Wind Advisory 22, NWS Birmingham, AL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
417 AM CDT WED MAY 25 2011

.DISCUSSION...

A STRONG VERTICALLY STACKED STORM SYSTEM WILL MAKE ITS WAY EAST
TODAY AND COVER MOST OF THE MISSISSIPPI VALLEY REGIONS ADDING YET
ANOTHER CHAPTER TO THIS SPRING SEVERE WEATHER SEASON. MOST OF THE
ACTION WILL BE JUST UPSTREAM FROM ALABAMA TODAY AND WILL GET
RATHER ACTIVE ACROSS MISSISSIPPI AND WESTERN TENNESSEE LATER
TODAY. WE WILL WATCH ANXIOUSLY AS THE LINE OF CONVECTION AND
SUPERCELL DEVELOPMENT TAKES PLACE AS IT WILL LIKELY SLOWLY SHIFT
EASTWARD TOWARDS THE STATE LINE LATER THIS EVENING. DEPENDING ON
ITS EXACT EVOLUTION...COULD MAKE OR BREAK OUR SEVERE WEATHER
PROBABILITIES LATER TONIGHT. ONE TREND THAT IS ON THE IMMEDIATE
HORIZON IS THE SPEED AT WHICH IT TRANSLATES EAST. MODELS HAVE BEEN
TRENDING SOMEWHAT FASTER WITH TIME...SO WE WILL NEED TO BE READY
BY MIDNIGHT...OR PERHAPS A BIT EARLIER. AS THE STORMS DEVELOP ON
THE LEE SIDE OF THE TROUGH AND JET AXIS...THE GENERAL STORM MOTION
WILL BE NORTHEAST....WITH A SLOWER TRANSLATION EASTWARD AS THE
SYSTEM TURNS NORTHEAST TOWARDS THE NORTHERN TENNESSEE AND OHIO
VALLEYS. THE JET STRUCTURE CONTINUES TO BE DECENTLY IMPRESSIVE FROM
AROUND 06 TO 15Z MAINLY ACROSS OUR NORTHWESTERN CWA...AND THIS
SEEMS TO BE CONSISTENT WITH OUR TARGET OF OPPORTUNITY FOR THE MOST
INTENSE WEATHER OVERNIGHT. TAKING A CLOSER LOOK AT THE 0 TO 6KM
BULK SHEAR VECTORS OR MY GO-TO PRODUCT FOR MODE OF CONVECTION...IT
APPEARS THAT THE SYSTEM WILL TAKE ON A MORE LINEAR LOOK THE
FURTHER IT PROGRESSES EASTWARD. ADD TO THAT THE PROBABILITY OF
BEING COLD POOL DOMINATED BY THE TIME THE CELLS REACH THE STATE
LINE...AND WE ARE LIKELY GOING TO SEE A BROKEN SQUALL...MCS...OR
EVEN A QLCS BY THE TIME IT ENTERS OUR CWA. THERE IS ALSO THE
POTENTIAL FOR SOME BOWING LINE SEGMENTS AS WELL. TOOK A LONG HARD
LOOK AT THE PROBABILITY FOR SUPERCELLS...AND IT DOES LOOK LIKE IT
WOULD BE A DIFFICULT ENVIRONMENT FOR
SUSTAINABILITY...HOWEVER...THERE IS A NARROW WINDOW WHERE THE
VECTORS COULD BE ORIENTED IN SUCH A FASHION THAT ONE OR TWO ARE
CAN NOT BE TOTALLY RULED OUT...AS LONG AS THE COLD POOLS ARE NOT
OVERLY DOMINANT.

