY LOWER LEVELS...IN
BETTER PROXIMITY TO DENDRITIC GROWTH ZONE. THUS...MOST EFFICIENT
SNOW ACCUMULATION PERIOD IS ANTICIPATED IN THE 12Z-15Z TIME FRAME
THIS MORNING. PLACEMENT OF STRONGEST ISENTROPIC ASCENT STILL
FAVORS HEAVIEST SNOWFALL SOUTH OF INTERSTATE 80 WHERE 3 TO 5
INCHES WILL BE POSSIBLE BEFORE TAPERS OFF FROM WEST TO EAST FROM
MID MORNING THROUGH EARLY AFTERNOON. A FEW REPORTS ACROSS EAST
CENTRAL IOWA INDICATE A FEW LOCATIONS EVEN APPROACHING 6 INCHES
BUT FEEL THAT THESE AMOUNTS WILL BE HARDER TO ATTAIN DUE TO
ISENTROPIC ASCENT LIKELY BEING A BIT STRONGER ACROSS EASTERN IOWA.
FOR THIS AFTERNOON...WILL MAINTAIN HIGHER POPS FOR CONTINUED SNOW
ACROSS MAINLY NWRN INDIANA WITH LOW LEVEL THERMAL RIDGE/WAA
CONTINUING THROUGH EARLY AFTERNOON BEFORE SHIFTING EASTWARD. LAKE
EFFECT SNOW POTENTIAL WILL INCREASE THIS AFTERNOON AS COLDER AIR
DROPS INTO THE WESTERN GREAT LAKES BEHIND THIS STORM. MODIFICATION
OF NAM BUFKIT SOUNDINGS STILL SUPPORT AROUND 500 J/KG OF LAKE
INDUCED CAPE WITH LAKE INDUCED EQUIL LEVELS INCREASING TO AROUND
10K FT. THERMALLY INDUCED CONVERGENCE ALSO EXPECTED TO ENHANCE
LAKE EFFECT SNOW POTENTIAL...ESPECIALLY BY EVENING. THE LIMITING
FACTOR FOR LAKE EFFECT SNOW POTENTIAL TODAY IS DURATION OF
FAVORABLE FETCH DUE TO PROGRESSIVE NATURE OF SOUTHEASTWARD MOVING
1045 MB HIGH INTO THE NORTHERN PLAINS TONIGHT. THIS SHOULD BACK
THE WINDS ENOUGH TO KEEP THE REAL HEAVY LAKE EFFECT SNOW ACCUMS
MORE UP THE SHORELINE INTO FAR SOUTHWEST LOWER MICHIGAN.
NONETHELESS...WHEN ADDING THE SYNOPTIC SNOW ACCUM WITH THE LAKE
EFFECT SNOW...STORM TOTAL SNOW ACCUMULATIONS ACROSS PORTIONS OF
LAKE AND PORTER COUNTIES IN NORTHWEST MAY APPROACH 6 INCHES.
OTHER CONCERN TODAY WILL BE POTENTIAL OF BLOWING SNOW AND REDUCED
VISIBILITIES. MODELS HAVE BACKED OFF A BIT ON THE MAGNITUDE OF
WIND SPEEDS...ALTHOUGH STILL HAVE LINGERING CONCERN ACROSS
SOUTHERN PORTIONS OF THE CWA WHERE BRUNT OF ISALLOBARIC PUSH IS
ANTICIPATED. ACROSS THE FAR SOUTH WIND GUSTS COULD STILL REACH
INTO THE 30 TO 35 MPH RANGE TODAY WHICH WOULD RESULT IN SOME
SIGNIFICANT BLOWING AND DRIFTING CONCERNS WITH THE NEW SNOWFALL.
ELSEWHERE...EXPECTING GUSTS GENERALLY IN THE 25 TO 30 MPH RANGE
WHICH WILL LIKELY LEAD TO BLOWING SNOW AND REDUCED
VISIBILITIES...ESPECIALLY ACROSS RURAL MORE OPEN AREAS.

SKIES WILL CLEAR FROM WEST TO EAST THIS EVENING AS MUCH DRIER
BITTERLY COLD ARCTIC AIR CONTINUES TO ADVECT SOUTHWARD...AND WIND
CHILLS OF 30 BELOW TO 40 BELOW ARE EXPECTED AFTER MIDNIGHT WITH AIR
TEMPERATURES RANGING FROM AROUND 15 BELOW FAR NORTH TO 5 TO 10 BELOW
FAR SOUTH. CURRENT FORECASTED WIND CHILLS ACROSS FAR SOUTHERN CWA
REACH AS COLD AS 30 BELOW...SO EXPECTING WIND CHILLS TO REACH
WARNING CRITERIA ACROSS MOST OR ALL OF THE CWA. WIND CHILLS MAY MOVE
BACK INTO ADVISORY RANGE DURING THE DAY THURSDAY...BUT WITH ARCTIC
HIGH APPROACHING SEE LITTLE CHANCE OF TEMPERATURE RECOVERY DURING
THE DAY. COLDEST NIGHT APPEARS TO BE THURSDAY NIGHT WITH AIR
TEMPERATURES DROPPING TO AROUND 20 BELOW NORTH CENTRAL ILLINOIS TO
10 TO 20 BELOW SOUTHERN AREAS. WIND CHILL WARNING CRITERIA WILL
LIKELY EASILY BE MET THURSDAY NIGHT. BASED ON TWO SUCCESSIVE NIGHTS
OF MEETING WIND CHILL WARNING CRITERIA...HAVE OPTED TO ISSUE A WIND
CHILL WARNING FROM AFTER MIDNIGHT TONIGHT THROUGH FRIDAY MORNING.
BITTER COLD TEMPERATURES WILL PERSIST THROUGH THE FIRST PART OF THE
WEEKEND...AND MODELS DIVERGE SOMEWHAT ON TRACK OF NEXT CLIPPER
SYSTEM WITH THE GFS A NORTHERN OUTLIER. FOR THIS FORECAST HAVE
TRENDED TO ECMWF/NAM CONSENSUS OF SFC LOW TRACKING INTO IOWA LATE
FRIDAY NIGHT WITH ANOTHER CHANCE OF AN OVERRUNNING EVENT. STILL MUCH
UNCERTAINTY REGARDING TRACK OF THIS SYSTEM...SO WILL JUST KEEP
CHANCE POPS FOR SNOW FOR FRIDAY NIGHT/SATURDAY. WITH FOCUS ON SHORT
TERM...HAVE MADE FEW CHANGES TO EXTENDED GRIDS.

MARSILI

&&

.AVIATION...
1040 PM CST

0600 UTC TAFS...CONDITIONS WILL RAPIDLY DETERIORATE SHORTLY WITH
THE APPROACH OF THE NEXT CLIPPER.

LITTLE CHANGE MADE TO THE GOING TAFS WITH THE EXCEPTION OF MOVING
UP THE ONSET OF SNOWFALL BY AN HOUR. LATEST RADAR IMAGERY SHOWS
THE SNOW SPREADING ACROSS THE MISSISSIPPI RIVER INTO NORTHWESTERN
ILLINOIS. STILL EXPECT THE SFC LOW TO QUICKLY DROP SEWD THROUGH
THE UPPER MISSOURI VALLEY WHILE THE SFC RIDGE AXIS MOVES ACROSS
LAKE MICHIGAN AND INDIANA. MID AND HIGH CLOUD HAVE OVERSPREAD THE
TERMINALS WHILE WINDS REMAIN GENERALLY LGT/VRBL AS THE SFC RIDGE
PASSES TO THE EAST. WINDS WILL BEGIN TO INCREASE AND BECOME SELY
AS THE SFC LOW TRACKS INTO NRN MISSOURI. EXPECTS CIGS/VIS TO
QUICKLY DROP THROUGH MVFR TO IFR WITH SNOW MOVING OVER RFD BY 07Z
AND THEN SPREADING EWD TO THE CHICAGO AREA TERMINALS BY 08Z. HAVE
MAINTAINED THE TEMPO GROUP FOR LIFR VIS FOR THE 12-15Z TIME
RANGE...BUT THIS MIGHT BE A LITTLE CONSERVATIVE AS WINDS WILL BE
TURNING NELY FOR A PERIOD UNTIL AT LEAST 18Z AND LAKE ENHANCEMENT
TO THE SNOWFALL MAY EXTEND THE PERIOD OF LIFR VIS.

FOLLOWING THE PASSAGE OF THE SFC LOW TO THE SOUTH AND EAST...WINDS
WILL QUICKLY INCREASE...LEADING TO BLOWING AND DRIFTING OF THE
NEWLY FALLEN SNOW. SINCE TEMPERATURES WILL BE VERY LOW FOR THE
DURATION OF THE SNOWFALL...SNOW TO LIQUID RATIOS WILL BE
HIGH...CREATING A VERY DRY SNOW. HAVE TRENDED VISBY TO IFR FOR THE
WITH BLOWING SNOW. DRIFTING SNOW WILL LIKELY CAUSE DIFFICULTIES
FOR SNOW REMOVAL CREWS.

KREIN

&&

.MARINE...
345 AM CST

LOW PRESSURE WILL MOVE FROM THE CENTRAL PLAINS ACROSS THE LOWER OHIO
VALLEY LATER TODAY...WITH WINDS SHIFTING TO THE NORTH AND NORTHWEST
AND INCREASING TO 30 TO 35 KNOTS ACROSS LAKE MICHIGAN THIS
AFTERNOON...WITH FRIGID ARCTIC AIR SPREADING ACROSS THE LAKE. THE
COMBINATION OF STRONG WINDS...HIGH WAVES AND BITTER COLD AIR
TEMPERATURES LEADING TO HEAVY FREEZING SPRAY. HAVE ISSUED HEADLINES
FOR GALES ON SOUTHERN LAKE MICHIGAN AS WELL AS HEAVY FREEZING SPRAY
WARNING FOR ENTIRE LAKE. WINDS WILL EASE BELOW GALE FORCE ON THE
SOUTH END OF THE LAKE LATE TONIGHT...THOUGH APPEARS A PERIOD OF
20-30 KNOT WINDS AND ENTRENCHED ARCTIC AIRMASS WILL CONTINUE PRODUCE
A FREEZING SPRAY THREAT THROUGH FRIDAY/SATURDAY. SOME MODERATION OF
TEMPERATURES EXPECTED BY SATURDAY AS WINDS BACK SOUTH IN ADVANCE OF
LOW PRESSURE EXPECTED TO MOVE ACROSS THE MIDWEST AT THAT TIME.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-
     ILZ022-ILZ023-ILZ032-ILZ033-ILZ039 UNTIL MIDNIGHT THURSDAY.

     WIND CHILL WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...MIDNIGHT THURSDAY TO NOON
     FRIDAY.

IN...WIND CHILL WARNING...INZ001-INZ002-INZ010-INZ011-
     INZ019...MIDNIGHT THURSDAY TO NOON FRIDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019
     UNTIL MIDNIGHT THURSDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
     LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3 PM WEDNESDAY TO 6 AM
     THURSDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
     LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
     LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3
     PM WEDNESDAY TO 6 AM SATURDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ740-LMZ741-LMZ742-LMZ743...4
     PM WEDNESDAY TO 10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...4 PM
     WEDNESDAY TO 10 AM THURSDAY.

     GALE WARNING...LMZ744-LMZ745...4 PM WEDNESDAY TO 6 AM THURSDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ744-LMZ745...4 PM WEDNESDAY TO
     NOON THURSDAY.

&&

$$


000
FXUS63 KILX 140836
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
236 AM CST WED JAN 14 2009

.DISCUSSION...
ISSUED 235 AM CST WED JAN 14 2009

LATEST SURFACE MAP SHOWED CENTER OF CLIPPER SYSTEM ACROSS SOUTHWEST
IOWA. SNOW HAS BEEN RAPIDLY MOVING ACROSS THE CWA OVERNIGHT...WITH
THE CORE OF THE HEAVIER SNOWS GENERALLY ADVANCING EAST-SOUTHEAST
FROM A GALESBURG TO PEORIA LINE. HOWEVER...REGIONAL MOSAICS
ALREADY SHOWING THE BACK EDGE OF THE SNOW SHIELD APPROACHING WEST
CENTRAL ILLINOIS. TEMPERATURES ACROSS THE AREA HAVE BEEN RISING
OVER THE LAST SEVERAL HOURS AND HAD REACHED INTO THE LOWER 20S
AROUND JACKSONVILLE.

SHORT TERM CONCERNS WITH THE FORECAST INVOLVE THE ENDING OF THE
SNOW AND SUBSEQUENT ISSUES WITH BLOWING SNOW...FOLLOWED BY THE
BITTER COLD WEATHER THE NEXT FEW DAYS.


SHORT TERM...TODAY THROUGH FRIDAY...
LATEST RUC MODEL TAKES SURFACE LOW ACROSS THE CENTER OF THE CWA
BETWEEN 12-18Z THIS MORNING. HEAVIEST STORM TOTAL SNOWS OF AROUND
3-5 INCHES EXPECTED ROUGHLY ALONG THE I-74 CORRIDOR...WITH SOME
LOCALLY HIGHER AMOUNTS. EXPANDED THE WINTER WEATHER ADVISORY
FURTHER SOUTH TO INCLUDE AREAS DOWN TO AROUND I-70...WHERE THE
TRAJECTORY OF THE HEAVIER SNOW BANDS MAY CAUSE SOME PROBLEMS.
HOWEVER...OVERALL SOUTHERN EDGE OF THE SNOW ACCUMULATIONS SHOULD
BE FAIRLY SHARP. WINDS STILL EXPECTED TO REALLY PICK UP LATE
MORNING AND INTO THE AFTERNOON IN TIGHT PRESSURE GRADIENT BEHIND
THE DEPARTING HIGH. WITH THIS SNOW BEING RATHER FLUFFY -- SNOW TO
WATER RATIOS PROBABLY ALONG THE ORDER OF 15-20 TO 1 -- EXPECTING
BLOWING SNOW ISSUES TO DEVELOP. THIS SHOULD BEGIN TO TAPER OFF A
BIT DURING THE EVENING.

NEXT ORDER OF BUSINESS IS WITH WIND CHILL HEADLINES. WIND SPEEDS
EXPECTED TO REMAIN IN THE TEENS THROUGH THE NIGHT AS THE ARCTIC
AIRMASS INVADES THE AREA. WITH THE FRESH SNOW COVER...WENT CLOSE
TO THE COLDER NAM MOS GUIDANCE FOR TEMPERATURES...WHICH BRINGS
LOWS OF -10F OR COLDER ACROSS THE NORTHERN CWA TONIGHT AND ZERO
DEGREES ALL THE WAY DOWN TO I-70. WIND CHILLS ACROSS THE NORTHERN
HALF OF THE CWA EXPECTED TO EASILY REACH WARNING CRITERIA OF -25F
FROM ABOUT MIDNIGHT TONIGHT THROUGH NOON THURSDAY...AND WILL BE
CLOSE THURSDAY NIGHT WITH THE CORE OF THE ARCTIC HIGH JUST TO OUR
WEST. IN ORDER TO SIMPLIFY THINGS...ELECTED TO HAVE A WIND CHILL
WARNING RUNNING FROM 6 PM TONIGHT THROUGH NOON FRIDAY...AS AN
UPGRADE OF THE ORIGINAL ADVISORY IN THIS AREA. HOWEVER...THE
WARNING MAY LATER NEED TO BE DOWNGRADED THURSDAY AFTERNOON.
FURTHER SOUTH...EXPANDED THE WIND CHILL ADVISORY TO COVER THE
REMAINDER OF THE CWA...ALTHOUGH AREAS SOUTH OF I-70 WILL BE
BORDERLINE.

DEPARTURE OF HIGH PRESSURE ON FRIDAY WILL LEAD TO WARM AIR
ADVECTION...WITH AFTERNOON TEMPERATURES RECOVERING INTO THE TEENS
AFTER A BRUTAL START IN THE TEENS BELOW IN SOME AREAS.


LONG TERM...FRIDAY NIGHT THROUGH SUNDAY...

