Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 231758 AAB
AFDBMX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BIRMINGHAM AL
1158 AM CST SUN NOV 23 2014

.UPDATE...
AVIATION DISCUSSION

&&

.DISCUSSION...

UPDATED FORECAST TO REFLECT CURRENT RADAR AND TEMP/DEWPOINT TRENDS.
WIDESPREAD SHOWERS AND SCATTERED THUNDERSTORMS CURRENTLY MOVING
NORTH THROUGH CENTRAL ALABAMA. SEEN AN INCREASE IN COVERAGE OVER THE
LAST HOUR ACROSS SOUTHERN COUNTIES. NOT CERTAIN HOW THIS WILL AFFECT
THE AIRMASS ACROSS THE AREA LATER THIS AFTERNOON...AS THE WARM FRONT
IS STILL TO OUR SOUTH. LOOKING AT THE 16Z SURFACE ANALYSIS...A WARM
FRONT STRETCHES EAST TO WEST ALONG THE ALABAMA/FLORIDA STATE LINE
BEFORE ANGLING TO THE NORTHWEST NEAR EVERGREEN TOWARD MERIDIAN.
DEWPOINTS SOUTH OF THIS LINE ARE IN THE MID TO UPPER 60S AND LOWER
70S. TO THE NORTH...DEWPOINTS IN THE LOWER 60S COOL TO THE MID TO
UPPER 50S SOUTH TO NORTH ACROSS CENTRAL ALABAMA. ON RADAR...A
CONVECTIVE BAND...ARCHING FROM NEAR MERIDIAN SOUTH SOUTHEASTWARD TO
PENSACOLA FL...IS MOVING TO THE NNE. DEWPOINTS FALL INTO THE LOW 60S
BEHIND THIS BAND...AND THERE IS A WIND SHIFT FROM SSE TO SSW BEHIND
THE LINE. THIS APPEARS TO BE OUR EFFECTIVE DRYLINE.

AS THIS CONVECTIVE BAND ROTATES TO THE NNE...IT WILL PUSH THE MOIST
AIR SOUTH OF THE WARM FRONT NORTHWARD INTO SOUTHERN PORTIONS OF
CENTRAL ALABAMA THIS AFTERNOON. THE POTENTIAL FOR SEVERE STORMS WILL
OCCUR IN BETWEEN THE WARM FRONT LIFTING NORTHWARD AND THE CONVECTIVE
BAND MOVING NNE INTO THE AREA. GENERAL TIMING...HAS THE CONVECTIVE
BAND NEAR MONTGOMERY BETWEEN 12-2PM. GIVEN THE UNCERTAINTY OF HOW
QUICKLY THE WARM FRONT LIFTS NORTHWARD...HARD TO DETERMINE HOW
NARROW OR WIDE A CORRIDOR OF INSTABLITY WE WILL BE DEALING WITH
BETWEEN THE TWO FEATURES.

WILL BE WATCHING DEWPOINTS CLOSELY ACROSS THE SOUTHERN EXTENT OF
CENTRAL ALABAMA TO ASSESS ANY CHANGES TO HAZARDS AND THE FORECAST.
NORTH OF THE WARM FRONT...EXPECT WIDESPREAD SHOWERS AND OCCASIONAL
THUNDERSTORMS. HEAVY RAINFALL AND A STRONG WIND GUSTS WILL BE
POSSIBLE.

14

&&

.AVIATION...
18Z TAF DISCUSSION.

WIDESPREAD SHOWERS AND SCATTERED THUNDERSTORMS AFFECTING CENTRAL
ALABAMA TERMINALS THIS AFTERNOON...REDUCING VIS TO LIFR AT TIMES. IN
ADDITION...CIGS ARE IFR TO MVFR. THESE CONDITIONS WILL PERSIST UNTIL
RAIN PUSHES NORTH AND EAST OF THE AREA. TIMED THE BACK EDGE OF THE
RAIN SHIELD COMING ACROSS EAST MS TO APPROXIMATE RAIN ENDING TIMES
AT TERMINALS. HOWEVER...THERE COULD BE LIGHT RAINFALL BEHIND THIS
LINE...BUT CURRENT TRACK AS IT MOVING NORTH OF ALL TERMINALS. THERE
MIGHT BE A PERIOD OF BKN CIGS AS RAIN ENDS...BUT LOW STRATUS WILL
RETURN THIS EVENING. GIVEN THE MOIST GROUND CONDITIONS...EXPECT FOG
TO DEVELOP AS WELL...MIGHT HAVE TO ADJUST VIS DOWN BELOW MVFR.

