000
FXUS62 KTAE 170636
AFDTAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
236 AM EDT FRI OCT 17 2008

.SYNOPSIS...03 UTC SURFACE ANALYSIS SHOWS A COLD FRONT ACROSS THE
SOUTHEAST FROM NORTHWEST LOUISIANA INTO EASTERN TENNESSEE AND ACROSS
SOUTHERN VIRGINIA. AN AREA OF HIGH PRESSURE WAS ANALYZED ACROSS
MINNESOTA. CONSIDERABLY COOLER AND DRIER AIR WAS NOTED BEHIND THIS
COLD FRONT. SATELLITE OR RADAR IMAGERY THIS EVENING DOES NOT
INDICATE MUCH IN THE WAY OF SHOWER ACTIVITY ALONG THIS BOUNDARY IN
THE SOUTHEAST. THE UPPER AIR PATTERN IS NOT VERY AMPLIFIED AT THIS
TIME WITH A TROF MOVING ACROSS THE WESTERN HIGH PLAINS. THIS TROF IS
PROGGED TO DEEPEN AS IT NEARS THE EASTERN SEABOARD AND PUSH THIS
COLD FRONT THROUGH OUR REGION BY SATURDAY MORNING. THE LARGE DEEP
LAYER RIDGE REMAINS PARKED OVER THE NORTHERN GULF OF MEXICO.

&&

.SHORT TERM...(TODAY THROUGH SUNDAY).
FORECAST FOR THE SHORT TERM PERIOD IS FOCUSED PRIMARILY ON THE
PROGRESSION OF THE COLD FRONT THROUGH THE SOUTHEAST. OVER THE LAST
SEVERAL RUNS THE GENERAL TREND HAS BEEN FOR THE FRONT TO CLEAR MUCH
OF OUR CWA BY 12Z SATURDAY. THE OVERRIDING TREND IN THE GFS HAS BEEN
FOR STRONGER FORCING...THUS MORE QPF. THE NAM IS A LITTLE WEAKER
WITH THE FORCING ON THE SOUTHERN EXTENT OF THE FRONTAL SYSTEM...AND
ALSO STRINGS OUT THE MOISTURE A LITTLE BIT. VAPOR IMAGERY EARLY THIS
MORNING SHOWS THE TROF OVER THE UPPER PLAINS BEGINNING TO DEEPEN AS
IT APPROACHES THE MISSISSIPPI RIVER VALLEY. WITH THE TROF AMPLIFYING
WHILE MOVING EASTWARD...ASSOCIATED Q-G FORCING WILL INCREASE WITH
TIME AND BE STRONGEST NEARER THE GREATEST HEIGHT FALLS OVER
NORTHEAST TENNESSEE AND WESTERN NORTH CAROLINA. THE TREND IN THE MOS
HAS BEEN FOR HIGHER POPS FOR TODAY AND TONIGHT. THIS SEEMS TO MAKE
SENSE GIVEN THE DEEP LAYER MOISTURE AND FORCING ACCOMPANYING THE
FRONT. WITH THE FRONT STILL LOCATED ACROSS THE MID SOUTH...WILL KEEP
POPS RELATIVELY LOW IN THE NORTHWESTERN ZONES AS IT WILL TAKE SOME
TIME FOR THE FRONT TO KICK IT INTO GEAR AND MOVE EASTWARD AS THE
TROF FINALLY CATCHES UP THIS AFTERNOON. WILL THEREFORE KEEP ALL POPS
LESS THAN 10 PERCENT PRIOR TO 18Z TODAY. AFTER 18Z...WILL SHOW AN
INCREASING TREND WITH POPS...BUT SHOULD REMAIN ALL DRY EAST OF A
LINE FROM FITZGERALD TO PANAMA CITY. WILL BE QUITE WARM AGAIN IN THE
EASTERN CWA WHERE CLOUD COVER WILL ARRIVE LATE IN THE DAY.
TEMPERATURES WILL ONCE AGAIN APPROACH 90 IN THE SUWANNEE RIVER
VALLEY...BUT WE SHOULD REMAIN BELOW ANY RECORDS FOR THE DATE (THE
DAILY MAX RECORD FOR TLH IS 90).