NOT MUCH CHANGE MADE TO THIS PORTION OF THE FORECAST...DUE TO
CONCENTRATION ON THE SHORT TERM PROBLEMS. NAM AND GFS HINTING AT
WAA PRECIPITATION DEVELOPMENT FRIDAY AFTERNOON AND
EVENING...MAINLY TO OUR WEST. BETTER PRECIPITATION CHANCES TO
ACCOMPANY NEXT CLIPPER SYSTEM WHICH WILL ZIP ACROSS THE AREA ON
SATURDAY. MODELS KEEPING MUCH OF THIS PRECIPITATION TO OUR NORTH
AT THIS TIME.

GEELHART
&&

.AVIATION...
ISSUED 1149 PM CST TUE JAN 13 2009...FOR THE 06Z TAFS

CLIPPER SNOWS DEVELOPING SLIGHTLY AHEAD OF ORIGINAL FORECAST.
UPDATED PIA/BMI/SPI TO ACCOUNT FOR SOONER ONSET OF SNOW AND MVFR
VIS/CIGS. ISENTROPIC LIFT IS INTENSIFYING AHEAD OF THE LOW
CENTER...WHICH IS JUST ENTERING NW MO AT 05Z. PRESSURE FALLS SHOW
THE LOW SHOULD TRACK OVER OR JUST S OF SPI AND DEC AS IT HEADS
INTO INDIANA BY 18Z WED.

RADAR TRENDS SHOW AN BAND OF LIFR VIS/CIG SNOWS WILL PUSH ACROSS
THE TAF SITES SHORTLY AFTER 06Z FOR A COUPLE HOURS. ADDED SOME
TEMPOS FOR VLIFR VIS/CIGS EARLY IN THE TAF PERIOD...MAINLY FOR
PIA/BMI. SPC MESO DISCUSSION SHOWS THAT THIS INITIAL WAVE OF SNOW
MAY BE THE MAIN EVENT...AND THAT THE SECOND WAVE OF HEAVIER SNOW
AROUND 12Z MAY NOT MATERIALIZE AS THE MODELS INDICATE. WILL KEEP
SOME MENTION OF LOWER VIS/CIGS AROUND 12Z ACROSS THE NORTH FOR
NOW. SATELLITE TRENDS SHOW A DRYING TREND SOONER THAN MODELS
INDICATE...AND WARMER CLOUD TOPS ARE ENTERING W IOWA ALREADY.

SNOWFALL AMOUNTS MAY NOT REACH 5 INCH TOTALS...BUT 2 TO 4 INCHES
STILL LOOKS GOOD. WILL KEEP BLSN FOR WED AFTERNOON
EVERYWHERE...AS NW WINDS CRANK UP TO 20G30KT. EVEN A LITTLE SNOW
ON THE GROUND WILL BLOW AND REDUCE VIS TO 1SM OR LESS AT TIMES.

WINDS SHOULD REMAIN GUSTY WED EVENING AS THE COLD AIR RUSHES INTO
THE AREA. SKIES WILL CLEAR OUT FROM W TO E WED EVE.

SHIMON
&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 12 PM CST FRIDAY
FOR ILZ049>057-061>063-066>068-071>073.

WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR
ILZ027>031-036>038-040>057-061.

WIND CHILL WARNING FROM 6 PM THIS EVENING TO 12 PM CST FRIDAY
FOR ILZ027>031-036>038-040>048.

&&

$$


000
FXUS63 KILX 140549
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1149 PM CST TUE JAN 13 2009

.DISCUSSION...
ISSUED 858 PM CST TUE JAN 13 2009

SNOW IS SPREADING INTO CENTRAL IL PRETTY MUCH AS EXPECTED. THE
LATEST MODEL RUNS SHOW THE CLIPPER IS EXPECTED TO FOLLOW A
SLIGHTLY FARTHER SOUTH TRACK THAN THE 12Z MODELS SHOWED. THE
HEAVIER SNOW BAND MAY EXTEND A LITTLE FARTHER SOUTH OF
I-74...POSSIBLY AS FAR SOUTH AS LINCOLN. THE 02Z RUC IS SHOWING
THIS TREND...AS WELL AS THE 18Z GFS. THE 00Z NAM IS IN...AND SHOWS
THE HEAVY AXIS ALONG I-74...NOT NORTH OF I-74. THERE ARE EVEN
INDICATIONS OF A FEW LOCATIONS GETTING NEAR THE 6 INCH MARK. THE
COLD AIR AND FLUFFY NATURE OF THE SNOW WILL ALLOW THE SNOW TO PILE
UP QUICKLY. WILL KEEP THE ADVISORY GOING INSTEAD OF A
WARNING...AS THE MAJORITY OF THE AREA SHOULD REMAIN LESS THAN 6
INCHES. EVEN WITH SLIGHTLY HIGHER SNOW TOTALS... MOST AREAS NORTH
OF LINCOLN WILL BE IN THE 3 TO 5 INCH RANGE ON THE HIGH SIDE.

BLOWING ON WEDNESDAY WILL MAKE MEASURING THE SNOW QUITE DIFFICULT.
DRIFTS AND REDUCED VISIBILITY IN THE BLOWING SNOW WILL MAKE TRAVEL
QUITE DIFFICULT ON WEDNESDAY...ESPECIALLY ON NORTH-SOUTH ROADS.
ACTUALLY...WINDS WILL BE NW...SO EVEN EAST-WEST ROADS WILL SEE
PLENTY OF DRIFTING.

I BUMPED UP THE SNOW TOTALS IN THE GRIDS TO ACCOUNT FOR RAPID SNOW
ACCUMS BETWEEN 3 AM AND 8 AM.

LOW TEMPS HAVE ALREADY BEEN REACHED...AND SOUTHERLY FLOW AND
INCREASING CLOUDS HAS TURNED TEMP TRENDS WARMER. THAT WILL
CONTINUE THE REST OF THE NIGHT...STEADY OR SLOWLY RISING TEMPS.

SNOW WILL CONTINUE WED MORNING IN THE NE THIRD OF THE CWA...WITH
ACCUMULATIONS CONTINUING UNTIL LATE MORNING. A VERY BLUSTERY DAY
IS IN STORE FOR WED.

UPDATED GRIDS AND ZONES WILL BE AVAILABLE SHORTLY.

SHIMON

&&

.AVIATION...
ISSUED 1149 PM CST TUE JAN 13 2009...FOR THE 06Z TAFS

CLIPPER SNOWS DEVELOPING SLIGHTLY AHEAD OF ORIGINAL FORECAST.
UPDATED PIA/BMI/SPI TO ACCOUNT FOR SOONER ONSET OF SNOW AND MVFR
VIS/CIGS. ISENTROPIC LIFT IS INTENSIFYING AHEAD OF THE LOW
CENTER...WHICH IS JUST ENTERING NW MO AT 05Z. PRESSURE FALLS SHOW
THE LOW SHOULD TRACK OVER OR JUST S OF SPI AND DEC AS IT HEADS
INTO INDIANA BY 18Z WED.

RADAR TRENDS SHOW AN BAND OF LIFR VIS/CIG SNOWS WILL PUSH ACROSS
THE TAF SITES SHORTLY AFTER 06Z FOR A COUPLE HOURS. ADDED SOME
TEMPOS FOR VLIFR VIS/CIGS EARLY IN THE TAF PERIOD...MAINLY FOR
PIA/BMI. SPC MESO DISCUSSION SHOWS THAT THIS INITIAL WAVE OF SNOW
MAY BE THE MAIN EVENT...AND THAT THE SECOND WAVE OF HEAVIER SNOW
AROUND 12Z MAY NOT MATERIALIZE AS THE MODELS INDICATE. WILL KEEP
SOME MENTION OF LOWER VIS/CIGS AROUND 12Z ACROSS THE NORTH FOR
NOW. SATELLITE TRENDS SHOW A DRYING TREND SOONER THAN MODELS
INDICATE...AND WARMER CLOUD TOPS ARE ENTERING W IOWA ALREADY.

SNOWFALL AMOUNTS MAY NOT REACH 5 INCH TOTALS...BUT 2 TO 4 INCHES
STILL LOOKS GOOD. WILL KEEP BLSN FOR WED AFTERNOON
EVERYWHERE...AS NW WINDS CRANK UP TO 20G30KT. EVEN A LITTLE SNOW
ON THE GROUND WILL BLOW AND REDUCE VIS TO 1SM OR LESS AT TIMES.

WINDS SHOULD REMAIN GUSTY WED EVENING AS THE COLD AIR RUSHES INTO
THE AREA. SKIES WILL CLEAR OUT FROM W TO E WED EVE.

SHIMON
&&

.PREV DISCUSSION...
ISSUED 334 PM CST TUE JAN 13 2009

LATEST SURFACE ANALYSIS HAD A SKINNY RIDGE OF HIGH PRESSURE
EXTENDING FROM THE SOUTHERN PLAINS INTO THE UPPER MIDWEST. FURTHER
UPSTREAM...THE LATEST IN OUR RECENT SERIES OF CLIPPER SYSTEMS WAS
OVER THE NORTHERN HIGH PLAINS. THE SNOW CHANCES/AMOUNTS WITH THE
APPROACHING CLIPPER LATE TONIGHT INTO WEDNESDAY...AS WELL AS HOW
COLD IT WILL BE IN THE WAKE OF THE SYSTEM OVER THE NEXT COUPLE OF
DAYS ARE THE PRIMARY FORECAST CONCERNS THIS AFTERNOON.

12Z MODELS IN GOOD OVERALL AGREEMENT WITH THE CLIPPER SYSTEM...
THOUGH THERE ARE SUBTLE DIFFERENCES IN THE TRACK OF THE STORM. STILL
PREFER THE SOUTHERN MOST TRACK OF THE GFS...GIVEN THE DIGGING NATURE
OF THE MEAN UPPER TROF...WHICH WOULD SUPPORT THE HEAVIEST SNOWFALL
ALONG AND NORTH OF THE I-74 CORRIDOR. GUIDANCE TEMPERATURES STILL
SHOWING SOME SPREAD...LIKELY A RESULT OF THE STORM TRACK DIFFERENCES
AND RESULTING DIFFERENCES IN SNOWFALL. WILL TEND TO FOLLOW A BLEND
OF MODEL TEMPERATURES GIVEN LINGERING UNCERTAINTY.

SHORT TERM...TONIGHT THROUGH FRIDAY...

TONIGHT AND WEDNESDAY...CLIPPER WILL RAPIDLY DIVE SOUTHEAST
TONIGHT...LIKELY REACHING WEST CENTRAL ILLINOIS BY 12Z WEDNESDAY.
THE SYSTEM WILL CONTINUE EAST TO SOUTHERN OHIO BY 00Z THURSDAY.
STRONG WAA/ISENTROPIC LIFT AND THE CORRESPONDING LOW CONDENSATION
PRESSURE DEFICITS SUPPORT SNOW BREAKING OUT FROM NORTHWEST TO
SOUTHEAST ACROSS THE FORECAST AREA OVERNIGHT...LINGERING INTO EARLY
WEDNESDAY AS THE UPPER WAVE/JET MOVE THROUGH. THE FORCING
OVERNIGHT IS QUITE STRONG...BUT THE PERIOD OF STRONG FORCING IS
BRIEF AND THE AVAILABLE MOISTURE LIMITED. STILL...THE HIGH SNOW TO
WATER RATIO EXPECTED DUE TO THE COLD AIRMASS SUPPORTS A BAND OF
2-4 INCH SNOWS...PRIMARILY ALONG AND NORTH OF THE I-74 CORRIDOR.
LOWER SNOW TOTALS ARE EXPECTED AS YOU HEAD SOUTH FROM I-74. THERE
IS NOT A STRONG SIGNAL OF A GOOD DEFORMATION SNOW BAND ON THE BACK
SIDE OF THE CLIPPER...SO EXPECT SNOWS TO TAPER OFF PRETTY QUICKLY
WEDNESDAY. HOWEVER...AS WINDS PICK UP ON THE BACK SIDE OF THE
CLIPPER SYSTEM...WITH WIND GUSTS OVER 30 MPH...BLOWING AND
DRIFTING SNOW WILL DEVELOP ACROSS AREAS THAT RECEIVED ACCUMULATING
SNOW. THE COMBINATION OF ACCUMULATING AND BLOWING SNOW ACROSS
NORTHERN SECTIONS OF THE FORECAST AREA WILL MAKE TRAVEL TRICKY.
SO...HAVE ISSUED A WINTER WEATHER ADVISORY IN NORTHERN SECTIONS OF
THE FORECAST AREA OVERNIGHT AND WEDNESDAY.

WEDNESDAY NIGHT THROUGH FRIDAY...COLD AIR WILL CONTINUE TO SURGE
INTO THE REGION INTO AT LEAST THURSDAY NIGHT ON NORTHWEST WINDS AS
AN ARCTIC HIGH BUILDS THROUGH ILLINOIS. THIS COLD AIR WILL BE
ENHANCED ACROSS THE NORTHERN SECTIONS OF THE FORECAST AREA WHERE
SNOW COVER WILL EXIST. THIS COLD AIR WILL RESULT IN TWO NIGHTS OF
NEAR OR SUB ZERO LOWS WEDNESDAY NIGHT AND THURSDAY NIGHT AND A DAY
OF SINGLE DIGIT HIGHS ON THURSDAY. THESE BITTERLY COLD TEMPERATURES
WILL COMBINE WITH THE WIND TO PRODUCE WIND CHILL VALUES OF -15F OR
COLDER FOR MUCH OF THE PERIOD. HAVE DECIDED TO ISSUE A WIND CHILL
ADVISORY FROM 06Z THURSDAY-18Z FRIDAY FOR AREAS NORTH OF I-70 TO
ACCOUNT FOR THE BITTERLY COLD CONDITIONS. WHILE AREAS SOUTH OF I-70
SHOULD REMAIN ABOVE ADVISORY CRITERIA DUE TO SLIGHTLY WARMER
TEMPERATURES AND LITTLE/NO SNOW COVER...IT WILL STILL BE QUITE COLD
THERE TOO.

TEMPERATURES WILL BEGIN TO MODERATE SOME ON FRIDAY AS THE ARCTIC
HIGH SHIFTS EAST AND WINDS BEGIN TO TURN TO THE SOUTHWEST.

LONG TERM...SATURDAY THROUGH TUESDAY...MODELS/ENSEMBLES REMAIN IN
REASONABLE AGREEMENT WITH THE MEAN FLOW PATTERN THROUGH MUCH OF THE
EXTENDED FORECAST PERIOD...WITH A RIDGE WEST/TROF EAST CONFIGURATION
ACROSS NORTH AMERICA. HOWEVER...THE AGREEMENT WITH RESPECT TO THE
SMALLER SCALE WAVES DIVING INTO THE MEAN TROF IS STILL NOT VERY GOOD
AND GETS INCREASINGLY POOR WITH TIME. THE CORE OF THE COLDEST AIR
WITHIN THE MEAN EASTERN NORTH AMERICAN TROF IS STILL EXPECTED TO
RETREAT TO NEW ENGLAND AND EASTERN CANADA THROUGH THE PERIOD AND
THIS WILL RESULT IN A MODERATION OF TEMPERATURES. AS IN RECENT
DAYS...WILL NOT HAVE ANY MENTION OF PRECIPITATION AT THIS TIME.
WHILE SEVERAL SHORT WAVE IMPULSES ARE EXPECTED TO DIVE INTO THE MEAN
UPPER TROF DURING THE PERIOD...THESE IMPULSES WILL BE MOISTURE
STARVED AND NO STRONG MODEL CONSENSUS EXISTS ON THEIR TIMING OR
TRACK. HOWEVER...THE TRACK PREDICTED BY A BULK OF THE SOLUTIONS
SUGGESTS MOST OF THE PRECIPITATION SHOULD STAY TO OUR NORTH AND
EAST. THE MODELS ARE SIGNALING A TRANSITION TO A MORE ZONAL FLOW
PATTERN JUST BEYOND THIS FORECAST PERIOD...BUT ARE CURRENTLY ALL
OVER THE PLACE IN HOW WE WILL GET THERE. STAY TUNED.