WINDS WILL CONTINUE TO GUST THIS AFTERNOON...BECOMING SOUTHERLY AT
ALL TERMINALS. THE EXCEPTION IS ANB WHERE EASTERLY WINDS HAVE
PERSISTED TODAY...AND A SHIFT TO THE SOUTHEAST IS EXPECTED.
TONIGHT...WINDS WILL GRADUALLY BECOME SOUTHWESTERLY AT ALL TERMINALS
AROUND 10KTS. AS WINDS INCREASE FROM THE WEST MONDAY MORNING...CIGS
WILL BEGIN TO LIFT. HOWEVER...KEPT MVFR CIGS IN THROUGH AT LEAST
18Z. HAVE INTRODUCED 12-15KT WINDS FOR MONDAY MORNING. SOME GUIDANCE
IS INDICATING HIGHER GUSTS AND THESE VALUES COULD BE INCREASED
WITH FUTURE FORECASTS.

14

&&

.PREV DISCUSSION...
/ISSUED 635 AM CST SUN NOV 23 2014/

HAVE DONE A QUICK UPDATE OF THE GRIDS/TEXT PRODUCTS TO PUSH BACK THE
TIME OF SEVERE POTENTIAL A LITTLE TO 10AM-6PM. THE MORE MOIST
UNSTABLE AIR HAS BEEN SLOW TO COME IN TO CENTRAL ALABAMA THIS
MORNING. THINK THAT THE EASTERLY FLOW HAS AIDED IN THIS NON
TRANSITION AS OF YET. SO HAVE ADJUSTED TS POTENTIAL BY A FEW HOURS.
HAVE ALSO REFRESHED HOURLY TEMPS/DEW POINTS WHILE AT IT. UPDATE
ALREADY OUT.

08/MK

&&

.PREV DISCUSSION...
/ISSUED 456 AM CST SUN NOV 23 2014/

THIS MORNING THE SURFACE RIDGE THAT YESTERDAY STRETCHED ALONG THE
EASTERN SEABOARD HAS NOW MOVED OFF INTO THE ATLANTIC OCEAN. ACROSS
CENTRAL ALABAMA WE STILL HAVE A GENERALLY EAST FLOW. IN THE UPPER
LEVELS...A SHORTWAVE WAS SWINGING ACROSS TEXAS. LATEST SATELLITE
DATA INDICATES THAT THE TROUGH HAS STARTED TO TURN TO THE
NORTHEAST AND SHOULD CONTINUE TO THE NORTHEAST TODAY GIVING A
NEGATIVE TILT TO THE UPPER TROUGH AS IT MOVES ACROSS ARKANSAS AND
THEN INTO KENTUCKY/TENNESSEE BY LATE THIS AFTERNOON. AT THE SAME
TIME...A SURFACE LOW HAS DEVELOPED ACROSS SOUTH TEXAS AND HAS
STARTED TO PUSH NORTHEAST AS WELL IN RESPONSE TO THE SHORTWAVE AND
SHOULD MOVE IT INTO NORTH LOUISIANA THIS MORNING AND INTO
MISSOURI/WESTERN KENTUCKY BY THIS EVENING. THIS SURFACE LOW HAS
ALREADY STARTED TO PULL WARMER/MOIST AIR AND RAIN SHOWERS ACROSS
PORTIONS OF ALABAMA AND INTO GEORGIA WELL AHEAD OF THE DRY LINE
BOUNDARY THAT IS EXPECTED TO PUSH THROUGH DURING THE DAY TODAY.
THEN TONIGHT INTO MONDAY MORNING...A COLD FRONT IS EXPECTED TO
SWEEP THROUGH BEHIND IT TO HELP COOL THINGS OFF FOR THE WEEK.