TONIGHT...WITH A RAPIDLY DEEPENING TROF...THE COLD FRONT IS EXPECTED
TO MOVE THROUGH THE REGION OVERNIGHT AND APPROACH OUR SOUTHEASTERN
CWA BORDER BY 12Z. A LINE OF SHOWERS SHOULD PRECEDE THIS FRONT. WITH
FORCING GREATEST IN THE EVENING AND EARLY MORNING HOURS IN OUR
NORTHERN ZONES...THINK IT IS APPROPRIATE AT THIS TIME TO INCREASE
POPS TO THE LIKELY CATEGORY. THE NEW NAM MOS SEEMS A LITTLE TOO HIGH
FOR MY TASTE AT THIS POINT WITH POPS NEAR 80 PERCENT AT ALBANY.
GENERALLY USED A BLEND OF THE NEW NAMMOS/MAVMOS AND SREF TO ARRIVE
AT THE POP GRID FOR THIS PERIOD. GIVEN THE FORCING
AVAILABLE...CONSIDERED KEEPING THE ISOLATED THUNDER IN THE
FORECAST...BUT LAPSE RATES APPROACH 6 DEG C/KM WITH THE
FRONT...PRODUCING NEGLIGIBLE CAPE (25 J/KG OR LESS)...SO WILL REMOVE
THE THUNDER FROM THE FORECAST OVER THE LANDMASS.

SATURDAY...THE COLD FRONT SHOULD CLEAR CROSS CITY BY 15Z WITH MUCH
DRIER AND COOLER AIR FILTERING INTO THE CWA THROUGHOUT THE DAY. MAX
TEMPERATURES WILL DROP BACK INTO THE UPPER 70S TO LOW 80S...BUT THE
COOLER DAY WILL BE ON SUNDAY.

SATURDAY NIGHT...SURFACE PRESSURE GRADIENT REMAINS TIGHT AS A
SURFACE HIGH SLIDES DOWN THE EASTERN SEABOARD. THIS WILL KEEP
SURFACE WINDS ABOVE 5 MPH THROUGHOUT MUCH OF THE NIGHT AND WILL
PREVENT TEMPERATURES FROM PLUMMETING TOO FAR. LATEST GUIDANCE HAS
BEEN WAFFLING BETWEEN LOW 50S AND UPPER 40S. THIS RUN IS LARGELY IN
THE UPPER 40S ALL INLAND SITES. GIVEN THE WIND...WOULD PREFER TO GO
TOWARD A WARMER SOLUTION OF THE LOW 50S...EXCEPT FAR NORTHWESTERN
ZONES WHERE THERE IS THE POTENTIAL SHELTERED LOCATIONS MAY GO CALM
TOWARD DAYBREAK.

