Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 271742
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1242 PM CDT MON OCT 27 2008

.DISCUSSION...
ISSUED 1130 AM CDT MON OCT 27 2008

FORECAST IN GOOD SHAPE TODAY AND ONLY MINOR TWEAKS TO INCREASE THE
NW WINDS AND HIGHS SLIGHTLY IN A FEW SPOTS. MOSTLY CLOUDY...VERY
BREEZY AND COOL TODAY WITH A CHANCE OF SPRINKLES AND FLURRIES.
HIGHS ONLY IN THE MIDDLE TO UPPER 40S. MUCH COOLER THAN NORMAL
HIGHS FOR LATE OCT IN THE UPPER 50S AND LOWER 60S.

16Z/11 AM SURFACE MAP SHOWS STRONG 998 MB LOW PRESSURE OVER
NORTHERN QUEBEC WITH ITS COLD FRONT OFF THE ALTANTIC AND GULF
COAST. A SURFACE TROF EXTENDED SW FROM THE LOW INTO NW OH AND SE
INDIANA. STRONG 1042 MB ELONGATED HIGH PRESSURE WAS ACROSS THE
HIGH PLAINS FROM NORTH TX NORTHWARD ACROSS THE WESTERN DAKOTAS.
TIGHT PRESSURE GRADIENT REMAINS OVER IL WITH BREEZY NW WINDS 12 TO
20 MPH AND GUSTS IN THE 20S. TEMPS WERE IN THE LOW TO MID 40S.
BROKEN TO OVERCAST LOW CLOUDS WERE DROPPING QUICKLY SSE ACROSS
CENTRAL IL TOWARD I-70. THIS ASSOCIATED WITH VERY STRONG UPPER
LEVEL TROF EXTENDING FROM HUDSON BAY CANADA SOUTHWARD ACROSS THE
GREAT LAKES AND INTO KY/TN. A FEW EMBEDDED SHORT WAVES DROPPING
SSE ACROSS THE MIDWEST...ONE OVER SOUTHERN IL AND ANOTHER OVER
NORTHERN WI.

STEEP LAPSE RATES WITH UPPER LEVEL TROF NEAR IL TO KEEP MOSTLY
CLOUDY TO OVERCAST SKIES OVER CENTRAL IL TODAY AND DEVELOP OVER SE
IL BY 18Z/1 PM. SHORT WAVE IN NORTHERN WI TO DROP SSE ACROSS
NE AND EAST CENTRAL IL THIS AFTERNOON AND BRING A CHANCE OF VERY
LIGHT SHOWERS OR SPRINKLES (POSSIBLY FLURRIES FROM PEORIA AND
BLOOMINGTON NORTH). BEST CHANCE OF SHOWERS THIS AFTERNOON WILL BE
OVER NE IL. BUFKIT MOMENTUM TRANSFERS SHOW NW WIND GUSTS OF 25 TO
35 MPH TODAY WITH HIGHEST WIND GUSTS AT BMI AND CMI. WIDESPREAD
LOW CLOUDS COMBINED WITH STRONG NW WINDS TO ONLY ALLOW TEMPS TO
CLIMB A DEGREE OR TWO WITH HIGHS TODAY IN THE MID TO UPPER 40S.

A FREEZE WARNING CONTINUES OVERNIGHT AND EARLY TUE MORNING WITH A
WIDESPREAD HARD FREEZE OVER CENTRAL IL WITH LOWS 25 TO 30F.

HUETTL

&&

.AVIATION...
ISSUED 1240 PM CDT MON OCT 27 2008

VFR CONDITIONS SHOULD PREVAIL ACROSS THE CENTRAL ILLINOIS TEMINALS
THROUGH 18Z/TUE. VERY STRONG UPPER LEVEL TROF FROM HUDSON BAY
SOUTHWARD ACROSS THE GREAT LAKES INTO THE OH/TN VALLEYS WILL SHIFT
EASTWARD INTO THE ATLANTIC STATES TUE. A SHORT WAVE OVER CENTRAL
WI WILL DIVE SSE ACROSS NE/EAST CENTRAL IL THIS AFTERNOON BRINGING
A FEW LIGHT SHOWERS TO MAINLY NE IL. DID NOT ADD SHOWERS TO
CENTRAL IL TAF SITES THINKING JUST SPRINKLES WITH VSBYS STAYING
ABOVE 5 MILES AND BEST CHANCE ALONG I-74. BROKEN TO OVERCAST
STRATOCUMULUS CLOUDS OF 4 TO 6K FT AND AS LOW AS 3 TO 4K FT AT CMI
AND BMI THIS AFTERNOON TO CLEAR FROM NW TO SE DURING THIS EVENING
WITH CLEAR SKIES OVERNIGHT. BREEZY NW WINDS 12 TO 17 KTS AND GUSTS
OF 22 TO 28 KTS TO DIMINISH TO AROUND 10 KTS DURING THIS EVENING.
STRONG ELONGATED HIGH PRESSURE FROM NORTH TX INTO THE WESTERN
DAKOTAS TO BUILD EASTWARD TO ALONG THE TX/LA BORDER NORTHWARD ACROSS
MO/IA/MN BY TUE AFTERNOON. THIS TO BRING MOSTLY SUNNY SKIES TO
CENTRAL IL TUE WITH SCATTERED CU/STRATO CU CLOUDS AFTER 15Z/TUE
WITH NW WINDS 10 TO 15 KTS.

HUETTL

&&

.PREV DISCUSSION...
ISSUED 139 AM CDT MON OCT 27 2008

UNSEASONABLY COLD WEATHER TO TAKE HOLD ACROSS CENTRAL ILLINOIS FOR
THE NEXT COUPLE OF DAYS...BEFORE WARMER CONDITIONS RETURN FOR THE
END OF THE WEEK.