WHILE THE SHEAR VECTORS LOOK DECENT...I DO CONTINUE TO STRUGGLE
WITH INSTABILITY. AT THIS POINT...AM JUST NOT CONFIDENT THAT
MODELS HAVE A GOOD HANDLE ON THE LOWER BOUNDARY LAYER. MODEL
SOUNDINGS ARE STILL INDICATING THAT SOME DECOUPLING AND SURFACE
COOLING WILL OCCUR BETWEEN SUNSET AND MIDNIGHT....HOWEVER...THE
SURFACE WIND SPEEDS MAY VERY WELL KEEP THE BL WELL MIXED THROUGH
THE EVENING HOURS...KEEPING THE INSTABILITY HIGHER THAN FORECAST.
IF THERE IS SOMETHING TO WATCH IN THE MESOSCALE...THAT WOULD
CERTAINLY BE A FACTOR THAT NEEDS TO BE MONITORED CLOSELY.
OTHERWISE...THERE SHOULD BE SOME MEAGER DESTABILIZATION AS THE
PREFRONTAL BOUNDARY APPROACHES...ON THE ORDER OF 1000 TO 1500
J/KG. WITH THESE ELEMENTS IN PLACE...WOULD STILL CONTEND THAT
DAMAGING STRAIGHT-LINE WINDS AND SOME HAIL WOULD CONTINUE TO BE
THE MAIN THREATS...HOWEVER...WITH THE DECENT TURNING HODOGRAPHS AN
ISOLATED TORNADO WILL STILL BE PROBABLE THROUGH THE OVERNIGHT AND
TOMORROW MORNING.

AS WE MOVE INTO THE LATE MORNING AND AFTERNOON HOURS...OR AS THE
ACTUAL FRONTAL BOUNDARY APPROACHES...THE GOOD JET DYNAMICS WEAKEN
CONSIDERABLY AS THEY MOVE OFF TO THE NORTH. WE ARE STILL EXPECTING
SOME DECENT RE-DEVELOPMENT WITH DAYTIME HEATING AS THE FRONT
SLOWLY PASSES FROM WEST TO EAST. HOWEVER...THE VEERING PROFILES IN
THE LOWEST 3 KM WILL LESSEN THE TORNADO THREAT...HOWEVER...STRONG
DAMAGING WINDS AND SOME HAIL WILL STILL BE POSSIBLE MAINLY UNTIL
SUNSET TOMORROW EVENING. THE FRONT IS STILL EXPECTED TO SLOW QUITE
A BIT TOMORROW AFTERNOON...LEAVING MOST OF THE CWA IN THE THREAT
WINDOW UNTIL WE LOSE DAYTIME HEATING...THEN SHOWERS AND THUNDERSTORMS
WILL LIKELY CONTINUE THROUGH AT LEAST PORTIONS OF THE EVENING AND
OVERNIGHT BEFORE EXITING EAST EARLY FRIDAY.

IN THE LONGER TERM...OVER THE WEEKEND AND NEXT WEEK...SIGNIFICANT
DEEP LAYER RIDGING WILL ONCE AGAIN BUILD OVER THE SOUTHEAST. IT
MAY NOT BE QUITE AS HOT AS INITIALLY ADVERTISED AS EASTERLY FLOW
IS EXPECTED AND WILL POSSIBLY KEEP US AROUND 90 VERSUS TO MID 90S.
THE WEATHER LOOKS TO TURN MOSTLY DRY FOR THE EXTENDED AS WELL.

17/KLAWS

&&

.AVIATION...06Z TAF DISCUSSION.

STILL EXPECTING A STRATUS DECK TO BUILD INTO THE AREA OVERNIGHT
FROM THE SOUTH. OTHERWISE...LOTS OF CIRRUS FROM SOUTHERN PLAINS
CONVECTION. CLOUDS WILL SLOWLY MIX OUT WED MORNING WITH WINDS
INCREASING OUT OF THE SOUTH. WINDS ARE EXPECTED TO BE GUSTY AT
TIMES WITH POTENTIAL FOR 25KTS.