SUNDAY...BREEZY NORTHEAST WINDS WILL HELP SUNDAY FEEL LIKE A TRUE
FALL DAY WITH TEMPERATURES ONLY MAKING IT INTO THE MID 70S AREA WIDE
UNDER FULL SUNSHINE.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY).
HIGH PRESSURE WILL BE IN CONTROL OF THE WEATHER AT THE START OF THE
PERIOD WITH A SURFACE RIDGE EXTENDING FROM THE NE/MID ATLANTIC SWWD
ACROSS THE DEEP S. THIS WILL PROVIDE THE AREA WITH ANOTHER COOL DAY
ON MON, WITH MINS SIMILAR TO SUN...SEVERAL DEGREES BELOW NORMAL...
AND MAX TEMPS JUST A FEW DEGREES WARMER. UPPER LEVEL RIDGING WILL
THEN MOVE EWD FROM THE SRN PLAINS WITH BOTH MAX AND MIN TEMPS
MODERATING TO SLIGHTLY ABOVE NORMAL BY TUE-WED. BY MID WEEK...WE
BEGIN TO SEE SOME SIGNIFICANT DIFFERENCES DEVELOP IN THE MODEL
SOLUTIONS. BOTH THE GFS AND 16/12Z EURO OPERATIONAL RUNS DEEPEN A
TROUGH OVER CENTRAL N AMERICA. HOWEVER...THE GFS DROPS THE OCCLUDED
SYSTEM MUCH FURTHER S AND W THAN THE EURO...INTO THE CENTRAL
PLAINS...WHERE IT SITS AND SPINS FOR DAYS. THE EURO BRINGS THE
STACKED LOW INTO THE UPPER MS VALLEY AND THEN SWINGS IT EWD ACROSS
THE LAKES INTO THE WEEKEND. THESE DIFFERENCES IMPACT DEVELOPMENTS IN
THE TROPICS AS WELL, WHERE BOTH MODELS SHOW LOW PRESSURE DEVELOPING
IN THE NWRN CARIBBEAN SEA. THE EURO`S TROUGH IS FAR ENOUGH N THAT IT
DOES NOT PICK UP THIS FEATURE WHICH SPINS IN PLACE THROUGH MOST OF
NEXT WEEK. THE GFS PICKS UP THE LOW AND LIFTS IT SLOWLY NWD THROUGH
THE YUCATAN CHANNEL INTO THE SERN GULF OF MEXICO FROM WED-FRI. WITH
THE FRONT STALLED UPSTREAM AND MOISTURE INCREASING FROM THE S AND
E...THE GFS PRESENTS A MUCH CLOUDIER AND BREEZIER SCENARIO FOR LATE
IN THE WEEK THAN THE EURO...WHICH SHOWS A CLEAN COLD FROPA ON FRI.
THE GFS ENSEMBLE MEAN IS MUCH CLOSER TO THE EURO SOLUTION WITH
RESPECT OT THE POSITION OF THE 500 MB HIGH ON FRI. CONSIDERING THE
SPREAD OF THE ENSEMBLE MEMBERS THROUGH, WE ARE NOT CONFIDENT ENOUGH
TO GO STRICTLY WITH THE EURO. WE WILL GENERALLY FOLLOW THE GFS/MEX
FOR POP...BUT WILL SCALE BACK THE AMOUNT OF CLOUD COVER AND ELY
WINDS IN THIS MODEL. IN OTHER WORDS...WE WILL BE HOLDING OFF ON ANY
INDICATION OF A TROPICAL ENTITY IN THE GULF UNTIL WE SEE A TREND
TOWARD THIS SOLUTION WHICH...BY THE WAY...DOES FIT THE CLIMATOLOGY
FOR LATE OCT IN THE ATLANTIC BASIN.

&&

.MARINE...WINDS AND SEAS WILL REMAIN LOW TODAY WITH WEAK HIGH
PRESSURE OVER THE WATERS. THIS HIGH WILL MOVE EAST AND THE PRESSURE
GRADIENT WILL TIGHTEN AS THE COLD FRONT APPROACHES TONIGHT. EXPECT
WINDS TO PICK UP AND SEAS TO BUILD AS THE COLD FRONT MOVES INTO THE
WESTERN WATERS AFTER MIDNIGHT ON SATURDAY AND REMAIN ELEVATED
THROUGHOUT THE REMAINDER OF THE WEEKEND. WITH THE SURFACE RIDGE
BUILDING DOWN THE EASTERN SEABOARD ON SATURDAY NIGHT...PERIODS OF
ADVISORY CONDITIONS WILL BE POSSIBLE SATURDAY AND SUNDAY NIGHTS WITH
WINDS IN THE 20 TO 25 KNOT RANGE AND SEAS BUILDING TO 6 TO 8 FEET
WELL OFFSHORE. SATURDAY/SUNDAY AFTERNOONS SHOULD FEATURE CAUTIONARY
CONDITIONS IN THE WAKE OF THE COLD FRONT. THE RIDGE SHOULD BUILD FAR
ENOUGH SOUTH TO ALLOW WINDS AND SEAS TO DIMINISH BELOW HEADLINE
CRITERIA BY TUESDAY AFTERNOON.

