Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 242037
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
337 PM CDT THU APR 24 2014

.DISCUSSION...

WARM WEATHER CONTINUES TODAY WITH TEMPERATURES IN THE 80S ACROSS
MOST IF NOT ALL OF CENTRAL ALABAMA. LOOKING AT THE INFRARED
SATELLITE...STORMS CONTINUE ACROSS ARKANSAS ALONG A WARM FRONT WITH
THUNDERSTORMS DEVELOPING ALONG A COLD FRONT/DRYLINE BACK ACROSS
OKLAHOMA. WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL TROUGH
PROGRESSING EASTWARD ACROSS THE CENTRAL AND SOUTHERN PLAINS.
CONVECTIVE ACTIVITY SO FAR HAS BEEN RATHER MEAGER BUT SHOULD PICK UP
IN INTENSITY AS THE WARM SECTOR RECOVERS AND DEWPOINTS PUSH UP INTO
THE MID-60S. A SLIGHT RISK IS IN PLACES FOR THE NORTHWESTERN CORNER
OF THE FORECAST AREA. THE LOSS OF DAYTIME HEATING WILL BE THE MAIN
LIMITING FACTOR BUT HI-RES MODELS INDICATE MUCAPE VALUES AROUND
500-1000 J/KG. 0-6 KM BULK SHEAR WILL BE ON THE ORDER OF 50 TO 60
KTS. THEREFORE...THERE WILL BE ENOUGH DEEP LAYER SHEAR TO MAINTAIN
UPDRAFTS. LOW LEVEL SHEAR IS NOT OVERLY IMPRESSIVE AND WITH THE
NOCTURNAL NATURE OF THE CONVECTION...THE STORMS WILL MOST LIKELY BE
SLIGHTLY ELEVATED. THEREFORE...THE MAIN THREAT WILL BE DAMAGING WIND
GUSTS. THE TIMING WILL BE FROM 9 PM TONIGHT UNTIL 3 AM IN THE MORNING
WITH THE THREAT AREA ALONG AND NORTH OF A REFORM...TO FAYETTE...TO
DOUBLE SPRINGS LINE. MODELS OVER THE LAST DAY OR SO HAVE BEEN MORE
IMPRESSIVE WITH THE TOUGH AND HI-RES MODELS SHOW THAT THE CONVECTION
WILL HOLD TOGETHER INTO THE NORTHWESTERN PORTIONS OF THE FORECAST
AREA WITH THE CONTINUED DEEP LAYER SHEAR AND MODEST CAPE VALUES. THE
THREAT REMAINS LOW AND EXPECT ONLY AN ISOLATED SEVERE STORM OR TWO
AT MOST.

THE COLD FRONT ASSOCIATED WITH THE UPPER LEVEL TROUGH WILL MOVE
THROUGH CENTRAL ALABAMA EARLY IN THE DAY ON FRIDAY AND STALL JUST TO
THE SOUTH OF THE FORECAST AREA. THE UPPER LEVEL TROUGH WILL PULL OFF
TO THE NORTHEAST QUICKLY LATE TONIGHT INTO EARLY TOMORROW AND EXPECT
SHOWERS AND THUNDERSTORMS WILL REALLY BEGIN TO DIMINISH IN COVERAGE
AND INTENSITY LATE TONIGHT AND INTO EARLY TOMORROW MORNING.
PRECIPITATION COVERAGE WILL BE LIMITED TO THE NORTHEAST DURING THE
DAY TOMORROW AND ONLY HAVE A SLIGHT CHANCE FOR PRECIPITATION DURING
THE MORNING. EXPECT MOST OF THE DAY FRIDAY WILL BE DRY WITH
TEMPERATURES IN THE UPPER 70S TO LOW 80S WITH EXTREMELY WEAK COLD
AIR ADVECTION BEHIND THE FRONT.

