Area Forecast Discussion
Issued by NWS Birmingham, AL

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000
FXUS64 KBMX 231154
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
654 AM CDT TUE SEP 23 2014

.UPDATE...
FOR 12Z AVIATION.

&&

.DISCUSSION...

A NICE COOL FALL MORNING ACROSS CENTRAL ALABAMA WITH MOST LOCATIONS
IN THE 50S. ALREADY HAVE SEEN A FEW LOCATIONS TO THE NORTH OF
CENTRAL ALABAMA IN THE UPPER 40S AND WOULD EXPECT SOME OF THE COOLER
LOCATIONS ACROSS CENTRAL ALABAMA WILL DROP INTO THE UPPER 40S BEFORE
DAYBREAK. THE UPPER LEVEL TROUGH DIVING SOUTHEAST ACROSS THE
MID-MISSISSIPPI RIVER VALLEY YESTERDAY MORNING HAS SLOWED THIS
MORNING AND IS CLOSING OFF ALONG THE GEORGIA/SOUTH CAROLINA COAST.
IN ADDITION...WATER VAPOR IMAGERY INDICATES SUBSTANTIAL SUBSIDENCE
AND DRY AIR ACROSS THE SOUTHEAST IN THE WAKE OF THE UPPER LEVEL
TROUGH. THE 00Z BMX SOUNDING INDICATED SIGNIFICANT DRYING FROM THE
PREVIOUS LAUNCH WITH A PW VALUE OF 0.60 INCHES. FURTHER TO THE
NORTHWEST...AN UPPER LEVEL RIDGE IS IN PLACE ACROSS THE
MID-MISSISSIPPI RIVER VALLEY BUT IS BEGINNING TO FLATTEN AS A TROUGH
MOVES ACROSS THE NORTHERN ROCKIES AND NORTHERN PLAINS. AT THE
SURFACE...THE COLD FRONT IS NOW WELL TO THE SOUTH OF THE AREA IN THE
NORTHERN FLORIDA PANHANDLE. CURRENT IR SATELLITE IMAGERY INDICATES A
WEAK SURGE IN LOW LEVEL MOISTURE THAT HAS LED TO INCREASED CLOUD
COVER ACROSS SOUTHEASTERN PORTIONS OF THE FORECAST AREA. SURFACE
HIGH PRESSURE IS CENTERED OVER THE OHIO RIVER VALLEY ACCORDING TO
THE LATEST SURFACE ANALYSIS. OVERALL...THERE WILL ONLY BE MINOR
CHANGES TO THE UPPER LEVEL AND SURFACE PATTERN THROUGHOUT THE END OF
THE WORK WEEK. THE CLOSED LOW TO THE EAST WILL BEGIN TO WEAKEN AS
THE DE-AMPLIFYING RIDGE TRIES TO TAKE HOLD ACROSS THE SOUTHEAST. THE
SURFACE HIGH TO THE NORTHEAST WILL KEEP EASTERLY TO NORTHEASTERLY
FLOW AT THE SURFACE. MODELS INDICATE THERE COULD BE SOME MINOR
SURGES IN MOISTURE THAT COULD INCREASE CLOUD COVER ACROSS THE EAST
AND SOUTHEAST BUT TIMING IS RATHER UNCERTAIN. THE COOLEST
TEMPERATURES THROUGHOUT THE FORECAST PERIOD WILL OCCUR THIS MORNING
WITH DEWPOINTS SLOWLY CREEPING UP THROUGHOUT THE REMAINDER OF THE
WORK WEEK. TEMPERATURES WILL BE NEAR NORMAL FOR THIS TIME OF YEAR
WITH HIGHS IN THE LOW TO MID 80S AND LOWS IN THE UPPER 50S TO LOW
60S.

