National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS64 KBMX 121738
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
1138 AM CST THU DEC 12 2013

.DISCUSSION...

FORECAST APPEARS TO BE IN PRETTY GOOD SHAPE LATE THIS MORNING. SFC
RIDGING WILL CONTINUE TO BUILD IN FROM THE NW WITH COOL AND DRY
CONDITIONS EXPECTED ACROSS THE REGION. LOOK FOR SUNNY SKIES WITH
HIGHS IN THE LOW/MID 40S NORTH TO MID 50S SOUTHEAST.

THE ONLY ISSUE AT THE MOMENT IS THE POTENTIAL FOR FIRE WEATHER
CONCERNS THIS AFTERNOON. BASED ON CURRENT OBSERVATIONS AND
EXPECTED TRENDS...BELIEVE THERE MAY BE SEVERAL LOCATIONS THAT
COULD EXPERIENCE RH AT OR BELOW 25 PERCENT FOR UP TO 3 HOURS. ONE
OR TWO LOCALIZED AREAS COULD PERHAPS REACH THE FOUR HOUR CRITERIA
BUT CONFIDENCE IS JUST NOT HIGH ENOUGH TO WARRANT THE ISSUANCE OF
ANY FIRE WEATHER PRODUCTS AT THIS TIME. WILL CONTINUE TO MONITOR
CLOSELY. UPDATES ARE OUT.

19

&&

.AVIATION...
18Z TAF DISCUSSION.

VFR CONDITIONS EXPECTED THRU THE PERIOD AS SFC HIGH PRESSURE
BUILDS IN FROM THE NW. LOOK FOR NORTHERLY WINDS AROUND 10 KTS TODAY
BECOMING LIGHT/CALM OVERNIGHT. COULD SEE A FEW CIRRUS STREAMING IN
FROM THE WEST THIS EVENING AND OVERNIGHT.

19

&&

.PREV DISCUSSION...
/ISSUED 525 AM CST THU DEC 12 2013/

FAIRLY TRANQUIL WEATHER IS BEING OBSERVED ACROSS THE CONUS EARLY
THIS MORNING...WITH A LONGWAVE TROUGH CURRENTLY ACROSS THE EASTERN
CONUS AND A FAIRLY AMPLIFIED UPPER RIDGE ACROSS THE PACIFIC COAST
AND WESTERN CONUS. THE SUBTROPICAL JET STREAM CAN BE CLEARLY NOTED
ON IR SATELLITE IMAGERY SPREADING HIGH CLOUDS NORTHEASTWARD INTO
SOUTHERN NEW MEXICO AND WESTERN TEXAS. THAT SAME SUBTROPICAL JET
WILL BE THE MAIN CULPRIT FOR BRINGING IN WIDESPREAD RAINFALL AND
EMBEDDED STORMS INTO OUR NECK OF THE WOODS THIS WEEKEND.

IN TERMS OF THE WEATHER ACROSS CENTRAL ALABAMA TODAY...SURFACE HIGH
PRESSURE OF 1040MB THAT`S CURRENTLY CENTERED ACROSS MISSOURI AND
ILLINOIS WILL SINK SOUTHEASTWARD TODAY. A SECONDARY COLD FRONT HAS
ALREADY MOVED THROUGH THE CWA PUSHING IN A REINFORCING SHOT OF
COOLER AIR. IN FACT...THAT COOLER AIR WILL BE FELT TODAY EVEN WITH
FULL SUNSHINE. THICKNESSES ARE SUPPORTING HIGHS TODAY RANGING FROM
THE LOWER 40S NORTH TO THE MID 50S SOUTH. ANOTHER CHILLY NIGHT WILL
BE IN STORE TONIGHT WITH WIDESPREAD FREEZING CONDITIONS AS THE
SURFACE HIGH MOVES OVER THE STATE.

AS MENTIONED EARLIER...THE SUBTROPICAL JET AT 300MB WILL BEGIN TO
PUSH INTO THE SOUTHEASTERN U.S. FRIDAY EVENING AND THROUGH THE DAY
ON SATURDAY. AS THE 115+ KNOT JET ROUNDS THE BASE OF THE DEVELOPING
TROUGH DIGGING ACROSS OKLAHOMA AND NORTHERN TEXAS...PLENTY OF UPPER
LEVEL DIVERGENCE WILL BE ONGOING ACROSS CENTRAL ALABAMA. THE
SOUTHWESTERLY FLOW ALOFT SHOULD BE ABLE TO SPREAD WIDESPREAD CLOUDS
ACROSS THE AREA BY FRIDAY AFTERNOON. I WENT AHEAD AND ADDED IN A
SLIGHT CHANCE OF LIGHT RAIN ACROSS THE FAR WESTERN COUNTIES FRIDAY
EVENING...BUT AS WE HAVE ALREADY SEEN THIS FALL SEASON THE PRECIP
HAS ALWAYS COME IN MUCH EARLIER THAN MODELS HAVE ANTICIPATED. WE MAY
HAVE TO RAISE POPS A BIT ACROSS THE AREA MORE ON FRIDAY EVENING OVER
THE NEXT FEW SHIFTS. SURFACE CYCLOGENESIS IS EXPECTED TO OCCUR
ACROSS NORTHERN LOUISIANA BY EARLY SATURDAY MORNING...SPREADING
WIDESPREAD GULF MOISTURE NORTHWARD.

