074
FXUS64 KHUN 092046
AFDHUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
246 PM CST MON NOV 9 2009
DISCUSSION
FOR THIS FORECAST PACKAGE...ALL EYES ARE LOOKING SOUTH TOWARD THE
GULF COAST AND THE WEAKENING TROPICAL DISTURBANCE THAT WAS ONCE
HURRICANE IDA. LATEST VISIBLE SATELLITE IMAGERY AND SLP ANALYSIS
SHOWS THE CENTER OF THE CIRCULATION ABOUT DUE SOUTH OF THE
ALABAMA/MISSISSIPPI STATE LINE...BUT STILL WELL OFFSHORE FROM THE
COASTAL BEACH COMMUNITIES OF THE NORTHERN GOMEX. FORECAST FOR
TONIGHT AND TOMORROW HINGES GREATLY UPON THE ULTIMATE TRACK OF THIS
STORM AS IT MAKES ITS EXTRATROPICAL TRANSITION AND IS SWEPT UP
BY/INTERACTS WITH AN APPROACHING MID LEVEL TROUGH.
12Z BMX SOUNDING /ALONG WITH HSV/MSL NAM/GFS BUFR SOUNDINGS SUGGEST
A GOOD TONGUE OF DRY AIR IN THE LOW LEVELS...AND VIRGA ACROSS THE
CENTRAL PORTIONS OF ALABAMA SUPPORTS THIS...SO HAVE TRIMMED BACK THE
POPS FOR THIS EVENING /ESPECIALLY NORTH OF THE TENNESSEE RIVER/ AND
INSTEAD ADDED SOME ISOLATED SPRINKLES. THESE SHOULDN'T ADD UP TO
MUCH...AND THE REAL ACTION BEGINS TONIGHT AS THE LOW CONTINUES
TOWARD SHORE. RAIN CHANCES WILL INCREASE AFTER MIDNIGHT...AND WILL
BE MAXIMIZED FOR THE SOUTHEASTERN PORTIONS OF THE CWFA TOWARD THE
EARLY MORNING HOURS. THE GFS BRINGS THE PRECIPITATION SHIELD FARTHER
NORTH THAN THE NAM...BUT BELIEVE IT MIGHT BE JUST A BIT OVERDONE
WITH THE PRECIPITATION AS BOTH THE NAM AND GFS DEFORMATION BANDS AND
BEST ISENTROPIC ASCENT ARE MAXIMIZED WELL SOUTH OF OUR FORECAST
AREA. THAT SAID...BY TUESDAY AFTERNOON...STILL LOOKING FOR
WIDESPREAD 1-2 INCHES OF RAINFALL ACROSS PORTIONS OF
MARSHALL/DEKALB/JACKSON COUNTIES...WITH ISOLATED HIGHER AMOUNTS OF 2
TO 4 INCHES. WEST OF THE I-65 CORRIDOR...PRECIPITATION TOTALS WILL
BE MUCH MORE SCANT. THE MIDNIGHT SHIFT OPTED TO HOIST A FLASH FLOOD
WATCH FOR NORTHEASTERN ALABAMA FROM LATE TONIGHT THROUGH TUESDAY
AFTERNOON...AND GIVEN THE CURRENT FORECAST THINKING...SEE NO REASON
TO MAKE ANY SPATIAL CHANGES ATTM. THE ONLY TWEAKING POSSIBLY NEEDED
IS TO PUSH BACK THE START TIME OF THE WATCH...AND ULTIMATELY THAT
MAY HAPPEN IF THE DRY AIR IN THE LOW LEVELS SLOWS THE NORTHWARD
PROGRESSION OF PRECIPITATION THIS EVENING.
OTHER CONCERN SURROUNDING IDA INVOLVES POSSIBLE GUSTY NORTHEAST
WINDS LATE TONIGHT INTO TOMORROW. WITH THE CENTER OF THE LOW
REMAINING WELL SOUTH OF HERE...BEST LOW LEVEL JET AND WIND SHEAR
WILL CORRESPONDINGLY SET UP SOUTH OF HERE...BUT STILL COULD SEE SOME
GUSTS TO 35 KT ACROSS THE HIGHER TERRAIN....WITH SUSTAINED WINDS
AROUND 10 TO 20 POSSIBLE ACROSS MUCH OF THE CWFA.
PRECIPITATION WILL END FOR ALL BUT EXTREME NORTHEAST ALABAMA AND
THE EASTERN PORTIONS OF SOUTHERN MIDDLE TENNESSEE BY TUESDAY
EVENING...WITH A LARGES AREA OF HIGH PRESSURE BUILDING INTO THE
TENNESSEE VALLEY THOUGH THE REMAINDER OF THE WORK WEEK. THE
GFS/ECMWF HAVE BACKED OFF ON THE COLD FRONT THAT WAS PROGGED TO
TRACK THROUGH THE CWFA OVER THE WEEKEND. DROPPED POPS INTO SLIGHT
CHANCE THROUGH THE PERIOD AS BOTH GFS/ECMWF INDICATE FRONT MAY NOT
ARRIVE UNTIL THE MIDDLE OF NEXT WEEK.
PRELIMINARY POINT TEMPS/POPS
HUNTSVILLE 55 67 50 65 44 / 60 70 10 0 0
SHOALS 53 69 49 67 43 / 40 40 0 0 0
VINEMONT 55 66 50 65 43 / 80 80 10 0 0
FAYETTEVILLE 53 66 47 64 41 / 40 60 10 0 0
ALBERTVILLE 53 63 47 65 41 / 90 100 20 0 0
FORT PAYNE 52 62 49 65 41 / 90 100 30 0 0
HUN WATCHES/WARNINGS/ADVISORIES
AL...FLASH FLOOD WATCH FROM MIDNIGHT CST TONIGHT THROUGH TUESDAY
AFTERNOON FOR THE FOLLOWING ZONES: DEKALB...JACKSON...MARSHALL.
TN...NONE.
JLL
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