BAK


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 PM CST WEDNESDAY FOR ILZ027>031-
036>038-040>046.

WIND CHILL ADVISORY FROM MIDNIGHT WEDNESDAY NIGHT TO 12 PM CST
FRIDAY FOR ILZ027>031-036>038-040>057-061.

&&

$$


000
FXUS63 KLOT 140440
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1040 PM CST TUE JAN 13 2009

.DISCUSSION...
1017 PM CST

AS MENTIONED IN PREVIOUS AFD DECIDED TO EXPAND WINTER WEATHER
ADVISORY TO ENCOMPASS REMAINDER OF THE CWA TO COVER BOTH FALLING
THEN EVENTUAL BLOWING SNOW. AT 04Z SURFACE ANALYSIS HAD A 1010MB
LOW NEAR THE SD/IA/NE BORDER...WHICH IS TRACKING A BIT FARTHER
NORTH THAN 12Z/18 GUIDANCE HAD SUGGESTED. STRONGEST 3 HOUR
PRESSURE FALLS WOULD SUGGEST A CONTINUED ESE TRACK TOWARD CENTRAL
ILLINOIS. NUMERICAL GUIDANCE AND EMPIRICAL RULES OF THUMB WOULD
PLACE THE AXIS OF HEAVIEST SNOWFALL RIGHT ACROSS THE SOUTHERN
THIRD OF OUR CWA.

SNOWFALL AMOUNTS WILL BE TRICKY. MOISTURE IS LIMITED AND GARCIA
METHOD WOULD SUGGEST TOTALS OF 2-4" IN THE HEAVIEST BAND...HOWEVER
DEEP LAYER WITH FAVORABLE DENDRITIC TEMPS AND VERY COLD AIRMASS
SHOULD ALLOW FOR A PARTICULARLY DRY AND FLOOFFY SNOW. WOULD
GENERALLY EXPECT SNOW:LIQUID RATIOS QUITE HIGH LIKELY IN THE
20-30:1 NEIGHBORHOOD. GOING FORECAST SNOWFALL TOTALS LOOK RIGHT ON
TARGET AND DIDN`T MAKE ANY CHANGES...WHILE TOTALS WILL PROBABLY
END UP ON THE BOTTOM END OF OR JUST BELOW ADVISORY CRITERIA BITTER
COLD TEMPS SHOULD CAUSE SNOW TO IMMEDIATELY ACCUMULATE ON
ROADWAYS. IN ADDITION...PEAK SNOW INTENSITY WILL LIKELY BE AROUND
MORNING RUSH HOUR LIKELY RESULTING IN VERY DIFFICULT TRAVEL.

ONLY REAL CHANGE TO GOING FORECAST BESIDES HOISTING THE ADVISORY
WAS TO MOVE UP THE END TIME OF THE SNOW TO MIDDAY WEDNESDAY...WITH
THE ONE EXCEPTION BEING NEAR THE LAKE IN NW INDIANA. EASTERLY
WINDS OFF THE LAKE COULD ALLOW FOR SOME SLIGHTLY ENHANCED TOTALS
NEAR THE LAKE IN NE IL...THOUGH FETCH LOOKS SHORT ENOUGH TO NOT BE
A BIG PROBLEM IN ILLINOIS. BY AFTERNOON WINDS TURN MORE NORTHERLY
AND FETCH INCREASES CONSIDERABLY SO WILL PROBABLY SEE LAKE EFFECT
SNOW SHOWERS FOR A TIME IN OUR NW IN COUNTIES...THOUGH EXPECT
DURATION OF THE LAKE EFFECT TO BE SHORT ENOUGH TO PRECLUDE MOST
AREAS FROM EXCEEDING 6 INCHES TOTAL FROM SYNOPTIC/LAKE EVENT.
MAJORITY OF THE LAKE EFFECT SHOULD SHIFT EAST INTO INDIANA
WEDNESDAY EVENING WITH MAIN LINGERING THREAT BEING
BLOWING/DRIFTING IN OPEN/RURAL AREAS WHICH SHOULD ALSO SUBSIDE BY
LATE EVENING AS WINDS DECREASE.

IZZI

&&

.AVIATION...
1040 PM CST

0600 UTC TAFS...CONDITIONS WILL RAPIDLY DETERIORATE SHORTLY WITH
THE APPROACH OF THE NEXT CLIPPER.

LITTLE CHANGE MADE TO THE GOING TAFS WITH THE EXCEPTION OF MOVING
UP THE ONSET OF SNOWFALL BY AN HOUR. LATEST RADAR IMAGERY SHOWS
THE SNOW SPREADING ACROSS THE MISSISSIPPI RIVER INTO NORTHWESTERN
ILLINOIS. STILL EXPECT THE SFC LOW TO QUICKLY DROP SEWD THROUGH
THE UPPER MISSOURI VALLEY WHILE THE SFC RIDGE AXIS MOVES ACROSS
LAKE MICHIGAN AND INDIANA. MID AND HIGH CLOUD HAVE OVERSPREAD THE
TERMINALS WHILE WINDS REMAIN GENERALLY LGT/VRBL AS THE SFC RIDGE
PASSES TO THE EAST. WINDS WILL BEGIN TO INCREASE AND BECOME SELY
AS THE SFC LOW TRACKS INTO NRN MISSOURI. EXPECTS CIGS/VIS TO
QUICKLY DROP THROUGH MVFR TO IFR WITH SNOW MOVING OVER RFD BY 07Z
AND THEN SPREADING EWD TO THE CHICAGO AREA TERMINALS BY 08Z. HAVE
MAINTAINED THE TEMPO GROUP FOR LIFR VIS FOR THE 12-15Z TIME
RANGE...BUT THIS MIGHT BE A LITTLE CONSERVATIVE AS WINDS WILL BE
TURNING NELY FOR A PERIOD UNTIL AT LEAST 18Z AND LAKE ENHANCEMENT
TO THE SNOWFALL MAY EXTEND THE PERIOD OF LIFR VIS.

FOLLOWING THE PASSAGE OF THE SFC LOW TO THE SOUTH AND EAST...WINDS
WILL QUICKLY INCREASE...LEADING TO BLOWING AND DRIFTING OF THE
NEWLY FALLEN SNOW. SINCE TEMPERATURES WILL BE VERY LOW FOR THE
DURATION OF THE SNOWFALL...SNOW TO LIQUID RATIOS WILL BE
HIGH...CREATING A VERY DRY SNOW. HAVE TRENDED VISBY TO IFR FOR THE
WITH BLOWING SNOW. DRIFTING SNOW WILL LIKELY CAUSE DIFFICULTIES
FOR SNOW REMOVAL CREWS.

KREIN

&&

.MARINE...
210 PM CST

WINDS HAVE DIMINISHED ACROSS THE LAKE THIS AFTERNOON AND THEREFORE
HAVE DROPPED THE GALE AND FREEZING SPRAY WARNINGS. WINDS WILL
CONTINUE TO DIMINISH OVERNIGHT AS A RIDGE OF HIGH PRESSURE MOVES
IN ACROSS THE REGION. A LOW PRESSURE SYSTEM WILL DROP DOWN INTO
CENTRAL ILLINOIS WEDNESDAY MORNING AND THEN TRACK EASTWARD THROUGH
THE OHIO RIVER VALLEY INTO THURSDAY MORNING. WINDS WILL BE ON THE
INCREASE THURSDAY MORNING AS THE LOW REACHES THE MID ATLANTIC
COAST AND A STRONG RIDGE OF HIGH PRESSURE MOVES IN ACROSS THE
GREAT LAKES. WILL KEEP THE GALE WATCH GOING FOR THE MOMENT AS
WINDS STILL MAY GUST UP TO GALE FORCE ON THURSDAY.  THIS RIDGE
WILL SLOWLY MOVE OFF TOWARD THE SOUTHEAST US BY SATURDAY AS THE
NEXT SYSTEM TAKES AIM ON THE LAKES.

VISIBLE SATELLITE FROM TODAY REVEALS THAT THERE IS FAIRLY
EXTENSIVE ICE COVER ACROSS THE NEARSHORE ZONES EXCEPT FOR THE
FURTHEST ZONE TO THE EAST FROM BURNS HARBOR TO MICHIGAN CITY.
THEREFORE...WILL BE DROPPING THE MENTION OF WAVES IN THE NEARSHORE
FORECAST.

HALBACH

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-
     ILZ022-ILZ023-ILZ032-ILZ033-ILZ039 UNTIL MIDNIGHT THURSDAY.

     WIND CHILL WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...MIDNIGHT THURSDAY TO NOON
     FRIDAY.

IN...WIND CHILL WATCH...INZ001-INZ002-INZ010-INZ011-INZ019...MIDNIGHT
     THURSDAY TO NOON FRIDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019
     UNTIL MIDNIGHT THURSDAY.

LM...GALE WATCH...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...MIDNIGHT THURSDAY TO 1 PM THURSDAY.

&&

$$


000
FXUS63 KLOT 140440
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1040 PM CST TUE JAN 13 2009

.DISCUSSION...
1017 PM CST

AS MENTIONED IN PREVIOUS AFD DECIDED TO EXPAND WINTER WEATHER
ADVISORY TO ENCOMPASS REMAINDER OF THE CWA TO COVER BOTH FALLING
THEN EVENTUAL BLOWING SNOW. AT 04Z SURFACE ANALYSIS HAD A 1010MB
LOW NEAR THE SD/IA/NE BORDER...WHICH IS TRACKING A BIT FARTHER
NORTH THAN 12Z/18 GUIDANCE HAD SUGGESTED. STRONGEST 3 HOUR
PRESSURE FALLS WOULD SUGGEST A CONTINUED ESE TRACK TOWARD CENTRAL
ILLINOIS. NUMERICAL GUIDANCE AND EMPIRICAL RULES OF THUMB WOULD
PLACE THE AXIS OF HEAVIEST SNOWFALL RIGHT ACROSS THE SOUTHERN
THIRD OF OUR CWA.

SNOWFALL AMOUNTS WILL BE TRICKY. MOISTURE IS LIMITED AND GARCIA
METHOD WOULD SUGGEST TOTALS OF 2-4" IN THE HEAVIEST BAND...HOWEVER
DEEP LAYER WITH FAVORABLE DENDRITIC TEMPS AND VERY COLD AIRMASS
SHOULD ALLOW FOR A PARTICULARLY DRY AND FLOOFFY SNOW. WOULD
GENERALLY EXPECT SNOW:LIQUID RATIOS QUITE HIGH LIKELY IN THE
20-30:1 NEIGHBORHOOD. GOING FORECAST SNOWFALL TOTALS LOOK RIGHT ON
TARGET AND DIDN`T MAKE ANY CHANGES...WHILE TOTALS WILL PROBABLY
END UP ON THE BOTTOM END OF OR JUST BELOW ADVISORY CRITERIA BITTER
COLD TEMPS SHOULD CAUSE SNOW TO IMMEDIATELY ACCUMULATE ON
ROADWAYS. IN ADDITION...PEAK SNOW INTENSITY WILL LIKELY BE AROUND
MORNING RUSH HOUR LIKELY RESULTING IN VERY DIFFICULT TRAVEL.

ONLY REAL CHANGE TO GOING FORECAST BESIDES HOISTING THE ADVISORY
WAS TO MOVE UP THE END TIME OF THE SNOW TO MIDDAY WEDNESDAY...WITH
THE ONE EXCEPTION BEING NEAR THE LAKE IN NW INDIANA. EASTERLY
WINDS OFF THE LAKE COULD ALLOW FOR SOME SLIGHTLY ENHANCED TOTALS
NEAR THE LAKE IN NE IL...THOUGH FETCH LOOKS SHORT ENOUGH TO NOT BE
A BIG PROBLEM IN ILLINOIS. BY AFTERNOON WINDS TURN MORE NORTHERLY
AND FETCH INCREASES CONSIDERABLY SO WILL PROBABLY SEE LAKE EFFECT
SNOW SHOWERS FOR A TIME IN OUR NW IN COUNTIES...THOUGH EXPECT
DURATION OF THE LAKE EFFECT TO BE SHORT ENOUGH TO PRECLUDE MOST
AREAS FROM EXCEEDING 6 INCHES TOTAL FROM SYNOPTIC/LAKE EVENT.
MAJORITY OF THE LAKE EFFECT SHOULD SHIFT EAST INTO INDIANA
WEDNESDAY EVENING WITH MAIN LINGERING THREAT BEING
BLOWING/DRIFTING IN OPEN/RURAL AREAS WHICH SHOULD ALSO SUBSIDE BY
LATE EVENING AS WINDS DECREASE.

IZZI

&&

.AVIATION...
1040 PM CST

0600 UTC TAFS...CONDITIONS WILL RAPIDLY DETERIORATE SHORTLY WITH
THE APPROACH OF THE NEXT CLIPPER.

LITTLE CHANGE MADE TO THE GOING TAFS WITH THE EXCEPTION OF MOVING
UP THE ONSET OF SNOWFALL BY AN HOUR. LATEST RADAR IMAGERY SHOWS
THE SNOW SPREADING ACROSS THE MISSISSIPPI RIVER INTO NORTHWESTERN
ILLINOIS. STILL EXPECT THE SFC LOW TO QUICKLY DROP SEWD THROUGH
THE UPPER MISSOURI VALLEY WHILE THE SFC RIDGE AXIS MOVES ACROSS
LAKE MICHIGAN AND INDIANA. MID AND HIGH CLOUD HAVE OVERSPREAD THE
TERMINALS WHILE WINDS REMAIN GENERALLY LGT/VRBL AS THE SFC RIDGE
PASSES TO THE EAST. WINDS WILL BEGIN TO INCREASE AND BECOME SELY
AS THE SFC LOW TRACKS INTO NRN MISSOURI. EXPECTS CIGS/VIS TO
QUICKLY DROP THROUGH MVFR TO IFR WITH SNOW MOVING OVER RFD BY 07Z
AND THEN SPREADING EWD TO THE CHICAGO AREA TERMINALS BY 08Z. HAVE
MAINTAINED THE TEMPO GROUP FOR LIFR VIS FOR THE 12-15Z TIME
RANGE...BUT THIS MIGHT BE A LITTLE CONSERVATIVE AS WINDS WILL BE
TURNING NELY FOR A PERIOD UNTIL AT LEAST 18Z AND LAKE ENHANCEMENT
TO THE SNOWFALL MAY EXTEND THE PERIOD OF LIFR VIS.

FOLLOWING THE PASSAGE OF THE SFC LOW TO THE SOUTH AND EAST...WINDS
WILL QUICKLY INCREASE...LEADING TO BLOWING AND DRIFTING OF THE
NEWLY FALLEN SNOW. SINCE TEMPERATURES WILL BE VERY LOW FOR THE
DURATION OF THE SNOWFALL...SNOW TO LIQUID RATIOS WILL BE
HIGH...CREATING A VERY DRY SNOW. HAVE TRENDED VISBY TO IFR FOR THE
WITH BLOWING SNOW. DRIFTING SNOW WILL LIKELY CAUSE DIFFICULTIES
FOR SNOW REMOVAL CREWS.

KREIN

&&

.MARINE...
210 PM CST

WINDS HAVE DIMINISHED ACROSS THE LAKE THIS AFTERNOON AND THEREFORE
HAVE DROPPED THE GALE AND FREEZING SPRAY WARNINGS. WINDS WILL
CONTINUE TO DIMINISH OVERNIGHT AS A RIDGE OF HIGH PRESSURE MOVES
IN ACROSS THE REGION. A LOW PRESSURE SYSTEM WILL DROP DOWN INTO
CENTRAL ILLINOIS WEDNESDAY MORNING AND THEN TRACK EASTWARD THROUGH
THE OHIO RIVER VALLEY INTO THURSDAY MORNING. WINDS WILL BE ON THE
INCREASE THURSDAY MORNING AS THE LOW REACHES THE MID ATLANTIC
COAST AND A STRONG RIDGE OF HIGH PRESSURE MOVES IN ACROSS THE
GREAT LAKES. WILL KEEP THE GALE WATCH GOING FOR THE MOMENT AS
WINDS STILL MAY GUST UP TO GALE FORCE ON THURSDAY.  THIS RIDGE
WILL SLOWLY MOVE OFF TOWARD THE SOUTHEAST US BY SATURDAY AS THE
NEXT SYSTEM TAKES AIM ON THE LAKES.

