FXUS64 KHUN 292357 AAA
AFDHUN
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
557 PM CST SUN NOV 29 2009
.UPDATE...
FOR 00Z AVIATION DISCUSSION.
&&
.AVIATION.../00Z TAFS/
MVFR CONDITIONS WILL PERSIST THROUGH AT LEAST 30/18Z AS
PERIODS OF RA/SHRA IMPACT KMSL AND KHSV. A COLD FRONT WILL MOVE
INTO THE AREA BETWEEN 07-09Z BRINGING HEAVIER RA/SHRA FROM WEST TO
EAST REDUCING CEILINGS AND VISIBILITIES. BRIEF IFR CONDITIONS WILL
BE POSSIBLE ESPECIALLY JUST BEFORE AND JUST AFTER FRONTAL PASSAGE
ALTHOUGH LOW CONFIDENCE REMAINS WITH REGARDS TO TIMING. VFR
CONDITIONS AND NORTHWEST WINDS WILL DEVELOP ONCE THE FRONT PUSHES
THROUGH THE AREA AFTER 30/18Z.
&&
.DISCUSSION... /ISSUED 203 PM CST SUN NOV 29 2009/
A CLOUDY BUT MILD DAY TODAY ACROSS THE TENNESSEE VALLEY...BUT
CHANGES ARE ON THE WAY...AND IN FACT...CURRENT TEMPS MAY BE THE
WARMEST WE SEE FOR QUITE SOME TIME. RAIN IS PUSHING
IN...EARLY...TO THE NORTHWESTERN CORNER OF ALABAMA...BUT IT LOOKS
LIKE THE FORWARD PROGRESS IS BEGINNING TO SLOW AS IT MOVES INTO
THE DRIER AIR OVER OUR REGION.
SHORT TERM (TONIGHT THROUGH TUESDAY)...
RAIN IS A NEAR-CERTAINTY TONIGHT. EVEN IF THE CURRENT RAIN IS NOT A
FACTOR...ADDITIONAL SHOWERS WILL DEVELOP AS A COLD FRONT STILL OVER
MISSOURI AND ARKANSAS MOVES TOWARD THE AREA...AND A NRN STREAM UPPER
WAVE HELPS ENHANCE LIFT. WENT WITH 100 POPS OVER A LARGE PORTION OF
THE AREA. I DO THINK THERE IS LESS CERTAINTY OF RAIN BEFORE DAYBREAK
IN OUR EXTREME SOUTHEASTERN COMMUNITIES...AND SO WILL TAPER POPS TO
LIKELY IN THOSE AREAS. TEMPERATURES WILL NOT FALL MUCH...ONLY TO
AROUND 50...AND THEN PROBABLY RISE BACK TO THE MID 50S BY DAYBREAK.
THOSE MID 50S WILL BE THE HIGHS FOR THE DAY...AND THEN TEMPS WILL
FALL AT LEAST SEVERAL DEGREES UNTIL LATE AFTERNOON...WHEN THEY WILL
BEGIN TO PLUMMET. RAIN CHANCES ARE OBVIOUSLY DEPENDENT ON THE
FRONTAL LOCATION AT 12Z. WILL TAKE A BEST GUESS AND SHARPLY TAPER
POPS FROM SLIGHT CHANCE IN THE EXTREME NORTHWEST TO CATEGORICAL IN
THE SOUTHEASTERN COUNTIES. IF I FELT BETTER ABOUT THE FRONTAL TIMING
I COULD PROBABLY PINPOINT THINGS BETTER THAN I AM. BUT WITH A FRONT
THAT IS JUST BEGINNING TO MOVE...TRYING TO TIME IT IS PROBLEMATIC.
SKIES WILL CLEAR MONDAY NIGHT...AND WITH A DRIER AIRMASS IN PLACE...
TEMPERATURES WILL DROP TO NEAR FREEZING...WITH A FREEZE LIKELY IN
THE SHELTERED VALLEYS WHERE WINDS GO CALM. TUESDAY ALSO LOOKS DRY IN
BETWEEN SYSTEMS...WITH SOME HIGH CLOUDS AND HIGHS BETWEEN 55 AND 60.
WENT CLOSE TO THE MET FOR LOWS AND TOOK A BLEND FOR HIGHS.
EXTENDED (TUESDAY NIGHT THROUGH NEXT SUNDAY)...
AN UPPER LOW CURRENTLY CENTERED OVER BAJA CALIFORNIA WILL BE OUR
NEXT WEATHERMAKER BY MIDWEEK. TIMING IS UNCERTAIN SIMPLY BECAUSE OF
THE LOCATION OF THE LOW AND HOW QUICKLY...OR SLOWLY...IT WILL BE
ABLE TO EJECT. BELIEVE THE GFS IS EXHIBITING ITS FAST BIAS WITH THIS
SYSTEM...BUT ALSO BELIEVE THE NAM IS EXHIBITING ITS SLOW BIAS. WILL
THUS GO BETWEEN THE TWO...AND FAIRLY CLOSE TO THE SREF MEAN...FOR
POPS ON TUESDAY NIGHT.
WEDNESDAY LOOKS WET NO MATTER HOW YOU SLICE IT. THE DAY WILL BE
RATHER RAW AND BREEZY...WITH HIGHS ONLY IN THE MID 50S...AS THE SRN
STREAM LOW GETS ABSORBED INTO A DEVELOPING LONGWAVE TROUGH OVER THE
ERN CONUS. THEN...ADDITIONAL WRAPAROUND PRECIP IS LIKELY AS THE SFC
LOW DEEPENS IN RESPONSE TO THE LONGWAVE TROUGH ENERGY. MODEL
SOUNDINGS ACTUALLY SHOW POTENTIAL FOR A FLAKE OR TWO OF FROZEN
PRECIP TO MIX IN RIGHT AT THE END WEDNESDAY NIGHT...BUT SFC TEMPS
RIGHT NOW STILL LOOK TO BE AT/ABOVE 40...SO WILL NOT INCLUDE YET.
THE REST OF THE WORK WEEK...INTO THE WEEKEND...LOOK COLD AND DRY.
TEMPS MAY NOT GET MUCH ABOVE THE LOWER 40S ON THURSDAY...ALTHOUGH I
HEDGED A BIT AND WENT WITH MID 40S. A HARD FREEZE IS EXPECTED
THURSDAY NIGHT. PERSISTENCE LOOKS GOOD FOR TEMPS FRIDAY AND FRIDAY
NIGHT...BEFORE A WARMUP SATURDAY AS THE SFC HIGH MOVES EAST. HOW
MUCH OF A WARMUP IS IN QUESTION AS MODEL SOLUTIONS BEGIN TO
DIVERGE...SO WILL FOLLOW THE MEX GUIDANCE WITH THE CAVEAT THAT IT
MAY BE MUCH COLDER. NEXT SYSTEM APPROACHES FOR DAY 7/SUNDAY...AND I
WILL TAKE A COMPROMISE TIMING BETWEEN THE GFS AND ECMWF...LEAVING IN
JUST A SLIGHT CHANCE POP FOR SUNDAY.
FAST FACT...
IF HIGHS DO INDEED STAY IN THE 40S LATE THIS WEEK...IT WILL BE THE
FIRST DAY WITH HIGHS IN THE 40S SINCE APRIL 6TH. THIS IS THE FIRST
NOVEMBER WITHOUT A HIGH IN THE 40S SINCE 2004.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
AVIATION...KNS
DISCUSSION...JE/23