THE NEXT CHANCE OF RAIN IS EXPECTED OVER THE WEEKEND AS TROPICAL
MOISTURE MOVES NORTHWARD OUT OF THE NORTHWESTERN GULF OF MEXICO IN
ASSOCIATION WITH A SHORTWAVE TROUGH. THE UPPER LEVEL RIDGE IS
EXPECTED TO SHIFT TO THE EAST LATE IN THE WEEK AS A TROUGH MOVES OUT
OF NORTHERN MEXICO INTO THE NORTHWESTERN GULF. DEWPOINTS LATE IN THE
WEEK WILL RETURN TO THE MID TO UPPER 60S WITH MODELS INDICATING PW
VALUES OVER 2 INCHES. THESE VALUES WOULD BE NEAR THE 99TH PERCENTILE
FOR LATE SEPTEMBER. THE GFS AND ECMWF DIFFER A BIT ON TIMING AND
STRENGTH OF THE UPPER LEVEL TROUGH. IT APPEARS THAT THE MODELS ARE A
BIT SLOWER WITH THE MOISTURE AND HAVE DELAYED THE START OF
PRECIPITATION WITH ONLY SLIGHT CHANCES POPS ON SATURDAY. THE GFS
INDICATES A LEAD SHORTWAVE TROUGH MOVING JUST TO THE WEST OF THE
AREA ON SATURDAY WITH LITTLE TO NO PRECIPITATION. THEREFORE..WENT
AHEAD AND LOWERED POPS ON SATURDAY. BOTH THE GFS AND ECMWF INDICATE
SIGNIFICANT MOISTURE ADVECTION ON SUNDAY AND INCREASED POPS TO 50%
ACROSS THE AREA. THERE ARE SOME MORE MAJOR DIFFERENCES BEYOND THIS
POINT AS THE ECMWF CLOSES OFF THE TROUGH AND MOVES IT SLOWLY THROUGH
THE AREA WHILE THE GFS IS MORE PROGRESSIVE. REGARDLESS...IT LOOKS
WET FOR THE START OF NEXT WEEK WITH THE ECMWF HANGING ONTO HIGHER
RAIN CHANCES INTO THE MIDDLE OF THE WEEK. WITH THE INCREASED RAIN
CHANCES...KEPT TEMPERATURES A BIT LOWER THAN GUIDANCE WITH HIGHS
ONLY IN THE 70S.

05/MA


&&

.AVIATION...
12Z TAF DISCUSSION.

IFR CEILINGS HAVE DEVELOPED AT TOI...WITH MVFR CEILINGS NEAR MGM.
THESE CLOUDS WILL BEGIN MIXING AND RISE TO VFR OR NO CEILING BY
15-16Z. OTHERWISE...THE OTHER TERMINALS REMAIN VFR.

SURFACE HIGH PRESSURE TO THE NORTHEAST WILL KEEP AN EAST NORTHEAST
FLOW THROUGH THE PERIOD. SOME OF THE HIGHER RESOLUTION MODELS
INDICATE SOME ISENTROPIC LIFT OVER SOUTH GEORGIA THAT WILL
TRANSITION TO A MORE PRESSURE ADVECTION AND ISENTROPIC SURFACE
LIFTING THE NEXT 24 HOURS. THE OVERALL MOISTURE CONTENT WILL BE
HIGHEST SOUTHEAST NEAR TOI WITH DRIER CONDITIONS TO THE NORTHWEST.
A FEW CLOUDS MAY FLOAT AROUND DURING THE DAYLIGHT
HOURS...POTENTIALLY A BIT CLOSER TO CEILINGS SOUTH. EXPECT SOME
ADDITIONAL CLOUD COVER DEVELOPING LATE TONIGHT AGAIN SOUTH.
BELIEVE THE OVERALL MOISTURE CONTENT IS TOO DRY NORTH. ADDED
MENTION OF POTENTIAL MVFR CEILINGS AT TOI ATTM.

WINDS WILL BE 8-11KTS TODAY WITH A LIMITED GUST TO NEAR 16KTS
DECREASING TO AROUND 4 KTS OVERNIGHT.

NOTE...THE NATIONAL WEATHER SERVICE WILL BEGIN ISSUING SEASONAL
TERMINAL FORECASTS FOR THE TALLADEGA MUNICIPAL AIRPORT (KASN) IN
TALLADEGA...ALABAMA. THE FORECAST WILL BEGIN OCTOBER 5TH AT 00Z
AND LAST THROUGH AT LEAST THE 23RD OF OCTOBER.

75

&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     79  53  80  56  82 /   0   0   0   0   0
ANNISTON    78  55  79  59  82 /   0   0   0   0   0
BIRMINGHAM  80  57  80  61  82 /   0   0   0   0   0
TUSCALOOSA  83  58  84  60  85 /   0   0   0   0   0
CALERA      81  57  81  60  82 /   0   0   0   0   0
AUBURN      80  55  80  60  81 /   0   0   0  10  10
MONTGOMERY  82  59  83  61  83 /   0   0   0  10  10
TROY        80  58  81  59  82 /   0   0  10  10  10

&&

.BMX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$







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