VISIBLE SATELLITE FROM TODAY REVEALS THAT THERE IS FAIRLY
EXTENSIVE ICE COVER ACROSS THE NEARSHORE ZONES EXCEPT FOR THE
FURTHEST ZONE TO THE EAST FROM BURNS HARBOR TO MICHIGAN CITY.
THEREFORE...WILL BE DROPPING THE MENTION OF WAVES IN THE NEARSHORE
FORECAST.

HALBACH

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-
     ILZ022-ILZ023-ILZ032-ILZ033-ILZ039 UNTIL MIDNIGHT THURSDAY.

     WIND CHILL WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...MIDNIGHT THURSDAY TO NOON
     FRIDAY.

IN...WIND CHILL WATCH...INZ001-INZ002-INZ010-INZ011-INZ019...MIDNIGHT
     THURSDAY TO NOON FRIDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019
     UNTIL MIDNIGHT THURSDAY.

LM...GALE WATCH...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...MIDNIGHT THURSDAY TO 1 PM THURSDAY.

&&

$$


000
FXUS63 KLOT 140416
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1016 PM CST TUE JAN 13 2009

.DISCUSSION...
1017 PM CST

AS MENTIONED IN PREVIOUS AFD DECIDED TO EXPAND WINTER WEATHER
ADVISORY TO ENCOMPASS REMAINDER OF THE CWA TO COVER BOTH FALLING
THEN EVENTUAL BLOWING SNOW. AT 04Z SURFACE ANALYSIS HAD A 1010MB
LOW NEAR THE SD/IA/NE BORDER...WHICH IS TRACKING A BIT FARTHER
NORTH THAN 12Z/18 GUIDANCE HAD SUGGESTED. STRONGEST 3 HOUR
PRESSURE FALLS WOULD SUGGEST A CONTINUED ESE TRACK TOWARD CENTRAL
ILLINOIS. NUMERICAL GUIDANCE AND EMPIRICAL RULES OF THUMB WOULD
PLACE THE AXIS OF HEAVIEST SNOWFALL RIGHT ACROSS THE SOUTHERN
THIRD OF OUR CWA.

SNOWFALL AMOUNTS WILL BE TRICKY. MOISTURE IS LIMITED AND GARCIA
METHOD WOULD SUGGEST TOTALS OF 2-4" IN THE HEAVIEST BAND...HOWEVER
DEEP LAYER WITH FAVORABLE DENDRITIC TEMPS AND VERY COLD AIRMASS
SHOULD ALLOW FOR A PARTICULARLY DRY AND FLOOFFY SNOW. WOULD
GENERALLY EXPECT SNOW:LIQUID RATIOS QUITE HIGH LIKELY IN THE
20-30:1 NEIGHBORHOOD. GOING FORECAST SNOWFALL TOTALS LOOK RIGHT ON
TARGET AND DIDN`T MAKE ANY CHANGES...WHILE TOTALS WILL PROBABLY
END UP ON THE BOTTOM END OF OR JUST BELOW ADVISORY CRITERIA BITTER
COLD TEMPS SHOULD CAUSE SNOW TO IMMEDIATELY ACCUMULATE ON
ROADWAYS. IN ADDITION...PEAK SNOW INTENSITY WILL LIKELY BE AROUND
MORNING RUSH HOUR LIKELY RESULTING IN VERY DIFFICULT TRAVEL.

ONLY REAL CHANGE TO GOING FORECAST BESIDES HOISTING THE ADVISORY
WAS TO MOVE UP THE END TIME OF THE SNOW TO MIDDAY WEDNESDAY...WITH
THE ONE EXCEPTION BEING NEAR THE LAKE IN NW INDIANA. EASTERLY
WINDS OFF THE LAKE COULD ALLOW FOR SOME SLIGHTLY ENHANCED TOTALS
NEAR THE LAKE IN NE IL...THOUGH FETCH LOOKS SHORT ENOUGH TO NOT BE
A BIG PROBLEM IN ILLINOIS. BY AFTERNOON WINDS TURN MORE NORTHERLY
AND FETCH INCREASES CONSIDERABLY SO WILL PROBABLY SEE LAKE EFFECT
SNOW SHOWERS FOR A TIME IN OUR NW IN COUNTIES...THOUGH EXPECT
DURATION OF THE LAKE EFFECT TO BE SHORT ENOUGH TO PRECLUDE MOST
AREAS FROM EXCEEDING 6 INCHES TOTAL FROM SYNOPTIC/LAKE EVENT.
MAJORITY OF THE LAKE EFFECT SHOULD SHIFT EAST INTO INDIANA
WEDNESDAY EVENING WITH MAIN LINGERING THREAT BEING
BLOWING/DRIFTING IN OPEN/RURAL AREAS WHICH SHOULD ALSO SUBSIDE BY
LATE EVENING AS WINDS DECREASE.

IZZI

&&

.AVIATION...
600 PM CST

0000 UTC TAFS...WEATHER WILL START OUT QUIET FOR AVIATION
CONCERNS...BUT CONDITIONS WILL RAPIDLY DETERIORATE WITH THE
APPROACH OF THE NEXT CLIPPER.

AT ISSUANCE TIME...THE SFC LOW IS QUICKLY DROPPING SEWD THROUGH SOUTH
DAKOTA WHILE THE SFC RIDGE AXIS MOVES ACROSS ILLINOIS. SKIES WILL
START OUT SKC WITH RELATIVELY LIGHT WINDS...BUT MID AND HIGH CLOUD
WILL OVERSPREAD THE TERMINALS WITHIN A FEW HOURS. WINDS WILL
REMAIN LGT/VRBL WITH THE PASSAGE OF THE SFC RIDGE AND THEN
INCREASE AND BECOME SELY AS THE SFC LOW TRACKS ALONG THE MISSOURI
RIVER TONIGHT AND INTO NRN MISSOURI BY ARND 12Z. EXPECTS CIGS/VIS
TO QUICKLY DROP THROUGH MVFR TO IFR WITH SNOW MOVING OVER RFD BY
06Z AND THEN SPREADING EWD TO THE CHICAGO AREA TERMINALS BY 09Z.
HAVE MAINTAINED THE TEMPO GROUP FOR LIFR VIS FOR THE 12-15Z TIME
RANGE...BUT THIS MIGHT BE A LITTLE TOO CONSERVATIVE AS WINDS WILL
BE TURNING NELY FOR A PERIOD UNTIL AT LEAST 18Z AND LAKE
ENHANCEMENT TO THE SNOWFALL MAY EXTEND THE PERIOD OF LIFR VIS.

FOLLOWING THE PASSAGE OF THE SFC LOW TO THE SOUTH AND EAST...WINDS
WILL QUICKLY INCREASE...LEADING TO BLOWING AND DRIFTING OF THE
NEWLY FALLEN SNOW. SINCE TEMPERATURES WILL BE VERY LOW FOR THE
DURATION OF THE SNOWFALL...SNOW TO LIQUID RATIOS WILL BE
HIGH...CREATING A VERY DRY SNOW. HAVE TRENDED VISBY TO IFR FOR THE
24-30 HOUR PERIOD AT ORD WITH BLOWING SNOW. DRIFTING SNOW WILL
LIKELY CAUSE DIFFICULTIES FOR SNOW REMOVAL CREWS.

KREIN

&&

.MARINE...
210 PM CST

WINDS HAVE DIMINISHED ACROSS THE LAKE THIS AFTERNOON AND THEREFORE
HAVE DROPPED THE GALE AND FREEZING SPRAY WARNINGS. WINDS WILL
CONTINUE TO DIMINISH OVERNIGHT AS A RIDGE OF HIGH PRESSURE MOVES
IN ACROSS THE REGION. A LOW PRESSURE SYSTEM WILL DROP DOWN INTO
CENTRAL ILLINOIS WEDNESDAY MORNING AND THEN TRACK EASTWARD THROUGH
THE OHIO RIVER VALLEY INTO THURSDAY MORNING. WINDS WILL BE ON THE
INCREASE THURSDAY MORNING AS THE LOW REACHES THE MID ATLANTIC
COAST AND A STRONG RIDGE OF HIGH PRESSURE MOVES IN ACROSS THE
GREAT LAKES. WILL KEEP THE GALE WATCH GOING FOR THE MOMENT AS
WINDS STILL MAY GUST UP TO GALE FORCE ON THURSDAY.  THIS RIDGE
WILL SLOWLY MOVE OFF TOWARD THE SOUTHEAST US BY SATURDAY AS THE
NEXT SYSTEM TAKES AIM ON THE LAKES.

VISIBLE SATELLITE FROM TODAY REVEALS THAT THERE IS FAIRLY
EXTENSIVE ICE COVER ACROSS THE NEARSHORE ZONES EXCEPT FOR THE
FURTHEST ZONE TO THE EAST FROM BURNS HARBOR TO MICHIGAN CITY.
THEREFORE...WILL BE DROPPING THE MENTION OF WAVES IN THE NEARSHORE
FORECAST.

HALBACH

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-
     ILZ022-ILZ023-ILZ032-ILZ033-ILZ039 UNTIL MIDNIGHT THURSDAY.

     WIND CHILL WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...MIDNIGHT THURSDAY TO NOON
     FRIDAY.

IN...WIND CHILL WATCH...INZ001-INZ002-INZ010-INZ011-INZ019...MIDNIGHT
     THURSDAY TO NOON FRIDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019
     UNTIL MIDNIGHT THURSDAY.

LM...GALE WATCH...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...MIDNIGHT THURSDAY TO 1 PM THURSDAY.

&&

$$


000
FXUS63 KILX 140258
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
858 PM CST TUE JAN 13 2009

.DISCUSSION...
ISSUED 858 PM CST TUE JAN 13 2009

SNOW IS SPREADING INTO CENTRAL IL PRETTY MUCH AS EXPECTED. THE
LATEST MODEL RUNS SHOW THE CLIPPER IS EXPECTED TO FOLLOW A
SLIGHTLY FARTHER SOUTH TRACK THAN THE 12Z MODELS SHOWED. THE
HEAVIER SNOW BAND MAY EXTEND A LITTLE FARTHER SOUTH OF
I-74...POSSIBLY AS FAR SOUTH AS LINCOLN. THE 02Z RUC IS SHOWING
THIS TREND...AS WELL AS THE 18Z GFS. THE 00Z NAM IS IN...AND SHOWS
THE HEAVY AXIS ALONG I-74...NOT NORTH OF I-74. THERE ARE EVEN
INDICATIONS OF A FEW LOCATIONS GETTING NEAR THE 6 INCH MARK. THE
COLD AIR AND FLUFFY NATURE OF THE SNOW WILL ALLOW THE SNOW TO PILE
UP QUICKLY. WILL KEEP THE ADVISORY GOING INSTEAD OF A
WARNING...AS THE MAJORITY OF THE AREA SHOULD REMAIN LESS THAN 6
INCHES. EVEN WITH SLIGHTLY HIGHER SNOW TOTALS... MOST AREAS NORTH
OF LINCOLN WILL BE IN THE 3 TO 5 INCH RANGE ON THE HIGH SIDE.

BLOWING ON WEDNESDAY WILL MAKE MEASURING THE SNOW QUITE DIFFICULT.
DRIFTS AND REDUCED VISIBILITY IN THE BLOWING SNOW WILL MAKE TRAVEL
QUITE DIFFICULT ON WEDNESDAY...ESPECIALLY ON NORTH-SOUTH ROADS.
ACTUALLY...WINDS WILL BE NW...SO EVEN EAST-WEST ROADS WILL SEE
PLENTY OF DRIFTING.

I BUMPED UP THE SNOW TOTALS IN THE GRIDS TO ACCOUNT FOR RAPID SNOW
ACCUMS BETWEEN 3 AM AND 8 AM.

LOW TEMPS HAVE ALREADY BEEN REACHED...AND SOUTHERLY FLOW AND
INCREASING CLOUDS HAS TURNED TEMP TRENDS WARMER. THAT WILL
CONTINUE THE REST OF THE NIGHT...STEADY OR SLOWLY RISING TEMPS.

SNOW WILL CONTINUE WED MORNING IN THE NE THIRD OF THE CWA...WITH
ACCUMULATIONS CONTINUING UNTIL LATE MORNING. A VERY BLUSTERY DAY
IS IN STORE FOR WED.

UPDATED GRIDS AND ZONES WILL BE AVAILABLE SHORTLY.

SHIMON
&&

.AVIATION...
ISSUED 554 PM CST TUE JAN 13 2009...FOR THE 00Z TAFS

THE CLIPPER IS ON TRACK TO PUT DOWN 2 TO 4 INCHES OF SNOW ACROSS
THE AREA. PIA AND BMI WILL GET HIT FIRST...WITH CIGS AND VIS DOWN
TO IFR AROUND MIDNIGHT. SPI/DEC/CMI WILL BE ABOUT 2-4 HOURS BEHIND
THEM FOR SIMILAR CONDITIONS.

THE LATEST MODEL GUIDANCE IS SHOWING A SLIGHTLY FARTHER SOUTH
TRACK FOR THE LOW CENTER...WHICH WILL PUT MEASURABLE SNOW A BIT
FARTHER SOUTH AS WELL. WILL KEEP SOME LIFR VIS AT ALL TAF
SITES...WITH VLIFR POSSIBLE IN PIA AND BMI FOR THE 11Z TO 14Z TIME
FRAME.

WINDS WILL REMAIN SOUTHEAST AT 10 TO 15 KTS UNTIL MID
MORNING...THEN WILL CHANGE OVER TO NORTHWEST AND INCREASE TO 15-20
SUSTAINED AND GUSTS TO 30KTS BY AFTERNOON. CIGS WILL RISE AS
SUBSIDENCE AND DRY AIR BEHIND THE FRONT SHUT DOWN THE SNOW BY MID
DAY...BUT BLOWING SNOW WILL LIKELY PUT VIS READINGS CLOSE TO
IFR...IF NOT LIFR OR EVEN VLIFR VIS AT TIMES IN PIA AND BMI. WHITE
OUT CONDITIONS CAN NOT BE RULED OUT IF THE WINDS GET UP TO 30 KTS
AND BLOW THE FLUFFY SNOW.

WINDS WILL CONTINUE UNTIL AT LEAST 00Z TOMORROW EVENING...SO BLSN
MAY BE AN ISSUE INTO WED EVENING WHERE THE HIGHER SNOWFALL DEVELOPS.

SHIMON
&&

.PREV DISCUSSION...
ISSUED 334 PM CST TUE JAN 13 2009

LATEST SURFACE ANALYSIS HAD A SKINNY RIDGE OF HIGH PRESSURE
EXTENDING FROM THE SOUTHERN PLAINS INTO THE UPPER MIDWEST. FURTHER
UPSTREAM...THE LATEST IN OUR RECENT SERIES OF CLIPPER SYSTEMS WAS
OVER THE NORTHERN HIGH PLAINS. THE SNOW CHANCES/AMOUNTS WITH THE
APPROACHING CLIPPER LATE TONIGHT INTO WEDNESDAY...AS WELL AS HOW
COLD IT WILL BE IN THE WAKE OF THE SYSTEM OVER THE NEXT COUPLE OF
DAYS ARE THE PRIMARY FORECAST CONCERNS THIS AFTERNOON.

12Z MODELS IN GOOD OVERALL AGREEMENT WITH THE CLIPPER SYSTEM...
THOUGH THERE ARE SUBTLE DIFFERENCES IN THE TRACK OF THE STORM. STILL
PREFER THE SOUTHERN MOST TRACK OF THE GFS...GIVEN THE DIGGING NATURE
OF THE MEAN UPPER TROF...WHICH WOULD SUPPORT THE HEAVIEST SNOWFALL
ALONG AND NORTH OF THE I-74 CORRIDOR. GUIDANCE TEMPERATURES STILL
SHOWING SOME SPREAD...LIKELY A RESULT OF THE STORM TRACK DIFFERENCES
AND RESULTING DIFFERENCES IN SNOWFALL. WILL TEND TO FOLLOW A BLEND
OF MODEL TEMPERATURES GIVEN LINGERING UNCERTAINTY.

