Severe Thunderstorm Warning 99, NWS Tallahassee, FL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
450 PM EDT THU MAY 26 2011

...SEVERE THUNDERSTORM WATCH 384 IS IN EFFECT UNTIL 1100 PM EDT FOR
HENRY COUNTY IN SE ALA..AND FOR QUITMAN...CLAY...EARLY...RANDOLPH...
CALHOUN...TERRELL...LEE AND DOUGHERTY COUNTIES IN SRN GA.

...SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH EARLY THIS EVENING
IN SOUTHEAST ALABAMA AND THE WESTERN FLORIDA PANHANDLE...

.SYNOPSIS...
DURING THE MID TO LATE AFTN UPSTREAM RADARS INDICATED MULTIPLE
CLUSTERS OF TSTMS ASSOCIATED WITH NOTED HEIGHT FALLS/FORCING FOR
ASCENT ASSOCIATED WITH A SHORT WAVE MOVING EWD CONTINUED. THIS WAS
ENHANCED BY BOUNDARY LAYER HEATING WHICH SUPPORTED FURTHER
DESTABILIZATION AND A CORRESPONDING INCREASE IN STORM COVERAGE AND
INTENSITY OVER SW AND S/CNTRL ALA. DURING LATE AFTN...PRIMARY
REGIONAL THREAT FOR ISOLATED DAMAGING WINDS AND SEVERE HAIL WILL BE
FROM E-CNTRL AL INTO FAR ERN TN...AND AHEAD OF AN EVOLVING MCS/COLD
POOL ACROSS E-CNTRL/SERN AL.

CLOSER TO HOME...SPC ANALYSIS SHOWED MID LAYER LAPSE RATES AROUND
7.5 C/KM...ALONG WITH HEALTHY SBCAPE VALUES ABOVE 2500 J/KG IN
SOUTHEAST AL AND THE WESTERN FL PANHANDLE. THE 0-6 KM VERTICAL WIND
SHEAR WAS IN THE 30-45 KT RANGE OVER OUR WESTERN ZONES LATE THIS
AFTERNOON AS A PASSING SHORT WAVE ENHANCES THE MID TROPOSPHERIC WIND
FIELD. THE DEEP-LAYER WIND FIELD REMAINED SUFFICIENTLY STRONG TO
POSSIBLY SUPPORT ORGANIZED SUPERCELLS AND LINE SEGMENTS...WITH THE
PRIMARY HAZARDS BEING LARGE HAIL AND DAMAGING WIND GUSTS ALTHO THE
THREAT REMAINS SIGNIFICANTLY LESS THAN FURTHER N/NW. BASED ON THIS
...SPC ISSUED A SEVERE THUNDERSTORM WATCH FOR DOWNSTREAM COUNTIES IN
SE ALA/SRN GA. AS THE MAIN CONVECTION IS PROJECTED TO MOVES E OF THE
LOCAL WATCH AREA AFTER 6PM EDT...IT MAY BE POSSIBLE TO DROP THE
WATCH WELL PRIOR TO 11PM EDT.

AT UPPER LEVELS...
DURING THE LATE AFTN/EVE...VIGOROUS TROUGH/LOW WITH BAND OF MID
LEVEL VORTICITY WAS PROPAGATING EASTWARD OVER THE OHIO VALLEY. A
POTENT SHORT WAVE WAS ROTATING AROUND THE BASE OF THIS TROUGH. THE
MEAN LEVEL (1000-500 MB) RIDGE WAS OFFSHORE PROVIDING A SOUTHERLY
FLOW OVER THE REGION. THIS COMBINATION GENERATED SEVERE WEATHER
ACROSS SE REGION.

DURING FRIDAY...REMNANT OF ERN UPPER TROUGH SPLITTING WITH AN
INCREASINGLY SHEARED NRN PORTION LIFTING NEWD WITHIN STRONGER FLOW
AROUND THE NWRN PERIPHERY OF RIDGING CENTERED OFF THE NORTH ATLANTIC
COAST. WITHIN A WEAKER FLOW REGIME...THE SRN PORTION IS FORECAST TO
TURN SEWD ACROSS THE SOUTH ATLANTIC COAST STATES.

AT LOWER LEVELS...
SURFACE ANALYSIS SHOWED A COLD FRONT FROM WESTERN KY THRU LA THE TX
COAST. REGIONAL RADARS SHOWED THUNDERSTORMS DEVELOPING WELL AHEAD OF
THIS FRONT ACROSS ALA/GA AREA THURS AFTN (SEE ABOVE).

&&

.SHORT TERM...(TONIGHT INTO FRIDAY)
SOUTHERN END OF SHORT WAVE WILL TRACK ACROSS THE REGION WITH
THE STRONGEST DYNAMICS AND COLD FRONT REMAINING NORTH OF OUR AREA.
THE SEVERE THREAT WILL INCREASINGLY DIMINISH THRU THE NIGHT AS
INSTABILITIES DECREASE AND UPPER DYNAMICS (JET MAX) LIFT TO THE
NORTH. THE COLD FRONT IS FORECAST TO ESSENTIALLY STALL AND DISSIPATE
BY THE TIME IT REACHES OUR FORECAST AREA. STILL...THE Q-G FORCING
FROM THE UPPER TROUGH...MESOSCALE BOUNDARIES (LIKE OUTFLOW FROM
THUNDERSTORMS)...AND PLENTY OF MOISTURE AND INSTABILITY WILL ALLOW
ISOLATED TO SCATTERED STORMS TO CONTINUE THROUGH THE NIGHT.