&&

.AVIATION...THIS TAF SET REPRESENTS A CONTINUATION OF OUR THINKING
ON THE TIMING OF THE NEXT FRONT AND A LESS PESSIMISTIC OUTLOOK" onClick="return popup(this, 'notes')">OUTLOOK FOR
THIS MORNING CONCERNING DEVELOPMENT OF LIFR CONDITIONS. CONDENSATION
PRESSURE DEFICIT CHARTS AND SREF PROBABILITIES ALL INDICATE A MUCH
LOWER CHANCE FOR FOG DEVELOPMENT OVER ERN AREAS (VLD) THAN OCCURRED
THU MORNING...AND THIS IS REFLECTED IN THE MOS. WE THEREFORE PULLED
WAY BACK IN THE VLD TERMINAL AND ARE NOW ONLY CALLING FOR MVFR VSBY
THERE. SIMILAR CONDITIONS ARE EXPECTED AT THE OTHER TERMINALS...WITH
THE GREATEST CONFIDENCE FOR MVFR VSBY SHIFTING TO AREAS W OF TLH FOR
THIS MORNING (PFN AND DHN). WE INCLUDED PROB30 GROUPS FOR AFTERNOON
SHOWERS AND VFR CEILINGS OF 4-5 KFT AT DHN AND ABY...WITH TEMPOS FOR
THE EVENING HOURS WHEN FROPA OCCURS. FURTHER SE...LOOK FOR RAIN
CHANCES TO HOLD OFF UNTIL AFTER 00Z.

&&

.FIRE WEATHER...WE ARE LOOKING FOR 2-3 HOUR DURATIONS OF RH AOB 35
PERCENT THIS AFTERNOON OVER ERN PORTIONS OF THE FL BIG BEND AND THIS
WILL BE MENTIONED IN THE DISCUSSION/REMARKS WITH NO WARNING
NECESSARY. DRIER AIR WILL QUICKLY RETURN TO THE AREA BEHIND THE
FRONT SAT AFTERNOON. IT APPEARS THAT DURATIONS WILL BE SUFFICIENT
FOR A WATCH TO BE POSTED FOR OUR FL ZONES FROM JEFFERSON COUNTY WWD.
SE AL WILL BE A CLOSE CALL FOR SAT. MON RH WILL BE DOWN AROUND 30
WITH 20-FT WINDS OVER 10 MPH. THE KBDI IS CURRENTLY ABOVE 500. IT IS
HARD TO TELL HOW FAR IT WILL DROP AFTER THE RAIN LATER TODAY AND
TONIGHT...SO BECAUSE OF THAT UNCERTAINTY...WE WILL POST A WATCH FOR
THOSE 5 COUNTIES AS WELL.

&&

.PRELIMINARY POINT TEMPS/POPS...
TALLAHASSEE  86  60  80  51  75 /   5  40   5   0   0
PANAMA CITY  83  63  78  58  77 /  10  50   0   0   0
DOTHAN       81  56  78  50  76 /  40  60   0   0   0
ALBANY       84  58  78  50  75 /  20  60   0   0   0
VALDOSTA     87  60  78  50  75 /   5  40  10   0   0
CROSS CITY   88  63  81  53  78 /   0  20  20   0   0

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
AL...FIRE WEATHER WATCH SATURDAY AFTERNOON FOR THE FOLLOWING ZONES:
     COFFEE...DALE...GENEVA...HENRY...HOUSTON.

GA...NONE.
FL...FIRE WEATHER WATCH SATURDAY AFTERNOON FOR THE FOLLOWING ZONES:
     BAY...CALHOUN...FRANKLIN...GADSDEN...GULF...HOLMES...INLAND
     WALTON...JACKSON...JEFFERSON...LEON...LIBERTY...WAKULLA...
     WASHINGTON.

GM...NONE.

&&

$$

AVIATION/LONG TERM/FIRE WEATHER...WOOL
REST OF DISCUSSION...GODSEY