TEMPERATURES WILL REALLY GO UP OVER THE WEEKEND. THE WARM FRONT WILL
WASH OUT AS A NEW WARM FRONT BECOMES ESTABLISHED ACROSS THE OHIO
RIVER VALLEY. SOUTHERLY FLOW AT THE SURFACE AND HIGHER UPPER LEVEL
HEIGHTS WILL PUSH TEMPERATURES UP INTO THE MID 80S EACH AFTERNOON.
DUE TO THE STRONG RIDGE...EXPECT A CAP WILL BE IN PLACE AND NOT
EXPECTING ANY CONVECTION TO FORM SATURDAY AFTERNOON. THE RIDGE
BEGINS TO BREAKDOWN LATE SUNDAY AS A POTENT UPPER LEVEL LOW SPINS
ACROSS THE CENTRAL PLAINS. A COUPLE OF THE MODELS SUGGEST A MCS
WILL FORM ALONG THE MISSISSIPPI RIVER AND PROGRESS TO THE EAST AND
DIE ALONG THE AL/MS STATE LINE. DUE TO THIS...CONTINUED HIGH CHANCES
POPS ACROSS THE NORTHWEST. JUST BEYOND THIS TIMEFRAME IS WHEN THINGS
BEGIN TO GET REALLY INTERESTING ACROSS CENTRAL ALABAMA

WITH EACH MODEL RUN...THE WEATHER SITUATION LOOKS MORE AND MORE
CONCERNING FOR MONDAY AFTERNOON INTO POSSIBILITY WEDNESDAY MORNING.
THE BIG WEATHER STORY WILL REMAIN TO BE THE CLOSED UPPER LEVEL LOW
OVER THE CENTRAL PLAINS EARLY NEXT WEEK. MULTIPLE SHORTWAVE TROUGHS
WILL ROTATE AROUND THIS CLOSED LOW PROVIDING CENTRAL ALABAMA WITH
MULTIPLE SHOTS FOR SEVERE WEATHER. UPPER LEVEL HEIGHT FALLS BEGIN TO
TAKE PLACE MONDAY AFTERNOON AS THE FIRST WAVE ROTATES AROUND THE
CLOSED LOW. TEMPERATURES WILL WARM INTO THE 80S ON MONDAY WITH
SBCAPE VALUES REACHING 1000-2000 J/KG WITH THE HIGHEST INSTABILITY
JUST TO THE WEST OF THE FORECAST AREA. THE FIRST WAVE IS NOT
EXPECTED TO ARRIVE UNTIL LATER IN THE DAY AND INTO THE OVERNIGHT
HOURS...THEREFORE...INSTABILITY VALUES WILL DECREASE SOME BUT MODELS
ARE STILL INDICATING AROUND 1000 J/KG OF SBCAPE DURING THE OVERNIGHT
HOURS. THE LOW LEVEL JET WILL INTENSIFY DURING THE OVERNIGHT HOURS
TO AROUND 45-55 KTS THIS WILL BE SUFFICIENT ENOUGH TO RAISE THE 0-1
KM SRH TO AROUND 200-300 M2/S2. THE DEEP LAYER SHEAR WILL BE ON THE
ORDER OF 40-50 KTS AND SHOULD BE ENOUGH TO MAINTAIN UPDRAFT
INTENSITY. ALL MODES OF SEVERE WEATHER WILL BE POSSIBLE BASED ON THE
CURRENT SEVERE WEATHER PARAMETERS. THIS FIRST ROUND WILL BE WELL
AHEAD OF THE SURFACE FRONT AND ANOTHER ROUND OF SEVERE WEATHER IS
FORECAST BY BOTH THE GFS AND ECMWF. MODELS INDICATE THERE COULD BE A
BRIEF BREAK TUESDAY MORNING AS THE LOW LEVEL JET LIFTS OUT AND THE
FIRST SHORTWAVE TROUGH LIFTS OFF TO NORTHEAST. THE SECOND ROUND IS
EXPECTED TUESDAY AFTERNOON INTO TUESDAY NIGHT AS ANOTHER SHORTWAVE
TROUGH ROTATES THROUGH THE BROAD CLOSED LOW. THE SEVERE WEATHER
PARAMETERS WILL BE VERY SIMILAR. THE ONLY DIFFERENCE IS THAT THE
DEEP LAYER 0-6 KM SHEAR IS FORECAST TO BE A BIT STRONGER WITH THE
SECOND ROUND. AGAIN...ALL MODES OF SEVERE WEATHER WILL BE POSSIBLE
WITH THIS SECOND ROUND AS WELL. MODELS HAVE BEEN FAIRLY CONSISTENT
AND CONFIDENCE CONTINUES TO INCREASE IN THE SEVERE WEATHER POTENTIAL
FOR MONDAY INTO TUESDAY. THERE ARE STILL SEVERAL QUESTIONS THAT
REMAIN REGARDING THE POTENTIAL EVENT. HOW WILL THE FIRST ROUND
AFFECT THE SECOND? HOW WILL THE TIMING WORK OUT? WILL BOTH ROUNDS BE
A NOCTURNAL EVENT OR HAPPEN DURING THE DAY? AT THIS TIME...IT LOOKS
LIKE BOTH ROUNDS COULD BE DURING THE OVERNIGHT HOURS. PLEASE PREPARE
AND BE READY FOR THIS EVENT. A TEMPORARY SOLUTION IS IN PLACE FOR
THE NWR TRANSMITTER IN BIRMINGHAM PLEASE SEE THE LATEST PNS FOR THE
MOST UP TO DATE INFORMATION. PLEASE HAVE YOUR SEVERE WEATHER PLAN
READY AS WE HEAD INTO EARLY NEXT WEEK.