SHORT TERM...TONIGHT THROUGH FRIDAY...

TONIGHT AND WEDNESDAY...CLIPPER WILL RAPIDLY DIVE SOUTHEAST
TONIGHT...LIKELY REACHING WEST CENTRAL ILLINOIS BY 12Z WEDNESDAY.
THE SYSTEM WILL CONTINUE EAST TO SOUTHERN OHIO BY 00Z THURSDAY.
STRONG WAA/ISENTROPIC LIFT AND THE CORRESPONDING LOW CONDENSATION
PRESSURE DEFICITS SUPPORT SNOW BREAKING OUT FROM NORTHWEST TO
SOUTHEAST ACROSS THE FORECAST AREA OVERNIGHT...LINGERING INTO EARLY
WEDNESDAY AS THE UPPER WAVE/JET MOVE THROUGH. THE FORCING
OVERNIGHT IS QUITE STRONG...BUT THE PERIOD OF STRONG FORCING IS
BRIEF AND THE AVAILABLE MOISTURE LIMITED. STILL...THE HIGH SNOW TO
WATER RATIO EXPECTED DUE TO THE COLD AIRMASS SUPPORTS A BAND OF
2-4 INCH SNOWS...PRIMARILY ALONG AND NORTH OF THE I-74 CORRIDOR.
LOWER SNOW TOTALS ARE EXPECTED AS YOU HEAD SOUTH FROM I-74. THERE
IS NOT A STRONG SIGNAL OF A GOOD DEFORMATION SNOW BAND ON THE BACK
SIDE OF THE CLIPPER...SO EXPECT SNOWS TO TAPER OFF PRETTY QUICKLY
WEDNESDAY. HOWEVER...AS WINDS PICK UP ON THE BACK SIDE OF THE
CLIPPER SYSTEM...WITH WIND GUSTS OVER 30 MPH...BLOWING AND
DRIFTING SNOW WILL DEVELOP ACROSS AREAS THAT RECEIVED ACCUMULATING
SNOW. THE COMBINATION OF ACCUMULATING AND BLOWING SNOW ACROSS
NORTHERN SECTIONS OF THE FORECAST AREA WILL MAKE TRAVEL TRICKY.
SO...HAVE ISSUED A WINTER WEATHER ADVISORY IN NORTHERN SECTIONS OF
THE FORECAST AREA OVERNIGHT AND WEDNESDAY.

WEDNESDAY NIGHT THROUGH FRIDAY...COLD AIR WILL CONTINUE TO SURGE
INTO THE REGION INTO AT LEAST THURSDAY NIGHT ON NORTHWEST WINDS AS
AN ARCTIC HIGH BUILDS THROUGH ILLINOIS. THIS COLD AIR WILL BE
ENHANCED ACROSS THE NORTHERN SECTIONS OF THE FORECAST AREA WHERE
SNOW COVER WILL EXIST. THIS COLD AIR WILL RESULT IN TWO NIGHTS OF
NEAR OR SUB ZERO LOWS WEDNESDAY NIGHT AND THURSDAY NIGHT AND A DAY
OF SINGLE DIGIT HIGHS ON THURSDAY. THESE BITTERLY COLD TEMPERATURES
WILL COMBINE WITH THE WIND TO PRODUCE WIND CHILL VALUES OF -15F OR
COLDER FOR MUCH OF THE PERIOD. HAVE DECIDED TO ISSUE A WIND CHILL
ADVISORY FROM 06Z THURSDAY-18Z FRIDAY FOR AREAS NORTH OF I-70 TO
ACCOUNT FOR THE BITTERLY COLD CONDITIONS. WHILE AREAS SOUTH OF I-70
SHOULD REMAIN ABOVE ADVISORY CRITERIA DUE TO SLIGHTLY WARMER
TEMPERATURES AND LITTLE/NO SNOW COVER...IT WILL STILL BE QUITE COLD
THERE TOO.

TEMPERATURES WILL BEGIN TO MODERATE SOME ON FRIDAY AS THE ARCTIC
HIGH SHIFTS EAST AND WINDS BEGIN TO TURN TO THE SOUTHWEST.

LONG TERM...SATURDAY THROUGH TUESDAY...MODELS/ENSEMBLES REMAIN IN
REASONABLE AGREEMENT WITH THE MEAN FLOW PATTERN THROUGH MUCH OF THE
EXTENDED FORECAST PERIOD...WITH A RIDGE WEST/TROF EAST CONFIGURATION
ACROSS NORTH AMERICA. HOWEVER...THE AGREEMENT WITH RESPECT TO THE
SMALLER SCALE WAVES DIVING INTO THE MEAN TROF IS STILL NOT VERY GOOD
AND GETS INCREASINGLY POOR WITH TIME. THE CORE OF THE COLDEST AIR
WITHIN THE MEAN EASTERN NORTH AMERICAN TROF IS STILL EXPECTED TO
RETREAT TO NEW ENGLAND AND EASTERN CANADA THROUGH THE PERIOD AND
THIS WILL RESULT IN A MODERATION OF TEMPERATURES. AS IN RECENT
DAYS...WILL NOT HAVE ANY MENTION OF PRECIPITATION AT THIS TIME.
WHILE SEVERAL SHORT WAVE IMPULSES ARE EXPECTED TO DIVE INTO THE MEAN
UPPER TROF DURING THE PERIOD...THESE IMPULSES WILL BE MOISTURE
STARVED AND NO STRONG MODEL CONSENSUS EXISTS ON THEIR TIMING OR
TRACK. HOWEVER...THE TRACK PREDICTED BY A BULK OF THE SOLUTIONS
SUGGESTS MOST OF THE PRECIPITATION SHOULD STAY TO OUR NORTH AND
EAST. THE MODELS ARE SIGNALING A TRANSITION TO A MORE ZONAL FLOW
PATTERN JUST BEYOND THIS FORECAST PERIOD...BUT ARE CURRENTLY ALL
OVER THE PLACE IN HOW WE WILL GET THERE. STAY TUNED.

BAK

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM CST
WEDNESDAY FOR ILZ027>031-036>038-040>046.

WIND CHILL ADVISORY FROM MIDNIGHT WEDNESDAY NIGHT TO 12 PM CST
FRIDAY FOR ILZ027>031-036>038-040>057-061.

&&

$$


000
FXUS63 KLOT 140238
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
838 PM CST TUE JAN 13 2009

.DISCUSSION...
838 PM CST

WSW TO EXPAND WINTER WX ADVISORY TO ENCOMPASS THE REMAINDER OF THE
CWA WILL BE ISSUED BY 9 PM. WHILE SNOWFALL AMOUNTS ALONE MAY FALL
SHY OF CRITERIA...THERE IS A REASONABLY GOOD CHANCE THAT WE WILL
EVENTUALLY NEED AN ADVISORY FOR BLOWING SNOW IN OUTLYING AREAS BY
LATE AFTERNOON SO GIVEN THAT SNOW WILL FALL QUITE STOUTLY FOR
SEVERAL HOURS LATE TONIGHT/WEDNESDAY MORNING FEEL THE COURSE OF
LEAST REGRET IS TO EXPAND THE ADVISORY TO HEIGHTEN AWARENESS OF
THE IMPENDING SNOW AND BLOWING SNOW EVENT.

IZZI

&&

.PREV DISCUSSION...
607 PM CST

HAVE FIRED OFF AN UPDATE TO FIRST PERIOD TO LOWER TEMPS THIS
EVENING AND TO TWEAK HOURLY TEMP GRIDS TO REFLECT A FAIRLY STOUT
RISE OVERNIGHT. A SHORT WINDOW OF CLEAR SKIES AND NEARLY CALM
WINDS EARLY THIS EVENING HAS ALREADY ALLOWED FOR A RAPID DROP IN
TEMPS AND THIS TREND EXPECTED TO CONTINUE UNTIL HIGH CLOUDINESS
RAPIDLY OVERSPREADS THE AREA IN ADVANCE THE FAST MOVING CLIPPER.
ONCE HIGH CLOUDS ARRIVE TEMPS SHOULD LEVEL OFF...THEN EVENTUALLY
RISE OVERNIGHT AS CLOUDINESS THICKENS AND WINDS TURN
SOUTHEASTERLY.

MAY ALSO NEED TO CONSIDER EXPANDING GOING ADVISORY FARTHER
NORTHWARD WITH A MID-EVENING FORECAST UPDATE. COMBINATION OF
FALLING THEN BLOWING SNOW MAY END UP BECOMING A PROBLEM FARTHER
NORTH THAN CURRENT HEADLINES SUGGEST...BUT WOULD LIKE TO WAIT TO
GET A GANDER AT 00Z GUIDANCE BEFORE MAKING ANY DRAMATIC
ADJUSTMENTS.

IZZI

&&

.AVIATION...
600 PM CST

0000 UTC TAFS...WEATHER WILL START OUT QUIET FOR AVIATION
CONCERNS...BUT CONDITIONS WILL RAPIDLY DETERIORATE WITH THE
APPROACH OF THE NEXT CLIPPER.

AT ISSUANCE TIME...THE SFC LOW IS QUICKLY DROPPING SEWD THROUGH SOUTH
DAKOTA WHILE THE SFC RIDGE AXIS MOVES ACROSS ILLINOIS. SKIES WILL
START OUT SKC WITH RELATIVELY LIGHT WINDS...BUT MID AND HIGH CLOUD
WILL OVERSPREAD THE TERMINALS WITHIN A FEW HOURS. WINDS WILL
REMAIN LGT/VRBL WITH THE PASSAGE OF THE SFC RIDGE AND THEN
INCREASE AND BECOME SELY AS THE SFC LOW TRACKS ALONG THE MISSOURI
RIVER TONIGHT AND INTO NRN MISSOURI BY ARND 12Z. EXPECTS CIGS/VIS
TO QUICKLY DROP THROUGH MVFR TO IFR WITH SNOW MOVING OVER RFD BY
06Z AND THEN SPREADING EWD TO THE CHICAGO AREA TERMINALS BY 09Z.
HAVE MAINTAINED THE TEMPO GROUP FOR LIFR VIS FOR THE 12-15Z TIME
RANGE...BUT THIS MIGHT BE A LITTLE TOO CONSERVATIVE AS WINDS WILL
BE TURNING NELY FOR A PERIOD UNTIL AT LEAST 18Z AND LAKE
ENHANCEMENT TO THE SNOWFALL MAY EXTEND THE PERIOD OF LIFR VIS.

FOLLOWING THE PASSAGE OF THE SFC LOW TO THE SOUTH AND EAST...WINDS
WILL QUICKLY INCREASE...LEADING TO BLOWING AND DRIFTING OF THE
NEWLY FALLEN SNOW. SINCE TEMPERATURES WILL BE VERY LOW FOR THE
DURATION OF THE SNOWFALL...SNOW TO LIQUID RATIOS WILL BE
HIGH...CREATING A VERY DRY SNOW. HAVE TRENDED VISBY TO IFR FOR THE
24-30 HOUR PERIOD AT ORD WITH BLOWING SNOW. DRIFTING SNOW WILL
LIKELY CAUSE DIFFICULTIES FOR SNOW REMOVAL CREWS.

KREIN

&&

.MARINE...
210 PM CST

WINDS HAVE DIMINISHED ACROSS THE LAKE THIS AFTERNOON AND THEREFORE
HAVE DROPPED THE GALE AND FREEZING SPRAY WARNINGS. WINDS WILL
CONTINUE TO DIMINISH OVERNIGHT AS A RIDGE OF HIGH PRESSURE MOVES
IN ACROSS THE REGION. A LOW PRESSURE SYSTEM WILL DROP DOWN INTO
CENTRAL ILLINOIS WEDNESDAY MORNING AND THEN TRACK EASTWARD THROUGH
THE OHIO RIVER VALLEY INTO THURSDAY MORNING. WINDS WILL BE ON THE
INCREASE THURSDAY MORNING AS THE LOW REACHES THE MID ATLANTIC
COAST AND A STRONG RIDGE OF HIGH PRESSURE MOVES IN ACROSS THE
GREAT LAKES. WILL KEEP THE GALE WATCH GOING FOR THE MOMENT AS
WINDS STILL MAY GUST UP TO GALE FORCE ON THURSDAY.  THIS RIDGE
WILL SLOWLY MOVE OFF TOWARD THE SOUTHEAST US BY SATURDAY AS THE
NEXT SYSTEM TAKES AIM ON THE LAKES.

VISIBLE SATELLITE FROM TODAY REVEALS THAT THERE IS FAIRLY
EXTENSIVE ICE COVER ACROSS THE NEARSHORE ZONES EXCEPT FOR THE
FURTHEST ZONE TO THE EAST FROM BURNS HARBOR TO MICHIGAN CITY.
THEREFORE...WILL BE DROPPING THE MENTION OF WAVES IN THE NEARSHORE
FORECAST.

HALBACH

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ010-ILZ019-ILZ021-ILZ032-ILZ033-
     ILZ039...MIDNIGHT WEDNESDAY TO 6 PM WEDNESDAY.

     WIND CHILL WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...9 PM WEDNESDAY TO NOON FRIDAY.

IN...WIND CHILL WATCH...INZ001-INZ002-INZ010-INZ011-INZ019...9 PM
     WEDNESDAY TO NOON FRIDAY.

     WINTER WEATHER ADVISORY...INZ019...MIDNIGHT WEDNESDAY TO 6 PM
     WEDNESDAY.

LM...GALE WATCH...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 PM WEDNESDAY TO 1 PM THURSDAY.

&&

$$


000
FXUS63 KLOT 140007
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
607 PM CST TUE JAN 13 2009

.DISCUSSION...
607 PM CST

HAVE FIRED OFF AN UPDATE TO FIRST PERIOD TO LOWER TEMPS THIS
EVENING AND TO TWEAK HOURLY TEMP GRIDS TO REFLECT A FAIRLY STOUT
RISE OVERNIGHT. A SHORT WINDOW OF CLEAR SKIES AND NEARLY CALM
WINDS EARLY THIS EVENING HAS ALREADY ALLOWED FOR A RAPID DROP IN
TEMPS AND THIS TREND EXPECTED TO CONTINUE UNTIL HIGH CLOUDINESS
RAPIDLY OVERSPREADS THE AREA IN ADVANCE THE FAST MOVING CLIPPER.
ONCE HIGH CLOUDS ARRIVE TEMPS SHOULD LEVEL OFF...THEN EVENTUALLY
RISE OVERNIGHT AS CLOUDINESS THICKENS AND WINDS TURN
SOUTHEASTERLY.

MAY ALSO NEED TO CONSIDER EXPANDING GOING ADVISORY FARTHER
NORTHWARD WITH A MID-EVENING FORECAST UPDATE. COMBINATION OF
FALLING THEN BLOWING SNOW MAY END UP BECOMING A PROBLEM FARTHER
NORTH THAN CURRENT HEADLINES SUGGEST...BUT WOULD LIKE TO WAIT TO
GET A GANDER AT 00Z GUIDANCE BEFORE MAKING ANY DRAMATIC
ADJUSTMENTS.