NOTICE...KEET TAF WILL HAVE (AMD LTD TO VIS WIND AND WX) AMENDED
TO THE END OF THE FORECAST UNTIL FURTHER NOTICE. THE CEILOMETER
DATA WILL BE GOING THROUGH NUMEROUS TESTS AND MONITORED FOR
ACCURACY

&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     90  68  82  61  83 /  10  20  70  60  10
ANNISTON    92  68  84  65  85 /  10  10  50  60  20
BIRMINGHAM  90  73  83  65  83 /  10  20  60  40  10
TUSCALOOSA  93  72  86  64  86 /  10  30  60  30  10
CALERA      91  71  84  65  84 /  10  20  50  40  10
AUBURN      91  68  85  69  85 /   0  10  20  40  20
MONTGOMERY  91  70  87  69  88 /  10  10  20  40  10
TROY        91  67  87  69  87 /   0  10  20  20  20

&&

.BMX WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FROM NOON TODAY TO 7 PM CDT THIS EVENING FOR THE
FOLLOWING COUNTIES: AUTAUGA...BIBB...BLOUNT...CHILTON...DALLAS...
FAYETTE...GREENE...HALE...JEFFERSON...LAMAR...LOWNDES...
MARENGO...MARION...PERRY...PICKENS...SHELBY...SUMTER...
TUSCALOOSA...WALKER...WINSTON.

&&

17/88

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BIRMINGHAM AL
730 PM CDT TUE MAY 24 2011

ALZ011>015-017>050-260030-
AUTAUGA-BARBOUR-BIBB-BLOUNT-BULLOCK-CALHOUN-CHAMBERS-CHEROKEE-
CHILTON-CLAY-CLEBURNE-COOSA-DALLAS-ELMORE-ETOWAH-FAYETTE-GREENE-HALE-
JEFFERSON-LAMAR-LEE-LOWNDES-MACON-MARENGO-MARION-MONTGOMERY-PERRY-
PICKENS-PIKE-RANDOLPH-RUSSELL-SHELBY-ST CLAIR-SUMTER-TALLADEGA-
TALLAPOOSA-TUSCALOOSA-WALKER-WINSTON-
730 PM CDT TUE MAY 24 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE COUNTIES SERVED BY THE
NATIONAL WEATHER SERVICE OFFICE IN BIRMINGHAM.

.DAY ONE...TONIGHT.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

SEVERE STORMS ARE POSSIBLE ACROSS ALL OF CENTRAL ALABAMA ON THURSDAY
AHEAD OF AN APPROACHING COLD FRONT. TWO WAVES OF SEVERE WEATHER ARE
EXPECTED...AND EXACT TIMING WILL DEPEND HEAVILY ON DEVELOPMENT TO
OUR WEST AND ON THE SPEED AND EVOLUTION OF THE COLD FRONT. THE FIRST
OF THESE TWO WAVES IS EXPECTED BETWEEN 4AM AND 12PM. THE MAIN
HAZARDOUS THREATS FOR THURSDAY MORNING INCLUDE DAMAGING STRAIGHT
LINE WINDS...LARGE HAIL...AND CLOUD TO GROUND LIGHTNING. CONFIDENCE
IN THE TORNADO THREAT REMAINS LOW...HOWEVER THERE IS A SMALL CHANCE
OF AN ISOLATED TORNADO GENERALLY ALONG AND NORTH OF INTERSTATE 20
AND WEST OF INTERSTATE 65.

THE SECOND WAVE OF SEVERE STORMS IS EXPECTED BETWEEN 12PM AND 8PM.
STORMS MAY GENERALLY WEAKEN THROUGHOUT THE DAY...BUT THE CHANCE OF
DAMAGING STRAIGHT LINE WINDS...LARGE HAIL...AND CLOUD TO GROUND
LIGHTNING REMAINS POSSIBLE. ALTHOUGH...THE TORNADO THREAT DURING THE
AFTERNOON IS LOWER...IT CAN NOT BE COMPLETELY RULED OUT.

.SPOTTER INFORMATION STATEMENT...

ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT MAY BE NEEDED
ON THURSDAY.