Area Forecast Discussion
Issued by NWS Birmingham, AL

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS64 KBMX 220558
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
1158 PM CST FRI NOV 21 2014

.UPDATE...
FOR 06Z AVIATION.

&&

.DISCUSSION...

NO MAJOR CHANGES THIS EVENING REGARDING THE FORECAST. ADJUSTED THE
HOURLY TRENDS BUT ALL ELSE REMAINS ON TRACK. THE LATEST MODEL RUNS
CONTINUE THE SAME GENERAL SCENARIO OUTLINED IN THE AFTERNOON
DISCUSSION. MORE TO COME OVERNIGHT IN NEXT DISCUSSION.

75


&&

.AVIATION...
06Z TAF DISCUSSION.

KEPT VFR CONDITIONS ACROSS CENTRAL ALABAMA A BIT LONGER THAN THE
PREVIOUS PACKAGE. MOISTURE REALLY INCREASES THROUGH THE MORNING
HOURS ON SATURDAY FROM THE SOUTHEAST. BACKED UP MVFR CEILINGS AT
MGM/TOI TIL AROUND 15Z AND HELD THEM THERE THE REMAINDER OF THE
FORECAST PERIOD. MOISTURE WILL ALSO INCREASE FROM THE SOUTHWEST
AND HAVE VFR CEILINGS MOVING INTO THE SOUTHERN SITES A FEW HOURS
BEFORE RESTRICTIONS AND NORTHERN SITES BY 16-18Z. THEN TOOK THE
NORTHERN SITES DOWN TO MVFR 20-22Z. AS THE EVENING PROGRESSES SOME
LIGHT RAIN WILL BEGIN AT THE SOUTHERN SITES AND SPREADS AREA WIDE
JUST BEYOND THE FORECAST PERIOD AS A DYNAMIC SYSTEM APPROACHES.

THE BIGGEST CHALLENGE WILL BE HOW LOW CEILINGS DEVELOP SOUTH.

75

&&

.PREV DISCUSSION...
/ISSUED 326 PM CST FRI NOV 21 2014/

UPPER LEVEL SHORTWAVE TROUGH NOW OVER SOUTHERN CALIFORNIA WILL
PROGRESS EASTWARD OVER THE NEXT 2 DAYS...EVENTUALLY BECOMING
NEGATIVELY TILTED AS IT MOVES ACROSS THE LOWER MS RIVER VALLEY.
BROAD AREA OF LIFT ASSOCIATED WITH THIS SYSTEM WILL HELP BRING
WIDESPREAD RAIN AND A CHANCE OF THUNDERSTORMS TO CENTRAL ALABAMA
FOR THE LATTER HALF OF THE WEEKEND.

LATEST COMPUTER MODEL RUNS CONTINUE TO INDICATE THAT WARM FRONTAL
TYPE RAIN WILL SPREAD NORTHWARD FROM THE NORTHERN GULF INTO
CENTRAL ALABAMA STARING AROUND (OR JUST BEFORE) MIDNIGHT SATURDAY
NIGHT. INTERESTINGLY...SOME OF THE MODELS ARE NOW SHOWING THAT THE
DEEPEST MOISTURE AND AREA OF HEAVIEST RAIN MAY ACTUALLY GO MORE
INTO GA THAN AL. IF THAT ENDS UP VERIFYING...THEN THERE IS A
SLIGHTLY BETTER CHANCE THAT THE COASTAL WARM FRONT COULD MOVE
FARTHER NORTH THAN PREVIOUSLY THOUGHT (AND NOT BE LOCKED IN PLACE
BY THE LARGE RAIN MASS). THE IMPLICATION OF THIS SCENARIO WOULD BE
THAT ANY SEVERE WEATHER THREAT THAT MATERIALIZES WOULD ALSO BE
ABLE TO ADVANCE FARTHER NORTH.

ANOTHER POTENTIAL DEVELOPMENT TO BE WARY OF IS A MORE DELAYED
ARRIVAL OF THE INITIAL WIND SHIFT AND DRY LINE FROM THE WEST AFTER
SUNRISE SUNDAY. AGAIN...DELAYED ARRIVAL IMPLIES MORE TIME TO
POTENTIALLY WARM UP AND BECOME UNSTABLE. THE CURRENT CONSENSUS
FROM THE FORECASTERS HERE IS THAT THE WARM FRONT WILL NOT GET MUCH
FARTHER NORTH THAN (ROUGHLY) A DEMOPOLIS-AUBURN LINE...AND THAT
FORCING ASSOCIATED WITH THE DRY LINE WILL QUICKLY MOVE THROUGH
DURING THE 6 AM TO 3 PM TIME FRAME. THIS KEEPS ANY SEVERE WEATHER
POSSIBILITIES PRIMARILY IN OUR SOUTHERN HALF.

AFTER THE PRIMARY COLD FRONT GOES THROUGH SUNDAY NIGHT OR
MONDAY...MOS GUIDANCE IS INSISTING ON KEEPING 20-30 PERCENT POPS
FOR OUR AREA THROUGH THE MIDDLE OF THE WEEK. I SUPPOSE THIS IS IN
RESPONSE TO SEVERAL MORE SHORTWAVES ROUNDING THE BASE OF THE
LARGER SCALE EASTERN STATES TROUGH...AND THE POSSIBILITY THAT
LIGHT SHOWERS...SPRINKLES...OR DRIZZLE COULD SQUEEZE OUT A COUPLE
HUNDREDTHS OF AN INCH OF RAIN. I`VE CHOSEN TO GO WITH A RAIN FREE
FORECAST FOR NOW...WITH POPS LESS THAN 20 PERCENT. ONCE WE GET
FINISHED WITH THE INITIAL LARGE SCALE RAIN EVENT WE CAN LOOK AT
THE FOLLOWING POPS MORE CLOSELY.

/61/

&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     36  60  47  65  55 /   0   0  60 100  30
ANNISTON    38  60  49  68  56 /   0   0  70 100  30
BIRMINGHAM  42  63  52  69  56 /   0  10  60  90  20
TUSCALOOSA  42  64  55  71  55 /  10  10  70  90  20
CALERA      42  63  52  70  56 /   0  10  70  90  20
AUBURN      42  61  51  70  59 /   0  10  80 100  20
MONTGOMERY  40  66  54  74  59 /   0  10  80  90  10
TROY        42  64  55  74  60 /   0  10  80  90  20

&&

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

&&

$$







USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.