IZZI

&&

.PREV DISCUSSION...
338 PM CST

ANOTHER CLIPPER SYSTEM DIVING DOWN FROM THE DAKOTAS TONIGHT IS THE
MAIN FOCUS AS MENTIONED IN PREVIOUS DISCUSSIONS. THIS ONE HOWEVER IS
TAKING A MORE SOUTHERLY TRACK AND FOCUSING HIER QPF AND SNOWFALL
TOTALS SOUTH OF I-80. GENERALLY LOOKING FOR 2-4 INCHES FROM STERLING
DOWN THRU PAXTON OVERNIGHT WITH 1-3 INCHES NORTH AND EAST OF
THERE...THEN DROPPING ANOTHER INCH OR TWO ACROSS NRN IL AND INDIANA
ON WEDNESDAY. A STRONG PRESSURE GRADIENT BEHIND THIS PASSING SYSTEM
ON WEDNESDAY WILL GUST WINDS TO 30 TO 35 MPH AND DRAW COLD ARCTIC
AIR INTO THE REGION. SOME BLOWING AND DRIFTING IS LIKELY WITH THIS
STRONG FLOW GENERALLY AFTER THE SNOW ENDS OR TAPERS TO LITE SNOW
SHOWERS. THE ONLY EXCEPTION WILL BE LAKE EFFECT SNOWS INTO NORTHEAST
IL AND NW INDY WEDNESDAY EVENING. WITH H8 TEMPS DOWN INTO THE LOWER
AND MID 20S...CAPES TO 500 JOULES IS EASILY ACCOMPLISHED. THE ISSUE
FOR WED NGT IS THE TRAJECTORY...PORTRAYED DIFFERENTLY ON WHICH MODEL
YOU CHOOSE. EVEN WITH THE WORST... WINDS TEND TO BACK TO THE NW LATE
WED EVENING TO DIRECT ANYMORE LAKE EFFECT INTO SW MICHIGAN.

HAVE DECIDED TO GO WITH AN ADVISORY IN SW SECTIONS. ACCUMULATIONS UP
TO 6 INCHES MAY BE PSBL THERE BETWEEN TNGT AND WED. BUT MAIN
EMPHASIS IS ON STRONG WINDS AND SUBZERO TEMPS THAT HAVE BEEN
ADVERTISED. WIND CHILLS OF -20 COME QUICK AFTER NIGHTFALL WED
EVENING AND PLUMMET TO -30 BEFORE SUNRISE THURSDAY. WIND CHILLS
RECOVER DURING THE DAY THURSDAY ABOVE -30 BUT DROP AGAIN THURSDAY
NIGHT INTO FRIDAY MORNING TO 30 BELOW OR LOWER. THUS HAVE A WIND
CHILL WATCH OUT STARTING WED NGT. MODELS HAVE BEEN IMPULSIVE OF LATE
WITH GENERATING STRONG WINDS...SO FURTHER RUNS MAY REDUCE THE
WARNING THREAT TO ADVISORY THREAT OF -20 TO -30.

WITH THE COLD AIR SETTLING IN FOR A WHILE...THE NEXT WARMUP FRIDAY
WILL HERALD THE NEXT CLIPPER DIVING DOWN FROM CANADA AND ANOTHER
BOUT OF SNOW.

RLB

&&

.AVIATION...
600 PM CST

0000 UTC TAFS...WEATHER WILL START OUT QUIET FOR AVIATION
CONCERNS...BUT CONDITIONS WILL RAPIDLY DETERIORATE WITH THE
APPROACH OF THE NEXT CLIPPER.

AT ISSUANCE TIME...THE SFC LOW IS QUICKLY DROPPING SEWD THROUGH SOUTH
DAKOTA WHILE THE SFC RIDGE AXIS MOVES ACROSS ILLINOIS. SKIES WILL
START OUT SKC WITH RELATIVELY LIGHT WINDS...BUT MID AND HIGH CLOUD
WILL OVERSPREAD THE TERMINALS WITHIN A FEW HOURS. WINDS WILL
REMAIN LGT/VRBL WITH THE PASSAGE OF THE SFC RIDGE AND THEN
INCREASE AND BECOME SELY AS THE SFC LOW TRACKS ALONG THE MISSOURI
RIVER TONIGHT AND INTO NRN MISSOURI BY ARND 12Z. EXPECTS CIGS/VIS
TO QUICKLY DROP THROUGH MVFR TO IFR WITH SNOW MOVING OVER RFD BY
06Z AND THEN SPREADING EWD TO THE CHICAGO AREA TERMINALS BY 09Z.
HAVE MAINTAINED THE TEMPO GROUP FOR LIFR VIS FOR THE 12-15Z TIME
RANGE...BUT THIS MIGHT BE A LITTLE TOO CONSERVATIVE AS WINDS WILL
BE TURNING NELY FOR A PERIOD UNTIL AT LEAST 18Z AND LAKE
ENHANCEMENT TO THE SNOWFALL MAY EXTEND THE PERIOD OF LIFR VIS.

FOLLOWING THE PASSAGE OF THE SFC LOW TO THE SOUTH AND EAST...WINDS
WILL QUICKLY INCREASE...LEADING TO BLOWING AND DRIFTING OF THE
NEWLY FALLEN SNOW. SINCE TEMPERATURES WILL BE VERY LOW FOR THE
DURATION OF THE SNOWFALL...SNOW TO LIQUID RATIOS WILL BE
HIGH...CREATING A VERY DRY SNOW. HAVE TRENDED VISBY TO IFR FOR THE
24-30 HOUR PERIOD AT ORD WITH BLOWING SNOW. DRIFTING SNOW WILL
LIKELY CAUSE DIFFICULTIES FOR SNOW REMOVAL CREWS.

KREIN

&&

.MARINE...
210 PM CST

WINDS HAVE DIMINISHED ACROSS THE LAKE THIS AFTERNOON AND THEREFORE
HAVE DROPPED THE GALE AND FREEZING SPRAY WARNINGS. WINDS WILL
CONTINUE TO DIMINISH OVERNIGHT AS A RIDGE OF HIGH PRESSURE MOVES
IN ACROSS THE REGION. A LOW PRESSURE SYSTEM WILL DROP DOWN INTO
CENTRAL ILLINOIS WEDNESDAY MORNING AND THEN TRACK EASTWARD THROUGH
THE OHIO RIVER VALLEY INTO THURSDAY MORNING. WINDS WILL BE ON THE
INCREASE THURSDAY MORNING AS THE LOW REACHES THE MID ATLANTIC
COAST AND A STRONG RIDGE OF HIGH PRESSURE MOVES IN ACROSS THE
GREAT LAKES. WILL KEEP THE GALE WATCH GOING FOR THE MOMENT AS
WINDS STILL MAY GUST UP TO GALE FORCE ON THURSDAY.  THIS RIDGE
WILL SLOWLY MOVE OFF TOWARD THE SOUTHEAST US BY SATURDAY AS THE
NEXT SYSTEM TAKES AIM ON THE LAKES.

VISIBLE SATELLITE FROM TODAY REVEALS THAT THERE IS FAIRLY
EXTENSIVE ICE COVER ACROSS THE NEARSHORE ZONES EXCEPT FOR THE
FURTHEST ZONE TO THE EAST FROM BURNS HARBOR TO MICHIGAN CITY.
THEREFORE...WILL BE DROPPING THE MENTION OF WAVES IN THE NEARSHORE
FORECAST.

HALBACH

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ010-ILZ019-ILZ021-ILZ032-ILZ033-
     ILZ039...MIDNIGHT WEDNESDAY TO 6 PM WEDNESDAY.

     WIND CHILL WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...9 PM WEDNESDAY TO NOON FRIDAY.

IN...WIND CHILL WATCH...INZ001-INZ002-INZ010-INZ011-INZ019...9 PM
     WEDNESDAY TO NOON FRIDAY.

     WINTER WEATHER ADVISORY...INZ019...MIDNIGHT WEDNESDAY TO 6 PM
     WEDNESDAY.

LM...GALE WATCH...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 PM WEDNESDAY TO 1 PM THURSDAY.

&&

$$


000
FXUS63 KLOT 132357
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
557 PM CST TUE JAN 13 2009

.DISCUSSION...
338 PM CST

ANOTHER CLIPPER SYSTEM DIVING DOWN FROM THE DAKOTAS TONIGHT IS THE
MAIN FOCUS AS MENTIONED IN PREVIOUS DISCUSSIONS. THIS ONE HOWEVER IS
TAKING A MORE SOUTHERLY TRACK AND FOCUSING HIER QPF AND SNOWFALL
TOTALS SOUTH OF I-80. GENERALLY LOOKING FOR 2-4 INCHES FROM STERLING
DOWN THRU PAXTON OVERNIGHT WITH 1-3 INCHES NORTH AND EAST OF
THERE...THEN DROPPING ANOTHER INCH OR TWO ACROSS NRN IL AND INDIANA
ON WEDNESDAY. A STRONG PRESSURE GRADIENT BEHIND THIS PASSING SYSTEM
ON WEDNESDAY WILL GUST WINDS TO 30 TO 35 MPH AND DRAW COLD ARCTIC
AIR INTO THE REGION. SOME BLOWING AND DRIFTING IS LIKELY WITH THIS
STRONG FLOW GENERALLY AFTER THE SNOW ENDS OR TAPERS TO LITE SNOW
SHOWERS. THE ONLY EXCEPTION WILL BE LAKE EFFECT SNOWS INTO NORTHEAST
IL AND NW INDY WEDNESDAY EVENING. WITH H8 TEMPS DOWN INTO THE LOWER
AND MID 20S...CAPES TO 500 JOULES IS EASILY ACCOMPLISHED. THE ISSUE
FOR WED NGT IS THE TRAJECTORY...PORTRAYED DIFFERENTLY ON WHICH MODEL
YOU CHOOSE. EVEN WITH THE WORST... WINDS TEND TO BACK TO THE NW LATE
WED EVENING TO DIRECT ANYMORE LAKE EFFECT INTO SW MICHIGAN.

HAVE DECIDED TO GO WITH AN ADVISORY IN SW SECTIONS. ACCUMULATIONS UP
TO 6 INCHES MAY BE PSBL THERE BETWEEN TNGT AND WED. BUT MAIN
EMPHASIS IS ON STRONG WINDS AND SUBZERO TEMPS THAT HAVE BEEN
ADVERTISED. WIND CHILLS OF -20 COME QUICK AFTER NIGHTFALL WED
EVENING AND PLUMMET TO -30 BEFORE SUNRISE THURSDAY. WIND CHILLS
RECOVER DURING THE DAY THURSDAY ABOVE -30 BUT DROP AGAIN THURSDAY
NIGHT INTO FRIDAY MORNING TO 30 BELOW OR LOWER. THUS HAVE A WIND
CHILL WATCH OUT STARTING WED NGT. MODELS HAVE BEEN IMPULSIVE OF LATE
WITH GENERATING STRONG WINDS...SO FURTHER RUNS MAY REDUCE THE
WARNING THREAT TO ADVISORY THREAT OF -20 TO -30.

WITH THE COLD AIR SETTLING IN FOR A WHILE...THE NEXT WARMUP FRIDAY
WILL HERALD THE NEXT CLIPPER DIVING DOWN FROM CANADA AND ANOTHER
BOUT OF SNOW.

RLB

&&

.AVIATION...
600 PM CST

0000 UTC TAFS...WEATHER WILL START OUT QUIET FOR AVIATION
CONCERNS...BUT CONDITIONS WILL RAPIDLY DETERIORATE WITH THE
APPROACH OF THE NEXT CLIPPER.

AT ISSUANCE TIME...THE SFC LOW IS QUICKLY DROPPING SEWD THROUGH SOUTH
DAKOTA WHILE THE SFC RIDGE AXIS MOVES ACROSS ILLINOIS. SKIES WILL
START OUT SKC WITH RELATIVELY LIGHT WINDS...BUT MID AND HIGH CLOUD
WILL OVERSPREAD THE TERMINALS WITHIN A FEW HOURS. WINDS WILL
REMAIN LGT/VRBL WITH THE PASSAGE OF THE SFC RIDGE AND THEN
INCREASE AND BECOME SELY AS THE SFC LOW TRACKS ALONG THE MISSOURI
RIVER TONIGHT AND INTO NRN MISSOURI BY ARND 12Z. EXPECTS CIGS/VIS
TO QUICKLY DROP THROUGH MVFR TO IFR WITH SNOW MOVING OVER RFD BY
06Z AND THEN SPREADING EWD TO THE CHICAGO AREA TERMINALS BY 09Z.
HAVE MAINTAINED THE TEMPO GROUP FOR LIFR VIS FOR THE 12-15Z TIME
RANGE...BUT THIS MIGHT BE A LITTLE TOO CONSERVATIVE AS WINDS WILL
BE TURNING NELY FOR A PERIOD UNTIL AT LEAST 18Z AND LAKE
ENHANCEMENT TO THE SNOWFALL MAY EXTEND THE PERIOD OF LIFR VIS.

FOLLOWING THE PASSAGE OF THE SFC LOW TO THE SOUTH AND EAST...WINDS
WILL QUICKLY INCREASE...LEADING TO BLOWING AND DRIFTING OF THE
NEWLY FALLEN SNOW. SINCE TEMPERATURES WILL BE VERY LOW FOR THE
DURATION OF THE SNOWFALL...SNOW TO LIQUID RATIOS WILL BE
HIGH...CREATING A VERY DRY SNOW. HAVE TRENDED VISBY TO IFR FOR THE
24-30 HOUR PERIOD AT ORD WITH BLOWING SNOW. DRIFTING SNOW WILL
LIKELY CAUSE DIFFICULTIES FOR SNOW REMOVAL CREWS.

KREIN

&&

.MARINE...
210 PM CST

WINDS HAVE DIMINISHED ACROSS THE LAKE THIS AFTERNOON AND THEREFORE
HAVE DROPPED THE GALE AND FREEZING SPRAY WARNINGS. WINDS WILL
CONTINUE TO DIMINISH OVERNIGHT AS A RIDGE OF HIGH PRESSURE MOVES
IN ACROSS THE REGION. A LOW PRESSURE SYSTEM WILL DROP DOWN INTO
CENTRAL ILLINOIS WEDNESDAY MORNING AND THEN TRACK EASTWARD THROUGH
THE OHIO RIVER VALLEY INTO THURSDAY MORNING. WINDS WILL BE ON THE
INCREASE THURSDAY MORNING AS THE LOW REACHES THE MID ATLANTIC
COAST AND A STRONG RIDGE OF HIGH PRESSURE MOVES IN ACROSS THE
GREAT LAKES. WILL KEEP THE GALE WATCH GOING FOR THE MOMENT AS
WINDS STILL MAY GUST UP TO GALE FORCE ON THURSDAY.  THIS RIDGE
WILL SLOWLY MOVE OFF TOWARD THE SOUTHEAST US BY SATURDAY AS THE
NEXT SYSTEM TAKES AIM ON THE LAKES.

VISIBLE SATELLITE FROM TODAY REVEALS THAT THERE IS FAIRLY
EXTENSIVE ICE COVER ACROSS THE NEARSHORE ZONES EXCEPT FOR THE
FURTHEST ZONE TO THE EAST FROM BURNS HARBOR TO MICHIGAN CITY.
THEREFORE...WILL BE DROPPING THE MENTION OF WAVES IN THE NEARSHORE
FORECAST.

HALBACH

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ010-ILZ019-ILZ021-ILZ032-ILZ033-
     ILZ039...MIDNIGHT WEDNESDAY TO 6 PM WEDNESDAY.

     WIND CHILL WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...9 PM WEDNESDAY TO NOON FRIDAY.

IN...WIND CHILL WATCH...INZ001-INZ002-INZ010-INZ011-INZ019...9 PM
     WEDNESDAY TO NOON FRIDAY.

     WINTER WEATHER ADVISORY...INZ019...MIDNIGHT WEDNESDAY TO 6 PM
     WEDNESDAY.

LM...GALE WATCH...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 PM WEDNESDAY TO 1 PM THURSDAY.

&&

$$


000
FXUS63 KILX 132354
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
554 PM CST TUE JAN 13 2009

.DISCUSSION...
ISSUED 334 PM CST TUE JAN 13 2009

LATEST SURFACE ANALYSIS HAD A SKINNY RIDGE OF HIGH PRESSURE
EXTENDING FROM THE SOUTHERN PLAINS INTO THE UPPER MIDWEST. FURTHER
UPSTREAM...THE LATEST IN OUR RECENT SERIES OF CLIPPER SYSTEMS WAS
OVER THE NORTHERN HIGH PLAINS. THE SNOW CHANCES/AMOUNTS WITH THE
APPROACHING CLIPPER LATE TONIGHT INTO WEDNESDAY...AS WELL AS HOW
COLD IT WILL BE IN THE WAKE OF THE SYSTEM OVER THE NEXT COUPLE OF
DAYS ARE THE PRIMARY FORECAST CONCERNS THIS AFTERNOON.