TEMPERATURES WILL BE ON THE INCREASE AFTER MIDNIGHT FRIDAY NIGHT AND
INTO SATURDAY MORNING AS THE SURFACE LOW TRACKS ACROSS SOUTHWESTERN
ALABAMA WITH WIDESPREAD RAINFALL ONGOING. I HAVE OPTED TO LEAVE
MENTION OF THUNDER IN THE FORECAST FOR NOW ON SATURDAY AS WE COULD
HAVE SOME ELEVATED INSTABILITY...ESPECIALLY ACROSS OUR SOUTHERN
COUNTIES. MAINLY ALL RAIN IS EXPECTED HOWEVER...WITH RAINFALL
AMOUNTS GENERALLY RANGING AROUND AN INCH FOR THE ENTIRE AREA. THIS
WILL BE A FAIRLY QUICK HITTING SYSTEM...SO WE SHOULDN`T HAVE TOO
MANY PROBLEMS IN TERMS OF FLOODING. AS THE SURFACE LOW TRACKS ACROSS
FAR SOUTHERN ALABAMA BY SUNDAY THE DRIER AND COOLER AIR WILL FILTER
IN FROM THE NORTHWEST. LINGERING RAINFALL ACROSS THE SOUTHEASTERN
COUNTIES SHOULD COME TO AN END BY NOON ON SUNDAY WITH TEMPERATURES
DROPPING THROUGHOUT THE DAY. IT COULD BE HARD FOR TEMPERATURES TO
WARM INTO THE LOWER 40S ACROSS OUR NORTHERN COUNTIES AND LOWER 50S
SOUTHEAST SUNDAY AFTERNOON WITH A DECENT NORTHWEST WIND AROUND 10
KNOTS. SO DEFINITELY A COLD DAY LOOKS TO BE IN STORE ON SUNDAY.

THE LONG TERM PERIOD FOR NEXT WEEK THEN BECOMES CHALLENGING WITH THE
OVERALL PATTERN NOT BEING HANDLED VERY WELL BY THE LONG-RANGE
GUIDANCE. HOWEVER...THERE ARE SOME TRENDS THAT I CAN HANG MY HAT
ON. THE OPERATIONAL GFS IS REALLY HITTING HARD ON A REINFORCING
SHOT OF COLD AIR BY WEDNESDAY EVENING AND INTO THURSDAY AND A DEEP
TROUGH ACROSS THE EASTERN CONUS. IF YOU LOOK AT OTHER MODEL
GUIDANCE...THE ECMWF AND CMC DEVELOP A MUCH LESS AMPLIFIED TROUGH
AND RETURN THE PATTERN ACROSS THE COUNTRY TO MORE ZONAL.
ALSO...LOOKING AT THE GFS ENSEMBLE MEMBERS...THERE ARE AT LEAST 4
MEMBERS THAT ARE MORE IN LINE WITH THE OPERATIONAL ECMWF IN EITHER A
ZONAL FLOW AT 500MB OR RIDGING OVER THE EASTERN CONUS. THAT ALONE
REALLY STARTS TRENDING MY FORECAST AWAY FROM THE GFS AND GFS MOS
GUIDANCE...AND THAT THE CURRENT GFS RUN IS CERTAINLY AN OUTLIER AT
THIS POINT. I HAVE STARTED TRENDING MY FORECAST TOWARD THE MORE
AMPLIFIED SOLUTION IN THE LONG TERM WITH MILDER TEMPS AND SOUTHERLY
WINDS AT THE SURFACE IN THE GRIDS TO TRY AND GET AHEAD OF THE GAME.
LOOKING AT THE NEWEST 06Z RUN OF THE GFS...IT`S TRYING TO BECOME
MORE IN LINE WITH THE ECMWF WITH A VERY WARM PERIOD IN STORE LATE
NEXT WEEK WITH A POTENT TROUGH DIGGING IN THE MIDDLE OF THE COUNTRY.
WE`LL SEE IF THOSE TRENDS CONTINUE IN THE COMING DAYS.

56/GDG

&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     46  25  51  41  56 /   0   0   0 100 100
ANNISTON    46  27  52  42  57 /   0   0   0  90 100
BIRMINGHAM  47  28  51  43  58 /   0   0  10 100 100
TUSCALOOSA  50  27  53  44  59 /   0   0  20 100 100
CALERA      48  29  54  44  60 /   0   0  10 100 100
AUBURN      52  30  53  45  61 /   0   0   0  50 100
MONTGOMERY  55  29  58  45  63 /   0   0   0  70 100
TROY        56  28  59  47  65 /   0   0   0  30 100

&&

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

&&

$$