05/MA


&&

.AVIATION...
18Z TAF DISCUSSION.

CU FIELD DEVELOPING THIS AFTERNOON WILL SPREAD ACROSS ALL TERMINALS
WITH CIGS AROUND 4KFT. OTHERWISE SOUTHERLY WINDS CONTINUE AROUND
5-8KTS. CONDITIONS WILL REMAIN VFR UNTIL TONIGHT. THERE IS ENOUGH
WEAK LOW LEVEL LIFT TO INCLUDE MVFR CIGS JUST AHEAD OF A BROKEN LINE
OF SHOWERS. WILL NEED TO WATCH NEAR TERM GUIDANCE AND SATELLITE
TRENDS THIS EVENING...AS LOW CLOUDS MIGHT BE QUICKER TO SPREAD
NORTHWARD. HAVE INCLUDE SHRA AT NORTHERN TERMINALS. CANNOT RULE OUT
A TS...BUT CONFIDENCE IS LOWER ON TS COVERAGE. LOW CIGS WILL
CONTINUE AFTER SHOWERS MOVE OUT OF THE AREA...WITH WEST TO NORTHWEST
WINDS INCREASING TO 10-13KTS.

MOISTURE AND FORCING IS LOWER ACROSS TOI AND MGM...AND WILL HOLD OFF
ON ANY MENTION OF SHRA. IF SHOWERS WERE TO OCCUR THAT FAR SOUTH, IT
WOULD BE AFTER 12Z.

14

NOTE...THE NATIONAL WEATHER SERVICE IS NOW ISSUING SEASONAL
TERMINAL FORECASTS FOR THE TALLADEGA MUNICIPAL AIRPORT (KASN) IN
TALLADEGA...ALABAMA. THE FORECASTS WILL BE ISSUED THROUGH AT LEAST
MAY 8TH 00Z. DUE TO THE LIMITED AVAILABILITY OF OBSERVATIONS...
KASN TAF WILL HAVE AMD NOT SKED APPENDED TO THE END OF THE FORECAST.


&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     60  77  48  82  56 /  70  20   0  10  10
ANNISTON    59  78  49  83  57 /  50  20   0  10  10
BIRMINGHAM  61  79  50  84  60 /  60  10   0  10   0
TUSCALOOSA  60  80  49  84  60 /  50  10   0  10  10
CALERA      61  79  52  83  61 /  30  10   0  10  10
AUBURN      58  79  53  81  60 /  10  20   0  10  10
MONTGOMERY  61  82  54  85  61 /  10  10   0  10  10
TROY        59  83  53  85  60 /  10  10   0  10  10

&&

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

&&

$$







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