12Z MODELS IN GOOD OVERALL AGREEMENT WITH THE CLIPPER SYSTEM...
THOUGH THERE ARE SUBTLE DIFFERENCES IN THE TRACK OF THE STORM. STILL
PREFER THE SOUTHERN MOST TRACK OF THE GFS...GIVEN THE DIGGING NATURE
OF THE MEAN UPPER TROF...WHICH WOULD SUPPORT THE HEAVIEST SNOWFALL
ALONG AND NORTH OF THE I-74 CORRIDOR. GUIDANCE TEMPERATURES STILL
SHOWING SOME SPREAD...LIKELY A RESULT OF THE STORM TRACK DIFFERENCES
AND RESULTING DIFFERENCES IN SNOWFALL. WILL TEND TO FOLLOW A BLEND
OF MODEL TEMPERATURES GIVEN LINGERING UNCERTAINTY.

SHORT TERM...TONIGHT THROUGH FRIDAY...

TONIGHT AND WEDNESDAY...CLIPPER WILL RAPIDLY DIVE SOUTHEAST
TONIGHT...LIKELY REACHING WEST CENTRAL ILLINOIS BY 12Z WEDNESDAY.
THE SYSTEM WILL CONTINUE EAST TO SOUTHERN OHIO BY 00Z THURSDAY.
STRONG WAA/ISENTROPIC LIFT AND THE CORRESPONDING LOW CONDENSATION
PRESSURE DEFICITS SUPPORT SNOW BREAKING OUT FROM NORTHWEST TO
SOUTHEAST ACROSS THE FORECAST AREA OVERNIGHT...LINGERING INTO EARLY
WEDNESDAY AS THE UPPER WAVE/JET MOVE THROUGH. THE FORCING
OVERNIGHT IS QUITE STRONG...BUT THE PERIOD OF STRONG FORCING IS
BRIEF AND THE AVAILABLE MOISTURE LIMITED. STILL...THE HIGH SNOW TO
WATER RATIO EXPECTED DUE TO THE COLD AIRMASS SUPPORTS A BAND OF
2-4 INCH SNOWS...PRIMARILY ALONG AND NORTH OF THE I-74 CORRIDOR.
LOWER SNOW TOTALS ARE EXPECTED AS YOU HEAD SOUTH FROM I-74. THERE
IS NOT A STRONG SIGNAL OF A GOOD DEFORMATION SNOW BAND ON THE BACK
SIDE OF THE CLIPPER...SO EXPECT SNOWS TO TAPER OFF PRETTY QUICKLY
WEDNESDAY. HOWEVER...AS WINDS PICK UP ON THE BACK SIDE OF THE
CLIPPER SYSTEM...WITH WIND GUSTS OVER 30 MPH...BLOWING AND
DRIFTING SNOW WILL DEVELOP ACROSS AREAS THAT RECEIVED ACCUMULATING
SNOW. THE COMBINATION OF ACCUMULATING AND BLOWING SNOW ACROSS
NORTHERN SECTIONS OF THE FORECAST AREA WILL MAKE TRAVEL TRICKY.
SO...HAVE ISSUED A WINTER WEATHER ADVISORY IN NORTHERN SECTIONS OF
THE FORECAST AREA OVERNIGHT AND WEDNESDAY.

WEDNESDAY NIGHT THROUGH FRIDAY...COLD AIR WILL CONTINUE TO SURGE
INTO THE REGION INTO AT LEAST THURSDAY NIGHT ON NORTHWEST WINDS AS
AN ARCTIC HIGH BUILDS THROUGH ILLINOIS. THIS COLD AIR WILL BE
ENHANCED ACROSS THE NORTHERN SECTIONS OF THE FORECAST AREA WHERE
SNOW COVER WILL EXIST. THIS COLD AIR WILL RESULT IN TWO NIGHTS OF
NEAR OR SUB ZERO LOWS WEDNESDAY NIGHT AND THURSDAY NIGHT AND A DAY
OF SINGLE DIGIT HIGHS ON THURSDAY. THESE BITTERLY COLD TEMPERATURES
WILL COMBINE WITH THE WIND TO PRODUCE WIND CHILL VALUES OF -15F OR
COLDER FOR MUCH OF THE PERIOD. HAVE DECIDED TO ISSUE A WIND CHILL
ADVISORY FROM 06Z THURSDAY-18Z FRIDAY FOR AREAS NORTH OF I-70 TO
ACCOUNT FOR THE BITTERLY COLD CONDITIONS. WHILE AREAS SOUTH OF I-70
SHOULD REMAIN ABOVE ADVISORY CRITERIA DUE TO SLIGHTLY WARMER
TEMPERATURES AND LITTLE/NO SNOW COVER...IT WILL STILL BE QUITE COLD
THERE TOO.

TEMPERATURES WILL BEGIN TO MODERATE SOME ON FRIDAY AS THE ARCTIC
HIGH SHIFTS EAST AND WINDS BEGIN TO TURN TO THE SOUTHWEST.

LONG TERM...SATURDAY THROUGH TUESDAY...MODELS/ENSEMBLES REMAIN IN
REASONABLE AGREEMENT WITH THE MEAN FLOW PATTERN THROUGH MUCH OF THE
EXTENDED FORECAST PERIOD...WITH A RIDGE WEST/TROF EAST CONFIGURATION
ACROSS NORTH AMERICA. HOWEVER...THE AGREEMENT WITH RESPECT TO THE
SMALLER SCALE WAVES DIVING INTO THE MEAN TROF IS STILL NOT VERY GOOD
AND GETS INCREASINGLY POOR WITH TIME. THE CORE OF THE COLDEST AIR
WITHIN THE MEAN EASTERN NORTH AMERICAN TROF IS STILL EXPECTED TO
RETREAT TO NEW ENGLAND AND EASTERN CANADA THROUGH THE PERIOD AND
THIS WILL RESULT IN A MODERATION OF TEMPERATURES. AS IN RECENT
DAYS...WILL NOT HAVE ANY MENTION OF PRECIPITATION AT THIS TIME.
WHILE SEVERAL SHORT WAVE IMPULSES ARE EXPECTED TO DIVE INTO THE MEAN
UPPER TROF DURING THE PERIOD...THESE IMPULSES WILL BE MOISTURE
STARVED AND NO STRONG MODEL CONSENSUS EXISTS ON THEIR TIMING OR
TRACK. HOWEVER...THE TRACK PREDICTED BY A BULK OF THE SOLUTIONS
SUGGESTS MOST OF THE PRECIPITATION SHOULD STAY TO OUR NORTH AND
EAST. THE MODELS ARE SIGNALING A TRANSITION TO A MORE ZONAL FLOW
PATTERN JUST BEYOND THIS FORECAST PERIOD...BUT ARE CURRENTLY ALL
OVER THE PLACE IN HOW WE WILL GET THERE. STAY TUNED.

BAK

&&

.AVIATION...
ISSUED 554 PM CST TUE JAN 13 2009...FOR THE 00Z TAFS

THE CLIPPER IS ON TRACK TO PUT DOWN 2 TO 4 INCHES OF SNOW ACROSS
THE AREA. PIA AND BMI WILL GET HIT FIRST...WITH CIGS AND VIS DOWN
TO IFR AROUND MIDNIGHT. SPI/DEC/CMI WILL BE ABOUT 2-4 HOURS BEHIND
THEM FOR SIMILAR CONDITIONS.

THE LATEST MODEL GUIDANCE IS SHOWING A SLIGHTLY FARTHER SOUTH
TRACK FOR THE LOW CENTER...WHICH WILL PUT MEASURABLE SNOW A BIT
FARTHER SOUTH AS WELL. WILL KEEP SOME LIFR VIS AT ALL TAF
SITES...WITH VLIFR POSSIBLE IN PIA AND BMI FOR THE 11Z TO 14Z TIME
FRAME.

WINDS WILL REMAIN SOUTHEAST AT 10 TO 15 KTS UNTIL MID
MORNING...THEN WILL CHANGE OVER TO NORTHWEST AND INCREASE TO 15-20
SUSTAINED AND GUSTS TO 30KTS BY AFTERNOON. CIGS WILL RISE AS
SUBSIDENCE AND DRY AIR BEHIND THE FRONT SHUT DOWN THE SNOW BY MID
DAY...BUT BLOWING SNOW WILL LIKELY PUT VIS READINGS CLOSE TO
IFR...IF NOT LIFR OR EVEN VLIFR VIS AT TIMES IN PIA AND BMI. WHITE
OUT CONDITIONS CAN NOT BE RULED OUT IF THE WINDS GET UP TO 30 KTS
AND BLOW THE FLUFFY SNOW.

WINDS WILL CONTINUE UNTIL AT LEAST 00Z TOMORROW EVENING...SO BLSN
MAY BE AN ISSUE INTO WED EVENING WHERE THE HIGHER SNOWFALL DEVELOPS.

SHIMON
&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM CST
WEDNESDAY FOR ILZ027>031-036>038-040>046.

WIND CHILL ADVISORY FROM MIDNIGHT WEDNESDAY NIGHT TO 12 PM CST
FRIDAY FOR ILZ027>031-036>038-040>057-061.

&&

$$


000
FXUS63 KLOT 132139
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
339 PM CST TUE JAN 13 2009

.DISCUSSION...
338 PM CST


ANOTHER CLIPPER SYSTEM DIVING DOWN FROM THE DAKOTAS TONIGHT IS THE
MAIN FOCUS AS MENTIONED IN PREVIOUS DISCUSSIONS. THIS ONE HOWEVER IS
TAKING A MORE SOUTHERLY TRACK AND FOCUSING HIER QPF AND SNOWFALL
TOTALS SOUTH OF I-80. GENERALLY LOOKING FOR 2-4 INCHES FROM STERLING
DOWN THRU PAXTON OVERNIGHT WITH 1-3 INCHES NORTH AND EAST OF
THERE...THEN DROPPING ANOTHER INCH OR TWO ACROSS NRN IL AND INDIANA
ON WEDNESDAY. A STRONG PRESSURE GRADIENT BEHIND THIS PASSING SYSTEM
ON WEDNESDAY WILL GUST WINDS TO 30 TO 35 MPH AND DRAW COLD ARCTIC
AIR INTO THE REGION. SOME BLOWING AND DRIFTING IS LIKELY WITH THIS
STRONG FLOW GENERALLY AFTER THE SNOW ENDS OR TAPERS TO LITE SNOW
SHOWERS. THE ONLY EXCEPTION WILL BE LAKE EFFECT SNOWS INTO NORTHEAST
IL AND NW INDY WEDNESDAY EVENING. WITH H8 TEMPS DOWN INTO THE LOWER
AND MID 20S...CAPES TO 500 JOULES IS EASILY ACCOMPLISHED. THE ISSUE
FOR WED NGT IS THE TRAJECTORY...PROTRAYED DIFFERENTLY ON WHICH MODEL
YOU CHOOSE. EVEN WITH THE WORST... WINDS TEND TO BACK TO THE NW LATE
WED EVENING TO DIRECT ANYMORE LAKE EFFECT INTO SW MICHIGAN.

HAVE DECIDED TO GO WITH AN ADVISORY IN SW SECTIONS. ACCUMULATIONS UP
TO 6 INCHES MAY BE PSBL THERE BETWEEN TNGT AND WED. BUT MAIN
EMPHASIS IS ON STRONG WINDS AND SUBZERO TEMPS THAT HAVE BEEN
ADVERTISED. WIND CHILLS OF -20 COME QUICK AFTER NIGHTFALL WED
EVENING AND PLUMMET TO -30 BEFORE SUNRISE THURSDAY. WIND CHILLS
RECOVER DURING THE DAY THURSDAY ABOVE -30 BUT DROP AGAIN THURSDAY
NIGHT INTO FRIDAY MORNING TO 30 BELOW OR LOWER. THUS HAVE A WIND
CHILL WATCH OUT STARTING WED NGT. MODELS HAVE BEEN IMPULSIVE OF LATE
WITH GENERATING STRONG WINDS...SO FURTHER RUNS MAY REDUCE THE
WARNING THREAT TO ADVISORY THREAT OF -20 TO -30.

WITH THE COLD AIR SETTLING IN FOR A WHILE...THE NEXT WARMUP FRIDAY
WILL HERALD THE NEXT CLIPPER DIVING DOWN FROM CANADA AND ANOTHER
BOUT OF SNOW.

RLB

&&

.AVIATION...
1132 AM CST

1800 UTC TAFS...GOOD WEATHER CONDITIONS ON TAP FOR THE TAF SITES
THIS AFTERNOON INTO THE EARLY EVENING TONIGHT AS SKIES CONTINUALLY
CLEAR OUT AND WINDS RAPIDLY SUBSIDE AS A RIDGE OF HIGH PRESSURE
MOVES INTO THE MIDWEST. SKIES WILL REMAIN MOSTLY CLEAR WITH JUST
SOME PASSING CONTRAILS OR THIN UPPER CLOUDS THROUGH THE EARLY
EVENING WITH WINDS GOING LIGHT AND VARIABLE.

CONDITIONS WILL QUICKLY WORSEN LATER TONIGHT FROM WEST TO EAST AS
THE NEXT CLIPPER SYSTEM DROPS INTO THE REGION. CURRENTLY IN FAR
SOUTHERN SASKATCHEWAN...A LOW PRESSURE SYSTEM WILL DROP THROUGH
THE WESTERN DAKOTAS ON INTO WEST CENTRAL ILLINOIS BY EARLY
WEDNESDAY MORNING. THIS LOW WILL THEN TRACK EASTWARD TOWARD THE
OHIO RIVER VALLEY BY THE AFTERNOON WEDNESDAY. THIS WILL BRING A
SWATH OF SNOW THAT WILL LIKELY LAST AROUND 12 HRS FROM ONSET TO
ENDING WITH VIS LIKELY DROPPING TO LIFR AT TIMES. SNOW SHOULD BE
BEGIN AT RFD AROUND 6Z AND AT DPA/ORD/MDW AROUND 9Z. CIGS WILL
RAPIDLY DROP FROM VFR TO MVFR AS THE SNOW BEGINS AND THEN ONTO IFR
AS THE HEAVIEST SNOW FALLS ON WEDNESDAY MORNING. WINDS WILL REMAIN
LIGHT AND BACK UP UNTIL LATE WEDNESDAY AFTERNOON AS THE SFC LOW
PASSES BY.

EXPECT VFR CONDITIONS THROUGH TONIGHT WHEN VIS/CIGS ARE EXPECTED
TO DROP TO IFR. SOME LIFR VIS IS LIKELY FOR A PERIOD WEDNESDAY
MORNING WHEN THE HEAVIEST SNOW IS EXPECTED.

HALBACH

&&

.MARINE...
210 PM CST

WINDS HAVE DIMINISHED ACROSS THE LAKE THIS AFTERNOON AND THEREFORE
HAVE DROPPED THE GALE AND FREEZING SPRAY WARNINGS. WINDS WILL
CONTINUE TO DIMINISH OVERNIGHT AS A RIDGE OF HIGH PRESSURE MOVES
IN ACROSS THE REGION. A LOW PRESSURE SYSTEM WILL DROP DOWN INTO
CENTRAL ILLINOIS WEDNESDAY MORNING AND THEN TRACK EASTWARD THROUGH
THE OHIO RIVER VALLEY INTO THURSDAY MORNING. WINDS WILL BE ON THE
INCREASE THURSDAY MORNING AS THE LOW REACHES THE MID ATLANTIC
COAST AND A STRONG RIDGE OF HIGH PRESSURE MOVES IN ACROSS THE
GREAT LAKES. WILL KEEP THE GALE WATCH GOING FOR THE MOMENT AS
WINDS STILL MAY GUST UP TO GALE FORCE ON THURSDAY.  THIS RIDGE
WILL SLOWLY MOVE OFF TOWARD THE SOUTHEAST US BY SATURDAY AS THE
NEXT SYSTEM TAKES AIM ON THE LAKES.

