Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 251157
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
557 AM CST THU DEC 25 2014

.UPDATE...
FOR 12Z AVIATION.

&&

.DISCUSSION...

LONGWAVE TROUGH AXIS IS SWINGING THROUGH THE AREA THIS
MORNING...AND TAKING MOST OF THE CLOUD COVER WITH IT. POST FRONTAL
CLOUDS ACROSS THE FAR NORTH WILL CONTINUE SHIFTING EAST. WITH THE
BACK EDGE OF THE CLOUD DECK NOW ACROSS CENTRAL MS...MOSTLY CLEAR
SKIES ARE EXPECTED LATER THIS MORNING. FOR CHRISTMAS DAY AND
CHRISTMAS NIGHT...HIGH PRESSURE WILL SHIFT ACROSS THE AREA AS
UPPER LEVEL RIDGING BUILDS IN FROM THE SOUTHEAST. THIS WILL KEEP
CONDITIONS DRY AND SEASONAL. HIGHS TODAY WILL BE IN THE LOW TO MID
50S...AND LOWS TONIGHT IN THE 30S.

A LONGWAVE TROUGH WILL AMPLIFY OVER THE WESTERN CONUS TODAY AND
FRIDAY AS IT SLOWLY MOVES EAST. MID AND UPPER LEVEL SOUTHWESTERLY
FLOW WILL GRADUALLY BRING MOISTURE BACK TO THE REGION WITH CLOUD
COVER RETURNING BY FRIDAY AFTERNOON. A SERIES OF IMPULSES ROTATING
THROUGH THE TROUGH WILL TRACK FROM THE WESTERN GULF
NORTHEASTWARD. WITH CONTINUED MOIST FLOW AND THE ADDED LIFT
ASSOCIATED WITH THE SHORTWAVES...RAIN WILL RETURN TO CENTRAL
ALABAMA EARLY SATURDAY. MODELS ARE IN GOOD AGREEMENT THAT THE
WEEKEND WILL BE WET...ESPECIALLY ACROSS THE NORTH WHERE LOW LEVEL
CONVERGENCE ALONG A SLOW MOVING SURFACE FRONT WILL ALSO CONTRIBUTE
TO CONTINUED RAIN DEVELOPMENT. DESPITE THE PROLONGED RAIN
EVENT...RAINFALL TOTALS ARE CONSERVATIVE WITH AMOUNTS GENERALLY
AT AN INCH OR LESS OVER THE WEEKEND. INSTABILITY IS ALSO LIMITED
WITH LESS THAN 200J/KG ML CAPE. WILL INCLUDE A MENTION OF THUNDER
BUT WITH WIDESPREAD CLOUD COVER AND RAINFALL...ANY SEVERE THREAT
LOOKS MINIMAL.

THE FRONT FINALLY CLEARS THE AREA ON MONDAY...AND A FEW DRY OR
MOSTLY DRY PERIODS ARE EXPECTED TO BEGIN THE WEEK. BROAD CYCLONIC
FLOW PERSISTS OVER THE CONUS THROUGH AT LEAST MIDWEEK...AS THE
TROUGH AMPLIFIES AGAIN WEST OF THE ROCKIES. THE NEXT WAVE OF RAIN
WILL COME NEXT WED/THUR. ALTHOUGH A COLD RAIN WILL BE POSSIBLE FOR
SOME PERIODS...AIRMASS WILL BE TOO WARM FOR ANYTHING FROZEN.

14


&&

.AVIATION...
12Z TAF DISCUSSION.

CLOUD COVER HAS REALLY ERODED SINCE SUNSET LAST NIGHT. THIS
TYPICALLY IS NOT THE CASE POST FRONTAL...BUT PLENTY OF DRY AIR WAS
ADVECTING IN FROM THE WEST. THE LATEST FOG SATELLITE IMAGERY WAS
INDICATING SOME CLOUD REDEVELOPMENT NEAR BHM/EET/ASN/ANB. THESE
CLOUDS WERE NEAR AN UPPER LEVEL TROUGH THAT WAS SWINGING THROUGH
THE REGION. MEAN MOISTURE IN THIS AREA WAS A BIT HIGHER. WENT
AHEAD AND PUT PREVAILING VFR IN ALL LOCATIONS BUT ADDED TEMPO MVFR
CEILINGS FOR A FEW HOURS THIS MORNING UNTIL THE TROUGH SWINGS BY
OR WE START MIXING INTO THE DRIER AIR. ADDITIONALLY...WE HAVE
COOLED TO NEAR SATURATION AT THE SURFACE AND SOME PATCHY MVFR FOG
MAY BE AROUND FOR A HOUR OR SO. OTHERWISE...A SURFACE HIGH MOVE
WEST TO EAST OVER THE AREA THIS CHRISTMAS WITH LIGHT WINDS AND
LITTLE CLOUDS. ALTHOUGH MOISTURE BECOMES VERY SHALLOW...WILL
MONITOR FOR SOME BRIEF GROUND FOG TOWARD THE END OF THE PERIOD.

75

&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     51  30  56  39  58 /   0   0  10  10  70
ANNISTON    53  33  58  40  59 /   0   0   0  10  70
BIRMINGHAM  54  36  58  43  59 /   0   0  10  10  70
TUSCALOOSA  55  36  59  45  58 /   0   0  10  20  80
CALERA      54  35  58  44  58 /   0   0  10  10  80
AUBURN      54  37  57  44  59 /   0   0   0  10  70
MONTGOMERY  57  36  60  45  62 /   0   0  10  20  80
TROY        56  36  59  46  63 /   0   0  10  20  80

&&

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

&&

$$






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