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Area Forecast Discussion

971
FXUS64 KBMX 202147
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
347 PM CST SAT DEC 20 2014

.SHORT TERM...TONIGHT THROUGH MONDAY.

ANOTHER CLOUDY AND DAMP DAY ACROSS AREAS ALONG AND SOUTH OF I-59
AS THE CLEARING LINE HAS NOT MADE MUCH PROGRESSION. THE CLOUDS ARE
BEGINNING TO ERODE ALONG THE I-59 CORRIDOR AND THIS TREND WILL
LIKELY CONTINUE THROUGH THE EARLY EVENING HOURS. CLOUDS WILL
LIKELY LINGER ACROSS THE SOUTHERN HALF OF CENTRAL ALABAMA TONIGHT
DUE TO A STALLED OUT FRONTAL BOUNDARY. A WEAK UPPER IMPULSE MOVING
ACROSS THE NORTHERN GULF OF MEXICO COULD TRIGGER SOME LIGHT
SHOWERS SOUTH OF I-85 LATER TONIGHT AND KEPT A SLIGHT CHANCE OF
RAIN.

THE LOW CLOUDS OVER SOUTH CENTRAL ALABAMA WILL SHIFT NORTHWARD ON
SUNDAY AS THE LOW LEVEL FLOW BECOMES SOUTHEAST...AND DO NOT EXPECT
TO SEE MUCH SUNSHINE ON SUNDAY. THE AIR MASS ABOVE 850MB WILL NOT
UNDERGO MUCH CHANGE THROUGH SUNDAY NIGHT WITH RELATIVELY DRY AIR
ACROSS NORTH ALABAMA...WITH DEEPER MOISTURE CONFINED TO THE
IMMEDIATE GULF COAST. RAIN CHANCES WILL EXPAND NORTHWARD ON MONDAY
TO INCLUDE ALL OF CENTRAL ALABAMA...BUT RAIN CHANCES WILL REMAIN
ON THE LOW SIDE.


.LONG TERM...TUESDAY THROUGH SATURDAY.

A VIGOROUS UPPER LEVEL LOW WILL DROP SOUTHWARD FROM THE NORTHERN
PLAINS STATES AND DIG SOUTHWARD INTO TEXAS MONDAY NIGHT. THIS IS
BY FAR ONE OF THE MORE AMPLIFIED SYSTEMS THIS WINTER SEASON AND IT
WILL GENERATE A SOUTHERN SURFACE LOW THAT RAPIDLY DEEPENS AND
TRACKS NORTHEAST ACROSS ALABAMA AND TENNESSEE TUESDAY NIGHT.
DEEP SOUTHERLY FLOW WILL CREATE MUCH ABOVE NORMAL PRECIPITABLE
WATER PROFILES ACROSS ALABAMA TUESDAY AND TUESDAY NIGHT. WIDESPREAD
SHOWERS AND EMBEDDED THUNDERSTORMS WILL DEVELOP TUESDAY WELL AHEAD
OF THE SURFACE COLD FRONT. SURFACE DEWPOINTS IN THE LOWER 60S ARE
FORECAST TO ADVECT AS FAR NORTH AS THE I-20 CORRIDOR TUESDAY NIGHT
...AND DECENT MID LEVEL LAPSE RATES WILL CREATE ENOUGH INSTABILITY
TUESDAY NIGHT FOR CONVECTION. 0-6KM AND 0-1KM BULK SHEAR VALUES
ARE RELATIVELY HIGH AND CERTAINLY ENOUGH TO SUPPORT ROTATING
UPDRAFTS...AND STORM RELATIVE HELICITY VALUES ARE HIGH ENOUGH FOR
TORNADIC STORMS. THE PRIMARY LIMITING FACTOR WILL BE THE VERY
MOIST AIR MASS. WIDESPREAD SHOWERS ON TUESDAY COULD LIMIT INSTABILITY
AND SATURATED PROFILES WILL LIMIT UPDRAFT POTENTIAL. HOWEVER...COOL
SEASON SYSTEMS ARE NORMALLY HIGH SHEAR AND LOW INSTABILITY...AND
THIS SYSTEM IS VERY DYNAMIC AND STRENGTHENING AS IT CROSSES THE
MISSISSIPPI RIVER. THE MODELS ARE NOT IN GOOD AGREEMENT IN THE
PROGRESSION OF THE COLD FRONT. YESTERDAY THE GFS WAS FASTER THAN
THE ECMWF AND THEY HAVE FLIP FLOPPED TODAY.

THE COLD FRONT SHOULD BE NEAR THE ALABAMA AND GEORGIA STATE LINE
BY SUNRISE WEDNESDAY AND STRONG COLD AIR ADVECTION WILL ENSUE ON
WEDNESDAY. TEMPERATURES WILL LIKELY FALL WEDNESDAY MORNING...AND
STAY STEADY OR SLOWLY RISE WEDNESDAY AFTERNOON. THERE WILL BE
PLENTY OF WRAP AROUND MOISTURE ON WEDNESDAY AND EXPECT SCATTERED
LIGHT SHOWERS ACROSS THE NORTHERN HALF OF ALABAMA. THE CLOUDS WILL
CLEAR OUT CHRISTMAS EVENING AND CHRISTMAS DAY LOOKS GOOD WITH
MOSTLY CLEAR SKIES AND NEAR AVERAGE TEMPERATURES. A NORTHERN
STREAM SHORT WAVE TROF WILL PUSH A WEAK COLD FRONT TOWARDS ALABAMA
ON FRIDAY. A LINE OF SHOWERS ALONG THE FRONT COULD IMPACT CENTRAL
ALABAMA FRIDAY NIGHT AND SATURDAY.

58/ROSE

&&

.AVIATION...
18Z TAF DISCUSSION.

STUBBORN LOW CLOUDS ARE NOW EXPECTED TO PERSIST THROUGHOUT THE
REST OF THE DAY FOR MOST TERMINALS. WEAK LOW-LEVEL FLOW HAS
PREVENTED A LOT OF THE CLOUDS FROM MIXING OUT. THE ONLY TERMINALS THAT
HAVE AN OPPORTUNITY TO MIX OUT WILL BE KTCL, KBHM, AND KEET AS THE
BACK EDGE OF THE CLOUDS IS JUST OFF TO THE NORTHWEST. ELSEWHERE
THE CLOUDS WILL HANG AROUND THE REST OF THE DAY AND INTO THE
EVENING HOURS. THE CIGS COULD RISE A BIT BY THE AFTERNOON...BUT
LOWER ONCE AGAIN OVERNIGHT TONIGHT TO IFR OR LOW-END MVFR. THE
CLOUDS COULD LINGER THROUGH MUCH OF THE MORNING ON SUNDAY AS
WELL...AND HAVE KEPT MENTION OF CLOUDS IN THE FORECAST THROUGH THE
REMAINDER OF THE PERIOD. WINDS WILL REMAIN LIGHT AND VARIABLE THIS
AFTERNOON AND THROUGH THE OVERNIGHT.

56/GDG


&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     34  53  43  57  50 /  10  10  20  30  50
ANNISTON    37  55  46  58  51 /  10  20  30  30  40
BIRMINGHAM  38  56  46  60  54 /  10  10  20  30  40
TUSCALOOSA  37  59  46  61  53 /  10  10  20  30  40
CALERA      39  57  46  61  53 /  10  10  20  30  40
AUBURN      44  55  47  59  53 /  20  30  40  40  40
MONTGOMERY  45  59  48  65  55 /  20  30  40  30  40
TROY        46  57  49  64  56 /  20  40  40  30  40

&&

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

&&

$$







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