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000
FXUS64 KBMX 222000
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
300 PM CDT WED MAY 22 2013

.DISCUSSION...

TODAY`S FORECAST IS BROUGHT TO YOU BY THE LETTERS MCS... AS IN
MESOSCALE CONVECTIVE SYSTEMS CAN REALLY MESS WITH A FORECAST.
SHOWERS AND THUNDERSTORMS HAVE BEEN VERY SLOW TO DEVELOP THIS
AFTERNOON ACROSS CENTRAL ALABAMA SINCE WIDESPREAD MID AND HIGH
CLOUDS LEFTOVER FROM THE NOW DEFUNCT OVERNIGHT MCS IN MISSISSIPPI
HAVE SLOWED THE RATE OF HEATING TODAY. AS OF 3 PM CDT... MANY
LOCATIONS ARE JUST NOW REACHING THEIR CONVECTIVE TEMPERATURES...
AND A FEW SHOWERS AND THUNDERSTORMS HAVE FORMED ALONG A SURFACE
TROUGH AND DIFFERENTIAL HEATING ZONE IN OUR NORTHEASTERN AREA AROUND
ANNISTON AND GADSDEN. BACK IN MISSISSIPPI PRECIP IS STRUGGLING TO
GET GOING ALONG/JUST AHEAD OF THE COLD FRONT DUE TO THOSE LEFTOVER
CLOUDS MENTIONED ABOVE. WITH DECENT LOW LEVEL MOISTURE IN PLACE AND
SBCAPE OF 1500 TO 2000 J/KG ACROSS THE EASTERN HALF OF THE AREA...
STILL THINK SOME SCATTERED DEVELOPMENT WILL OCCUR FOR A MAJORITY OF
CENTRAL ALABAMA THIS AFTERNOON AND EARLY EVENING AS A SHORTWAVE
TROUGH MOVING OVER WESTERN TENNESSEE GLANCES THE REGION TO THE
NORTH. LOOKING AT SEVERE POTENTIAL FOR THE REST OF THE AFTERNOON...
THE WIND SHEAR NEEDED TO ORGANIZE STORMS IS TOO WEAK... 30 KT OR
LESS. SO WHILE SOME STRONG STORMS WITH SMALL HAIL AND GUSTY WINDS
WILL BE POSSIBLE GIVEN THE INSTABILITY AND SURFACE COLD FRONT
APPROACHING FROM MISSISSIPPI... THINK THAT STORMS FOR CENTRAL
ALABAMA SHOULD REMAIN BELOW SEVERE LEVELS.

HAVE KEPT IN A CHANCE FOR SHOWERS AND A SLIGHT CHANCE FOR A
THUNDERSTORM TONIGHT FOR LOCATIONS ALONG AND SOUTHEAST OF THE
I-20/59 CORRIDOR. PRECIP CHANCES DECREASE BY THURSDAY MORNING... AND
HAVE ONLY KEPT IN SLIGHT CHANCE POPS FOR THE SOUTHEAST BEFORE 10 AM.
OTHERWISE EXPECT THURSDAY TO BE RAIN FREE ACROSS CENTRAL ALABAMA.

FRIDAY A SECONDARY SURGE OF COOLER AIR WILL MOVE INTO THE AREA AS
THE UPPER TROUGH ADVANCES TO THE EASTERN SEABOARD. THIS WILL BRING
OUR HIGHS DOWN BELOW AVERAGE FOR THE NORTHERN PORTIONS OF CENTRAL
ALABAMA. ALSO... MORNING LOWS ON SATURDAY LOOK TO BE QUITE COOL FOR
THIS TIME OF YEAR... UPPER 40S NORTH TO LOW/MID 50S SOUTH. BEHIND
THE DEPARTURE OF THE UPPER TROUGH... SURFACE HIGH PRESSURE WILL
SETTLE OVER THE SOUTHEAST FOR THE WEEKEND. BASED OFF THIS HIGH
PRESSURE MOVING IN AND THE SOMEWHAT DRIER AIR BEHIND THE
SECONDARY SURGE OF COOLER AIR FRIDAY... NOT EXPECTING PRECIP FOR
SATURDAY OR SUNDAY.