06Z SURFACE CHART SHOWS POLAR FRONT DIVING SOUTHWARD TOWARD THE GULF
COAST...WHILE 1042MB HIGH BUILDS SOUTHWARD INTO THE NORTHERN
ROCKIES. SHARPLY COLDER AIRMASS CONTINUES TO SPILL INTO CENTRAL
ILLINOIS ON GUSTY NORTHWESTERLY WINDS...AS EVIDENCED BY CURRENT
TEMPS DIPPING INTO THE UPPER 30S. ALOFT...UPPER LOW CENTERED OVER
ONTARIO...WITH DEEP TROUGH DIGGING SOUTHWARD INTO THE GREAT
LAKES/MIDWEST.

SHORT TERM...TODAY THROUGH WEDNESDAY
STRONGLY CYCLONIC FLOW WILL PREVAIL ACROSS THE MIDWEST
TODAY...ENSURING MOSTLY CLOUDY SKIES. LATEST SATELLITE LOOPS
INDICATE PLENTY OF LOW-LEVEL CLOUDINESS ACROSS CENTRAL ILLINOIS AND
EXTENDING WELL UPSTREAM INTO THE EASTERN DAKOTAS. EVEN IF A FEW
BREAKS DEVELOP IN THE OVERCAST...COLD TEMPS ALOFT AND RESULTING
STEEP LAPSE RATES WILL ALLOW CLOUDS TO QUICKLY FILL BACK IN. MAY
EVEN SEE A FEW SPRINKLES OR FLURRIES AT TIMES...AS WEAK IMPULSES
CONTINUE TO DROP SOUTHWARD INTO THE MEAN TROUGH POSITION. WILL ALSO
BE ANOTHER WINDY DAY...WITH FORECAST SOUNDINGS SUGGESTING WINDS
GUSTING TO BETWEEN 25 AND 30MPH. GIVEN THE STRONG CAA AND CLOUD
COVER...TEMPS WILL STRUGGLE TO RECOVER. HAVE THEREFORE FOLLOWED THE
COOLER MET GUIDANCE NUMBERS MOST CLOSELY...WITH HIGHS MAINLY IN THE
MIDDLE 40S.

SURFACE HIGH WILL BEGIN TO SHIFT EASTWARD TONIGHT...GRADUALLY
PUSHING THE MID AND LOW-LEVEL MOISTURE FURTHER EAST INTO INDIANA.
MODELS IN FAIRLY GOOD AGREEMENT WITH THIS PROCESS...WITH THE GFS
BEING A BIT FASTER THAN THE NAM-WRF. GIVEN STRENGTH OF UPPER TROUGH
AND DEGREE OF CYCLONIC FLOW...PREFER THE SLOWER NAM-WRF. WILL
THEREFORE START THE EVENING OUT MOSTLY CLOUDY ACROSS THE BOARD...
WITH SKIES CLEARING FROM WEST TO EAST AFTER MIDNIGHT. WITH CLEAR
SKIES AND DIMINISHING WINDS...LOW TEMPS TONIGHT WILL DROP WELL BELOW
FREEZING ACROSS ALL OF CENTRAL AND SOUTHEAST ILLINOIS. WILL
THEREFORE ISSUE A FREEZE WARNING FOR THE ENTIRE KILX CWA...AS TEMPS
DIP INTO THE MIDDLE TO UPPER 20S. ANOTHER VERY COOL DAY WILL BE IN
STORE FOR TUESDAY...AS SURFACE HIGH REMAINS WEST OF THE MISSISSIPPI
RIVER AND LOW-LEVEL FLOW STAYS NORTHWESTERLY. HIGH TEMPS WILL AGAIN
STRUGGLE TO RISE THROUGH THE 40S...WHILE EARLY MORNING LOWS
WEDNESDAY WILL AGAIN DROP INTO THE 20S.

LONG TERM...THURSDAY THROUGH SUNDAY
HIGH PRESSURE WILL SHIFT EAST OF THE REGION WEDNESDAY NIGHT AND
THURSDAY...ALLOWING SOUTHERLY RETURN FLOW TO DEVELOP AND WARMER
TEMPS TO MAKE A COMEBACK ACROSS CENTRAL ILLINOIS. 850MB TEMPS
REBOUND TO AROUND 10C ON THURSDAY...SUGGESTING HIGH TEMPS RISING
INTO THE LOWER TO MIDDLE 60S. AFTER THAT...THE MEDIUM RANGE MODELS
CONTINUE TO INDICATE A NORTHERN STREAM WAVE TRACKING ACROSS SOUTHERN
CANADA/NORTHERN GREAT LAKES BY LATE IN THE WEEK. 12Z ECMWF/00Z GFS
ARE IN EXCELLENT AGREEMENT CONCERNING THE TRACK AND TIMING OF THIS
SYSTEM...AS WELL AS ITS ASSOCIATED COLD FRONT. BOTH MODELS BRING A
WEAK COLD FRONT THROUGH ILLINOIS ON FRIDAY...HOWEVER AIRMASS IS TOO
DRY TO SUPPORT ANY PRECIP ALONG THE BOUNDARY. AFTER THAT...DRY AND
COOL WEATHER CAN BE EXPECTED OVER THE WEEKEND...AS CANADIAN HIGH
PRESSURE BUILDS SOUTHWARD INTO THE REGION.

BARNES


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
FREEZE WARNING FROM 1 AM TO 9 AM CDT TUESDAY FOR ILZ027>031-
036>038-040>057-061>063-066>068-071>073.

&&

$$








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  • Page last modified: Aug 26th, 2008 18:04 UTC
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