FXUS64 KBMX 112146
AFDBMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
346 PM CST FRI DEC 11 2009
.DISCUSSION...
MOISTURE IS CONTINUING TO START ITS NORTHWARD PUSH THIS
AFTERNOON...AS SLEET HAS ALREADY BEEN REPORTED ACROSS PORTIONS OF
SOUTHERN MISSISSIPPI...SOUTHERN ALABAMA...AND THE FLORIDA PANHANDLE.
GENERAL THINKING REMAINS THE SAME AT THIS POINT FROM YESTERDAY
REGARDING THE WINTRY PRECIPITATION OUTLOOK FOR EARLY TOMORROW
MORNING. MODELS ARE GENERALLY IN AGREEMENT THAT THE PRECIPITATION
SHIELD WILL BE ALMOST TO A LINE FROM DEMOPOLIS...TO MONTGOMERY...TO
AUBURN BY 12Z SATURDAY MORNING...AND MOVE NORTHWARD INTO THE
REMAINDER OF THE FORECAST AREA BY 15Z. MENTIONING FROM THE PREVIOUS
DISCUSSION THIS MORNING...THE ADVECTION OF THE VERY DRY DEW POINTS
ACROSS NORTH GEORGIA AND THE CAROLINAS FROM THE HIGH PRESSURE TO OUR
NORTHEAST IS CONCERNING...AND WE WILL CLOSELY WATCH THE
SITUATION...ESPECIALLY ACROSS OUR EASTERN AND NORTHEASTERN
COUNTIES...FOR THE POSSIBILITY OF ENOUGH EVAPORATIONAL COOLING TO
LEAD TO SUBFREEZING TEMPERATURES AT THE SURFACE. THE GOOD NEWS IS
THAT THE CONDITIONS WILL NOT LAST LONG...AS TEMPERATURES WILL
QUICKLY RISE THROUGHOUT THE DAY. TEMPERATURES WILL ONLY RISE INTO
THE UPPER 30S TO LOWER 40S HOWEVER...WITH WIDESPREAD RAINFALL
ACROSS THE ENTIRE FORECAST AREA.
ANOTHER THREAT IN THE FORECAST PERIOD WILL BE HOW MUCH RAINFALL WE
WILL RECEIVE THROUGH THE DAY ON SUNDAY. THE SHORT RANGE ENSEMBLE
FORECAST WORST CASE SCENARIO GIVES US OVER FOUR INCHES OF RAINFALL
THROUGH SATURDAY NIGHT...BUT THE ENSEMBLE MEAN IS LESS THAN HALF OF
THAT AMOUNT. WITH FLASH FLOOD GUIDANCE VALUES AROUND 2 INCHES IN THE
NORTHERN PORTIONS OF THE FORECAST AREA...AND 3 INCHES OR MORE IN THE
SOUTH...IT WOULD TAKE THE WORST CASE SCENARIO FOR ISSUING A FLASH
FLOOD WATCH. GENERALLY THE ENTIRE AREA SHOULD SEE AT LEAST AN INCH
AND A HALF TO TWO INCHES THROUGH THE DAY ON SUNDAY.
WE GET A SHORT BREAK ON MONDAY BETWEEN SYSTEMS...BUT WILL SEE A WARM
SECTOR BEGIN TO SET UP DURING THE AFTERNOON AND EVENING HOURS ON
MONDAY AHEAD OF THE NEXT APPROACHING COLD FRONT. THE GFS AND ECMWF
MODELS ARE CURRENTLY THINKING DEW POINTS IN THE MID 60S...AND
TEMPERATURES RISING TO ALMOST 70 DEGREES IN SOME LOCATIONS. WITH
SHEAR STARTING TO INCREASE ACROSS THE AREA...WE COULD SEE SOME
STRONG THUNDERSTORMS ACROSS CENTRAL ALABAMA WHEN THE COLD FRONT
MOVES THROUGH ON TUESDAY NIGHT. GFS PRECIPITABLE WATER VALUES ON
MONDAY ARE NEAR 1.5 INCHES...WHICH IS ALMOST TWO STANDARD DEVIATIONS
ABOVE NORMAL FOR THIS TIME OF THE YEAR...SO WE WILL HAVE TO WATCH
FOR HEAVY RAINFALL WITH THIS SYSTEM AS WELL.
TEMPERATURES COOL QUICKLY BEHIND THE FRONT ON WEDNESDAY...AND BELOW
NORMAL TEMPERATURES ARE IN THE CARDS FOR LATE NEXT WEEK.
56/GOGGINS
&&
AVIATION...18Z TAF DISCUSSION.
AN ACTIVE SOUTHERN BRANCH JET STREAM WILL KEEP A STEADY STREAM OF
MID AND HIGH LEVEL CLOUDINESS OVER THE AREA THROUGH MIDNIGHT
TONIGHT. WITH CEILINGS GRADUALLY LOWERING TO AROUND 5000 FEET.
SURFACE WINDS WILL REMAIN RATHER LIGHT FROM 030 TO 11 THROUGH 06Z
INCREASING TO BETWEEN 5 AND 10 KNOTS BY 12Z. EXPECT GRADUAL SHIFT
TOWARD THE EAST THROUGH THE PERIOD AS THE SURFACE HIGH SHIFTS
EASTWARD.
A MIXTURE OF RAIN AND SLEET WILL BEGIN NEAR MGM AND TOI AS EARLY AS
08Z AND BETWEEN 10 AND 12Z FARTHER NORTH AT TCL...BHM...EET AND ANB
AS A JET MAX SWINGS ACROSS THE AREA ENHANCING VERTICAL LIFT.
PRECIPITATION SHOULD TRANSITION TO ALL RAIN BY 14Z AS TEMPERATURES
CLIMB INTO THE UPPER 30S.
12/SIRMON
&&
.PRELIMINARY POINT TEMPS/POPS...
GADSDEN 27 39 39 54 45 / 20 100 100 60 0
ANNISTON 31 40 39 62 45 / 20 100 100 70 10
BIRMINGHAM 32 42 41 60 46 / 30 100 100 60 10
TUSCALOOSA 34 43 46 64 47 / 40 100 100 40 10
CALERA 33 42 43 60 47 / 40 100 100 50 10
AUBURN 33 39 40 61 47 / 40 100 100 60 20
MONTGOMERY 34 44 47 65 53 / 60 100 100 50 20
TROY 35 43 47 64 53 / 70 100 100 60 30
&&
.BMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
56/12