AS FAR AS PRECIPITATION WITH THIS EVENT...WE WILL CONTINUE TO SEE
ELEVATED SHOWERS AND THEN LATER THIS MORNING THUNDERSTORMS WILL
BEGIN TO SPREAD NORTHWARD ACROSS CENTRAL ALABAMA...BUT THIS
ACTIVITY SHOULD REMAIN ELEVATED FOR THE EARLY MORNING WITH STILL
EXPECTED EASTERLY FLOW AT THE SURFACE. WE SHOULD BEGIN
TRANSITIONING DURING THIS TIME FRAME.

AS WE MOVE INTO THE LATER MORNING HOURS ON SUNDAY...THE LATEST
TRENDS IN MODEL DATA ARE FOCUSING IN OUR BEST OPPORTUNITY FOR
INSTABILITY AND SURFACE BASED CONVECTION AS THE DRY LINE MOVES
ACROSS. ALTHOUGH WE ARE STILL TALKING ABOUT A WINDOW OF 7AM TO
4PM...THE BEST CHANCES LOOK TO BE 11AM THROUGH 4PM...CLOSER TO
THE BOUNDARY PASSAGE...BUT SOME STRONG TO SEVERE ACTIVITY BEFORE
THAT IS NOT TOTALLY OUT OF THE QUESTION IF THE WARM FRONT
PROGRESSES NORTHWARD QUICKER AND WE GET CELLS FIRING UP AHEAD OF
THE LINE. THE QUESTION WILL BE HOW LONG BEFORE OUR DRY LINE
ARRIVAL WILL OUR SURFACE FLOW GIVE WAY TO SOUTHERLY FLOW. THIS MAY
MAKE THE DIFFERENCE IN REALIZING OUR INSTABILITY POTENTIAL AND
EXACTLY HOW FAR NORTH THE HIGHER LOW LEVEL INSTABILITY VALUES
REACH. WITH THE HEAT OF THE DAY POTENTIAL FOR ARRIVAL...WE SHOULD
NOT HAVE AS MUCH OF A PROBLEM GETTING THE REQUIRED INSTABILITY.
AGAIN...THINK HEAVY RAIN WILL BE LESS WIDESPREAD AND MORE LOCALLY
STORM INFLUENCED AS THE LINE SHOULD MOVE AND NOT LINGER.

SOME WRAP AROUND PRECIPITATION IS POSSIBLE AS THE SYSTEM PULLS OUT
OF THE AREA THROUGH MONDAY. ALSO...ANOTHER UPPER SHORTWAVE TROUGH
WILL MOVE ACROSS LATE TUESDAY INTO WEDNESDAY THAT COULD BRING A
FEW SHOWERS ACROSS THE SOUTHEAST. HOWEVER...IT IS EXPECTED TO BE
WELL OUT OF THE AREA BY THURSDAY FOR THANKSGIVING DAY...WITH DRY
WEATHER EXPECTED FOR THE REMAINDER OF THE WEEK INTO NEXT WEEKEND.
A DRY FRONT IS EXPECTED TO MOVE IN ON THANKSGIVING. ALTHOUGH STILL
DRY...THE LATEST MODEL RUN IS SHOWING A WEAKER BOUNDARY THAT MAY
STALL AND FIZZLE OUT. NO MAJOR TEMPERATURES CHANGES ARE EXPECTED
WITH THIS SYSTEM FOR NOW.

08/MK

&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     63  53  61  35  53 / 100  30  20  10  10
ANNISTON    64  54  63  37  54 / 100  30  20  10  10
BIRMINGHAM  66  55  62  38  54 / 100  30  20   0  10
TUSCALOOSA  68  53  62  37  57 / 100  20  10   0   0
CALERA      67  55  63  38  55 / 100  20  10   0  10
AUBURN      66  59  68  41  56 / 100  30  10   0  10
MONTGOMERY  71  58  69  40  58 / 100  20  10   0  10
TROY        72  57  71  40  57 / 100  20  10   0  20

&&

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

&&

$$

08/58










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