DURING FRIDAY...WITH UPPER DYNAMICS/FRONT STILL CLOSE ENOUGH...
DAYTIME HEATING AND THE WEAK DYNAMICS WILL HELP KICK OFF SCT TSTMS
IN THE MORNING ACROSS MOST OF LOCAL AREA...AND ACROSS MAINLY BIG
BEND AND S/CNTRL GA IN THE AFTN. DUE TO THE STEEP LOW LEVEL LAPSE
AND POSSIBLY HIGH ELEVATED CAPE...A FEW STORMS COULD PRODUCE STRONG
AND GUSTY WINDS AND/OR FREQUENT CLOUD TO GROUND LIGHTNING.

&&

.MARINE...
LOW WINDS AND SEAS WILL CONTINUE INTO THE WEEKEND AS THE PRESSURE
GRADIENT REMAINS WEAK. HOWEVER...WINDS MAY BECOME LOCALLY STRONGER
AND GUSTY NEAR THE COAST EACH AFTERNOON.

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
GA...NONE.
FL...NONE.
GM...NONE.

&&

BLOCK

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE TALLAHASSEE FL
1041 AM EDT THU MAY 26 2011

ALZ065>069-FLZ007>019-026>029-034-108-112-114-115-118-127-128-134-
GAZ120>131-142>148-155>161-GMZ730-750-755-765-770-775-271445-
COFFEE-DALE-HENRY-GENEVA-HOUSTON-INLAND WALTON-CENTRAL WALTON-
HOLMES-WASHINGTON-JACKSON-INLAND BAY-CALHOUN-INLAND GULF-
INLAND FRANKLIN-GADSDEN-LEON-INLAND JEFFERSON-MADISON-LIBERTY-
INLAND WAKULLA-INLAND TAYLOR-LAFAYETTE-INLAND DIXIE-SOUTH WALTON-
COASTAL BAY-COASTAL GULF-COASTAL FRANKLIN-COASTAL JEFFERSON-
COASTAL WAKULLA-COASTAL TAYLOR-COASTAL DIXIE-QUITMAN-CLAY-
RANDOLPH-TERRELL-DOUGHERTY-LEE-WORTH-TURNER-TIFT-BEN HILL-IRWIN-
EARLY-MILLER-BAKER-MITCHELL-COLQUITT-COOK-BERRIEN-SEMINOLE-
DECATUR-GRADY-THOMAS-BROOKS-LOWNDES-LANIER-
APALACHEE BAY OR COASTAL WATERS FROM KEATON BEACH TO OCHLOCKONEE
RIVER FL OUT TO 20 NM-
COASTAL WATERS FROM APALACHICOLA TO DESTIN FL OUT 20 NM-
COASTAL WATERS FROM  OCHLOCKONEE RIVER TO APALACHICOLA FL OUT TO
20 NM-
COASTAL WATERS FROM  SUWANNEE RIVER TO KEATON BEACH OUT 20 NM-
WATERS FROM APALACHICOLA TO DESTIN FL FROM 20 TO 60 NM-
WATERS FROM  SUWANNEE RIVER TO APALACHICOLA FL FROM 20 TO 60 NM-
1041 AM EDT THU MAY 26 2011 /941 AM CDT THU MAY 26 2011/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ALABAMA...
SOUTHWEST AND SOUTH CENTRAL GEORGIA...AND THE FLORIDA BIG BEND
AND PANHANDLE...AND ADJACENT COASTAL WATERS.

.DAY ONE...TODAY AND TONIGHT...

...SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EARLY
EVENING FOR SOUTHEAST ALABAMA AND THE WESTERN FLORIDA PANHANDLE...

SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS AFTERNOON AND
EARLY EVENING...MAINLY IN SOUTHEAST ALABAMA AND WESTERN PORTIONS
OF THE FLORIDA PANHANDLE. THE AIRMASS IS FORECAST TO BECOME VERY
UNSTABLE THIS AFTERNOON AS DAYTIME HEATING COMBINES WITH COOLING
ALOFT. AN APPROACHING UPPER LEVEL DISTURBANCE AND OUTFLOW FROM
UPSTREAM THUNDERSTORMS MAY TRIGGER THUNDERSTORM DEVELOPMENT. ALTHOUGH
THE WINDS ALOFT MAY NOT BE AS STRONG AS THEY NORMALLY ARE IN
WINTERTIME SEVERE WEATHER OUTBREAKS...THEY MAY BE JUST STRONG ENOUGH
TO COMBINE WITH THE IMPRESSIVE INSTABILITY TO PRODUCE ISOLATED
SEVERE THUNDERSTORMS. THE MAIN THREAT WILL BE LARGE HAIL AND
MARGINALLY SEVERE WIND GUSTS OF AROUND 60 MPH. THE SEVERE WEATHER
THREAT WILL END AFTER SUNSET. ELSEWHERE...ISOLATED THUNDERSTORMS
ARE POSSIBLE...BUT ORGANIZED SEVERE WEATHER IS UNLIKELY.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS REQUESTED IN SOUTHEAST ALABAMA AND WESTERN
FLORIDA PANHANDLE IF ANY WATCHES OR WARNING ARE ISSUED.

FOR ADDITIONAL INFORMATION...VISIT THE NATIONAL WEATHER SERVICE
WEBSITE ON THE INTERNET AT WEATHER.GOV...THEN CLICK ON YOUR AREA
OF INTEREST ON THE NATIONAL MAP.

FOURNIER