VISIBLE SATELLITE FROM TODAY REVEALS THAT THERE IS FAIRLY
EXTENSIVE ICE COVER ACROSS THE NEARSHORE ZONES EXCEPT FOR THE
FURTHEST ZONE TO THE EAST FROM BURNS HARBOR TO MICHIGAN CITY.
THEREFORE...WILL BE DROPPING THE MENTION OF WAVES IN THE NEARSHORE
FORECAST.

HALBACH

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ010-ILZ019-ILZ021-ILZ032-ILZ033-
     ILZ039...MIDNIGHT WEDNESDAY TO 6 PM WEDNESDAY.

     WIND CHILL WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039...9 PM WEDNESDAY TO NOON FRIDAY.

IN...WIND CHILL WATCH...INZ001-INZ002-INZ010-INZ011-INZ019...9 PM
     WEDNESDAY TO NOON FRIDAY.

     WINTER WEATHER ADVISORY...INZ019...MIDNIGHT WEDNESDAY TO 6 PM
     WEDNESDAY.

LM...GALE WATCH...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 PM WEDNESDAY TO 1 PM THURSDAY.

&&

$$


000
FXUS63 KILX 132034
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
234 PM CST TUE JAN 13 2009

.DISCUSSION...
ISSUED 334 PM CST TUE JAN 13 2009

LATEST SURFACE ANALYSIS HAD A SKINNY RIDGE OF HIGH PRESSURE
EXTENDING FROM THE SOUTHERN PLAINS INTO THE UPPER MIDWEST. FURTHER
UPSTREAM...THE LATEST IN OUR RECENT SERIES OF CLIPPER SYSTEMS WAS
OVER THE NORTHERN HIGH PLAINS. THE SNOW CHANCES/AMOUNTS WITH THE
APPROACHING CLIPPER LATE TONIGHT INTO WEDNESDAY...AS WELL AS HOW
COLD IT WILL BE IN THE WAKE OF THE SYSTEM OVER THE NEXT COUPLE OF
DAYS ARE THE PRIMARY FORECAST CONCERNS THIS AFTERNOON.

12Z MODELS IN GOOD OVERALL AGREEMENT WITH THE CLIPPER SYSTEM...
THOUGH THERE ARE SUBTLE DIFFERENCES IN THE TRACK OF THE STORM. STILL
PREFER THE SOUTHERN MOST TRACK OF THE GFS...GIVEN THE DIGGING NATURE
OF THE MEAN UPPER TROF...WHICH WOULD SUPPORT THE HEAVIEST SNOWFALL
ALONG AND NORTH OF THE I-74 CORRIDOR. GUIDANCE TEMPERATURES STILL
SHOWING SOME SPREAD...LIKELY A RESULT OF THE STORM TRACK DIFFERENCES
AND RESULTING DIFFERENCES IN SNOWFALL. WILL TEND TO FOLLOW A BLEND
OF MODEL TEMPERATURES GIVEN LINGERING UNCERTAINTY.

SHORT TERM...TONIGHT THROUGH FRIDAY...

TONIGHT AND WEDNESDAY...CLIPPER WILL RAPIDLY DIVE SOUTHEAST
TONIGHT...LIKELY REACHING WEST CENTRAL ILLINOIS BY 12Z WEDNESDAY.
THE SYSTEM WILL CONTINUE EAST TO SOUTHERN OHIO BY 00Z THURSDAY.
STRONG WAA/ISENTROPIC LIFT AND THE CORRESPONDING LOW CONDENSATION
PRESSURE DEFICITS SUPPORT SNOW BREAKING OUT FROM NORTHWEST TO
SOUTHEAST ACROSS THE FORECAST AREA OVERNIGHT...LINGERING INTO EARLY
WEDNESDAY AS THE UPPER WAVE/JET MOVE THROUGH. THE FORCING
OVERNIGHT IS QUITE STRONG...BUT THE PERIOD OF STRONG FORCING IS
BRIEF AND THE AVAILABLE MOISTURE LIMITED. STILL...THE HIGH SNOW TO
WATER RATIO EXPECTED DUE TO THE COLD AIRMASS SUPPORTS A BAND OF
2-4 INCH SNOWS...PRIMARILY ALONG AND NORTH OF THE I-74 CORRIDOR.
LOWER SNOW TOTALS ARE EXPECTED AS YOU HEAD SOUTH FROM I-74. THERE
IS NOT A STRONG SIGNAL OF A GOOD DEFORMATION SNOW BAND ON THE BACK
SIDE OF THE CLIPPER...SO EXPECT SNOWS TO TAPER OFF PRETTY QUICKLY
WEDNESDAY. HOWEVER...AS WINDS PICK UP ON THE BACK SIDE OF THE
CLIPPER SYSTEM...WITH WIND GUSTS OVER 30 MPH...BLOWING AND
DRIFTING SNOW WILL DEVELOP ACROSS AREAS THAT RECEIVED ACCUMULATING
SNOW. THE COMBINATION OF ACCUMULATING AND BLOWING SNOW ACROSS
NORTHERN SECTIONS OF THE FORECAST AREA WILL MAKE TRAVEL TRICKY.
SO...HAVE ISSUED A WINTER WEATHER ADVISORY IN NORTHERN SECTIONS OF
THE FORECAST AREA OVERNIGHT AND WEDNESDAY.

WEDNESDAY NIGHT THROUGH FRIDAY...COLD AIR WILL CONTINUE TO SURGE
INTO THE REGION INTO AT LEAST THURSDAY NIGHT ON NORTHWEST WINDS AS
AN ARCTIC HIGH BUILDS THROUGH ILLINOIS. THIS COLD AIR WILL BE
ENHANCED ACROSS THE NORTHERN SECTIONS OF THE FORECAST AREA WHERE
SNOW COVER WILL EXIST. THIS COLD AIR WILL RESULT IN TWO NIGHTS OF
NEAR OR SUB ZERO LOWS WEDNESDAY NIGHT AND THURSDAY NIGHT AND A DAY
OF SINGLE DIGIT HIGHS ON THURSDAY. THESE BITTERLY COLD TEMPERATURES
WILL COMBINE WITH THE WIND TO PRODUCE WIND CHILL VALUES OF -15F OR
COLDER FOR MUCH OF THE PERIOD. HAVE DECIDED TO ISSUE A WIND CHILL
ADVISORY FROM 06Z THURSDAY-18Z FRIDAY FOR AREAS NORTH OF I-70 TO
ACCOUNT FOR THE BITTERLY COLD CONDITIONS. WHILE AREAS SOUTH OF I-70
SHOULD REMAIN ABOVE ADVISORY CRITERIA DUE TO SLIGHTLY WARMER
TEMPERATURES AND LITTLE/NO SNOW COVER...IT WILL STILL BE QUITE COLD
THERE TOO.

TEMPERATURES WILL BEGIN TO MODERATE SOME ON FRIDAY AS THE ARCTIC
HIGH SHIFTS EAST AND WINDS BEGIN TO TURN TO THE SOUTHWEST.

LONG TERM...SATURDAY THROUGH TUESDAY...MODELS/ENSEMBLES REMAIN IN
REASONABLE AGREEMENT WITH THE MEAN FLOW PATTERN THROUGH MUCH OF THE
EXTENDED FORECAST PERIOD...WITH A RIDGE WEST/TROF EAST CONFIGURATION
ACROSS NORTH AMERICA. HOWEVER...THE AGREEMENT WITH RESPECT TO THE
SMALLER SCALE WAVES DIVING INTO THE MEAN TROF IS STILL NOT VERY GOOD
AND GETS INCREASINGLY POOR WITH TIME. THE CORE OF THE COLDEST AIR
WITHIN THE MEAN EASTERN NORTH AMERICAN TROF IS STILL EXPECTED TO
RETREAT TO NEW ENGLAND AND EASTERN CANADA THROUGH THE PERIOD AND
THIS WILL RESULT IN A MODERATION OF TEMPERATURES. AS IN RECENT
DAYS...WILL NOT HAVE ANY MENTION OF PRECIPITATION AT THIS TIME.
WHILE SEVERAL SHORT WAVE IMPULSES ARE EXPECTED TO DIVE INTO THE MEAN
UPPER TROF DURING THE PERIOD...THESE IMPULSES WILL BE MOISTURE
STARVED AND NO STRONG MODEL CONSENSUS EXISTS ON THEIR TIMING OR
TRACK. HOWEVER...THE TRACK PREDICTED BY A BULK OF THE SOLUTIONS
SUGGESTS MOST OF THE PRECIPITATION SHOULD STAY TO OUR NORTH AND
EAST. THE MODELS ARE SIGNALING A TRANSITION TO A MORE ZONAL FLOW
PATTERN JUST BEYOND THIS FORECAST PERIOD...BUT ARE CURRENTLY ALL
OVER THE PLACE IN HOW WE WILL GET THERE. STAY TUNED.

BAK
&&

.AVIATION...
ISSUED 1115 AM CST TUE JAN 13 2009

CLEARING LINE HAS BEEN MOVING STEADILY EASTWARD THIS MORNING...
HOWEVER EXPECT 1K-2K FT STRATOCU TO CONTINUE OVER THE DEC/CMI AREAS
THRU 00Z WED AS NWLY SFC WNDS COME OFF THE SNOW FIELD TO THE NW. WND
SPEEDS WILL DECREASE WITH TIME AS A NARROW SFC RIDGE MOVES TO
CENTRAL IL BY 00Z WED. THIS RIDGE WILL CONTINUE ITS RAPID EWD TREK
OUT OF THE AREA...TO BE REPLACED BY A VIGOROUS SHORTWAVE NOW
ENTERING THE DAKOTAS. THE ASSOCIATED SFC LOW WILL MOVE SEWD TO SERN
IA BY 12Z WED...THEN ACROSS SPI/DEC/CMI BEFORE 18Z. SNOW WILL BEGIN
TO AFFECT THE TERMINALS BY 06Z WED AND CONTINUE THROUGH 18Z.
HEAVIEST SNOW EXPECTED JUST N OF THE SFC LOW TRACK...WHICH WILL BE
NEAR PIA/BMI. HOWEVER...WIDESPREAD IFR CONDITIONS WILL AFFECT ALL
TERMINALS. SFC WNDS WILL BE QUITE VARIABLE IN DIRECTION AS THE LOW
MOVES ACROSS 12Z-18Z WED...BUT UNTIL THEN EXPECT SELY WNDS TO
INCREASE BEGINNING 03Z-06Z WED.

04
&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM CST
WEDNESDAY FOR ILZ027>031-036>038-040>046.

WIND CHILL ADVISORY FROM MIDNIGHT WEDNESDAY NIGHT TO 12 PM CST
FRIDAY FOR ILZ027>031-036>038-040>057-061.

&&

$$


000
FXUS63 KLOT 132010
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
210 PM CST TUE JAN 13 2009

.DISCUSSION...
1102 AM CST

HAVE REMOVED THE BLIZZARD WATCH. LATEST MODEL GUIDANCE HAS REALLY
CUT BACK ON WIND SPEED WED INTO WED NGT. STILL LIKELY TO BE SOME
BLOWING SNOW WED AFTER OVERNIGHT AND MRNG SNOWFALL WITH THE NEXT
INCOMING CLIPPER. MAY BE CONSIDERING SNOW AND BLOWING SNOW
ADVISORY FOR TONIGHT THRU WED. LATEST QPF INDICATING HIGHEST SNOW
POTENTIAL SHIFT SOUTH OF I-80. HOWEVER SOME LAKE EFFECT WITH THE
COLD AIR PLUNGE SPREADING BRIEFLY WED NGT INTO CHI AREA AND NW
INDY AND MAY HAVE TO CONSIDER ADVISORY CRITERIA FOR CHI AS WELL.
WILL MORE THAN LIKELY HAVE AN ADVISORY GOING BUT WILL BE DEBATING
LENGTH AND EXTENT OF IT WITH THE AFTN FCST PACKAGE.

RLB

&&

.AVIATION...
1132 AM CST

1800 UTC TAFS...GOOD WEATHER CONDITIONS ON TAP FOR THE TAF SITES
THIS AFTERNOON INTO THE EARLY EVENING TONIGHT AS SKIES CONTINUALLY
CLEAR OUT AND WINDS RAPIDLY SUBSIDE AS A RIDGE OF HIGH PRESSURE
MOVES INTO THE MIDWEST. SKIES WILL REMAIN MOSTLY CLEAR WITH JUST
SOME PASSING CONTRAILS OR THIN UPPER CLOUDS THROUGH THE EARLY
EVENING WITH WINDS GOING LIGHT AND VARIABLE.

CONDITIONS WILL QUICKLY WORSEN LATER TONIGHT FROM WEST TO EAST AS
THE NEXT CLIPPER SYSTEM DROPS INTO THE REGION. CURRENTLY IN FAR
SOUTHERN SASKATCHEWAN...A LOW PRESSURE SYSTEM WILL DROP THROUGH
THE WESTERN DAKOTAS ON INTO WEST CENTRAL ILLINOIS BY EARLY
WEDNESDAY MORNING. THIS LOW WILL THEN TRACK EASTWARD TOWARD THE
OHIO RIVER VALLEY BY THE AFTERNOON WEDNESDAY. THIS WILL BRING A
SWATH OF SNOW THAT WILL LIKELY LAST AROUND 12 HRS FROM ONSET TO
ENDING WITH VIS LIKELY DROPPING TO LIFR AT TIMES. SNOW SHOULD BE
BEGIN AT RFD AROUND 6Z AND AT DPA/ORD/MDW AROUND 9Z. CIGS WILL
RAPIDLY DROP FROM VFR TO MVFR AS THE SNOW BEGINS AND THEN ONTO IFR
AS THE HEAVIEST SNOW FALLS ON WEDNESDAY MORNING. WINDS WILL REMAIN
LIGHT AND BACK UP UNTIL LATE WEDNESDAY AFTERNOON AS THE SFC LOW
PASSES BY.

EXPECT VFR CONDITIONS THROUGH TONIGHT WHEN VIS/CIGS ARE EXPECTED
TO DROP TO IFR. SOME LIFR VIS IS LIKELY FOR A PERIOD WEDNESDAY
MORNING WHEN THE HEAVIEST SNOW IS EXPECTED.

HALBACH

&&

.MARINE...
210 PM CST

WINDS HAVE DIMINISHED ACROSS THE LAKE THIS AFTERNOON AND THEREFORE
HAVE DROPPED THE GALE AND FREEZING SPRAY WARNINGS. WINDS WILL
CONTINUE TO DIMINISH OVERNIGHT AS A RIDGE OF HIGH PRESSURE MOVES
IN ACROSS THE REGION. A LOW PRESSURE SYSTEM WILL DROP DOWN INTO
CENTRAL ILLINOIS WEDNESDAY MORNING AND THEN TRACK EASTWARD THROUGH
THE OHIO RIVER VALLEY INTO THURSDAY MORNING. WINDS WILL BE ON THE
INCREASE THURSDAY MORNING AS THE LOW REACHES THE MID ATLANTIC
COAST AND A STRONG RIDGE OF HIGH PRESSURE MOVES IN ACROSS THE
GREAT LAKES. WILL KEEP THE GALE WATCH GOING FOR THE MOMENT AS
WINDS STILL MAY GUST UP TO GALE FORCE ON THURSDAY.  THIS RIDGE
WILL SLOWLY MOVE OFF TOWARD THE SOUTHEAST US BY SATURDAY AS THE
NEXT SYSTEM TAKES AIM ON THE LAKES.

VISIBLE SATELLITE FROM TODAY REVEALS THAT THERE IS FAIRLY
EXTENSIVE ICE COVER ACROSS THE NEARSHORE ZONES EXCEPT FOR THE
FURTHEST ZONE TO THE EAST FROM BURNS HARBOR TO MICHIGAN CITY.
THEREFORE...WILL BE DROPPING THE MENTION OF WAVES IN THE NEARSHORE
FORECAST.

HALBACH

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WATCH...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 PM WEDNESDAY TO 1 PM THURSDAY.

&&

$$