HOWEVER... WITH THE DEPARTURE OF THE UPPER TROUGH TO OUR EAST...
CENTRAL ALABAMA WILL BE PLACED IN NORTHWEST FLOW ALOFT FROM SATURDAY
THROUGH ABOUT NEXT TUESDAY. UNDER THIS SETUP AND GIVEN SUFFICIENT
MOISTURE... WE OFTEN GET MCS FEATURES MOVING FROM ARKANSAS/NORTHERN
MISSISSIPPI INTO THE AREA IN THE AFTERNOON/EVENING TIME FRAME. THE
12Z ECMWF IS HINTING AT THIS POSSIBILITY EACH AFTERNOON FROM
SATURDAY THROUGH TUESDAY. IT DOES KEEP THE BULK OF THE PRECIP
EITHER TO THE NORTH OR WEST OF CENTRAL ALABAMA... BUT IT IS
SOMETHING TO KEEP IN MIND. OF COURSE... THE GFS KEEPS THINGS DRY
FOR THE ENTIRE EXTENDED PERIOD WITH A STRONGER UPPER LEVEL RIDGE
IN PLACE AND THE DISTURBANCES ROUNDING THE CREST OF THE RIDGE TO
THE NORTH OF ALABAMA. IN KEEPING WITH THE PREVIOUS FORECAST
PACKAGE... HAVE KEPT POPS OUT OF THE FORECAST FROM FRIDAY THROUGH
NEXT WEDNESDAY. IF BOTH THE GFS AND ECMWF BEGIN TO AGREE ON A
SPECIFIC DAY (OR DAYS) FOR POSSIBLE MCS DEVELOPMENT... THEN POPS
MAY HAVE TO BE ADDED. BUT MCS FORMATION IN NORTHWEST FLOW IS
USUALLY VERY DIFFICULT FOR THE GLOBAL SCALE MODELS TO PICK UP
ON... ESPECIALLY THIS FAR OUT. SO ITS BASICALLY WAIT AND SEE.
REGARDLESS.... WEEKEND TEMPS LOOK VERY NICE IN THE MID TO UPPER
80S.

77/GLEASON

&&

.AVIATION...
18Z TAF DISCUSSION.

MOST MODELS HAVE BEEN TOSSED OUT THE WINDOW THIS AFTERNOON AS THEY
ARE STRUGGLING WITH THE MCV ACROSS THE GULF COAST AHEAD OF THE
COLD FRONT. CLOUDS HAVE REALLY KEPT THE WESTERN TWO-THIRD OF
CENTRAL ALABAMA INCLUDING BHM...EET...AND TCL STABLE THIS MORNING
AND DO NOT EXPECT TOO MUCH IN THE WAY OF THUNDERSTORM ACTIVITY AS
THE COLD FRONT MOVES THROUGH. MEANWHILE ANB...MGM AND TOI HAVE HAD
SOME CLEARING THIS MORNING. ALTHOUGH CLOUDS WILL BE WORKING INTO
MGM AND ANB VERY QUICKLY AND SHOULD LIMIT ACTIVITY THERE AS WELL.
REALLY TOI WOULD BE THE ONLY ONE AT A GREAT SHOT AT A
THUNDERSTORM SO I DID GO AHEAD AND THROW IN VCTS...BUT NOT
CONFIDENT ON THE OVERALL TIMING AS THE ACTIVITY REMAINS SCATTERED.

CURRENT RADAR SHOWS SOME LIGHT RETURNS APPROACHING BHM AND
EET...BUT REPORTS HAVE NOT BEEN OCCURRING AND TCL DID NOT RECEIVE
ANY RAIN WITH IT SO WILL JUST KEEP IN VCSH FOR THESE SITES NOW.

COLD FRONT WORK THROUGH THIS AFTERNOON...TONIGHT...BUT THINKING
THAT THE BEST MOISTURE WILL BE LIMITED...SO DID NOT GO WITH ANY
PREDOMINATE PERIOD FOR RAIN. AGAIN THUNDERSTORM ACTIVITY WILL BE
LIMITED. WILL SEND AMENDMENTS FOR ANY ORGANIZED THUNDERSTORM
ACTIVITY THIS AFTERNOON AS NEEDED.

OVERNIGHT WILL GO MORE PESSIMISTIC AND KEEP IN MVFR CEILINGS AS
THERE WILL STILL BE SOME MOISTURE AROUND BEHIND THE FRONT. ANOTHER
DISTURBANCE ROLLS THROUGH ON THURSDAY BUT SHOULD BE LIMITED TO MGM
AND TOI AFTER THIS TAF PERIOD.

16

&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     63  83  56  76  47 /  30  10  10   0   0
ANNISTON    64  84  58  77  49 /  30  10  10   0   0
BIRMINGHAM  64  84  59  77  51 /  30  10  10   0   0
TUSCALOOSA  63  87  60  80  51 /  30  10  10   0   0
CALERA      65  84  59  79  52 /  30  10  10   0   0
AUBURN      66  84  60  79  54 /  40  20  10   0   0
MONTGOMERY  67  88  62  83  54 /  40  20  10   0   0
TROY        67  88  62  83  52 /  40  20  10   0   0

&&

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

&&

$$

77/16