Severe Thunderstorm Warning 68, NWS Tallahassee, FL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
215 PM EDT THU JUN 22 2000

IN THE UPPER LEVELS MODELS ZIP UPPER LEVEL TROF OVER THE GREAT LAKES
REGION EASTWARD WITH WEAK SHORTWAVE AND ASSOCIATED VORT LOBE/AXIS
OVER THE LOWER MISSISSIPPI RIVER VALLEY NUDGING TO THE SOUTHEAST
INTO MY FORECAST AREA OVERNIGHT. ETA/AVN ARE SIMILAR IN MAINTAINING
SOME STRENGTH TO THIS FEATURE...WHILE NGM WEAKENS THE VORT SIGNATURE
CONSIDERABLY.

AT THE SURFACE THE BOUNDARY TO OUR NORTH CONTINUES TO PUSH SOUTH
WITH THE ETA BEING THE SLOWEST OF THE THREE MODELS. NGM/AVN HAVE THE
BOUNDARY ORIENTED FROM AROUND APALACHICOLA THEN NE TO VALDOSTA GA
AND COASTAL SOUTH CAROLINA BY 12Z FRI. AFTER THIS TIME MODELS
INDICATE THAT BOUNDARY STALLS ACROSS THE REGION. MODEL TIME HEIGHT
SECTIONS...FORECAST SOUNDINGS AND 1000-500MB MEAN RH VALUES ALL SHOW
MOISTURE DECREASING FROM THE NW AS THE FRONT SLIDES TO THE SE. ALL
MODEL SOUNDINGS SHOW PWAT VALUES AROUND 1.9 INCHES THEN DECREASING
THRU THE FORECAST PERIOD...BUT NORTHERN AREAS OF MY FORECAST AREA
SHOW THE MOST DRAMATIC DECREASE.

HAVE GENERALLY FOLLOWED FWC POP GUIDANCE...BUT HAVE TWEAKED IT SOME
TO ACCOUNT FOR SEABREEZE INFLUENCES FOR FRIDAY AND SATURDAY.
FRIDAYS SEABREEZE REGIME LOOKS LIKE A TYPE 4 (LIGHT W FLOW) FOR THE
EASTERN BIG BEND...WHICH CLIMATOLOGICALLY RESULTS IN RATHER HIGH
POPS (60 PERCENT). ON THE OTHER HAND THE PANHANDLE WILL BE IN A TYPE
8 REGIME (LIGHT NW FLOW) WHICH CORRESPONDS TO ABOUT 40 PERCENT POPS
CLIMATOLOGICALLY. HOWEVER...WITH THE ANTICIPATED DRYING HAVE
UNDERCUT THESE VALUES SLIGHTLY.

FOR FRIDAY...WILL GO WITH 20 PERCENT POPS OVER MOST OF THE NORTHERN
ZONES...THEN 30-40% OVER THE PANHANDLE AND WESTERN BIG BEND...BUT
WILL KEEP 50% OVER THE EXTREME EASTERN BIG BEND WHERE STALLING FRONT
AND MOST FAVORABLE SEABREEZE INFLUENCE WILL KEEP RISK OF STORMS
HIGHER.

FOR SATURDAY...GENERALLY 20 PERCENT POPS NORTHERN ZONES...30% FL AND
S GA...AND 40% EXTREME EASTERN BIG BEND. SEABREEZE REGIME BY THEN
SHOULD BE LIGHT EAST (TYPE 2) WHICH FAVORS LOW POPS. HOWEVER...EAST
FLOW SHOULD ALLOW ECSB TO PUSH FARTHER WEST AND MY EASTERN ZONES
WILL HAVE A LITTLE BETTER CHANCE AT SEEING CONVECTION DEVELOP.

TEMP GUIDANCE IS VERY SIMILAR...BUT WILL GO A LITTLE WARMER FOR
NORTHERN ZONES...ESPECIALLY ON SATURDAY WHERE THE INFLUENCE OF THE
SURFACE HIGH AND DRYING AIRMASS WILL ALLOW TEMPS TO CLIMB A LITTLE
HIGHER. LOWS LOOK REASONABLE.

MARINE: GENERALLY LOOKS LIKE LIGHT W TO SW FLOW THROGH THE PERIOD
AND SEAS 2 FEET OR LESS.

FIRE: NO REQUIREMENTS.

EXTENDED: WITH SOUTH TO SOUHTWEST FLOW AND ANOTHER APPROACHING
SYSTEM FROM THE NORTHWEST...WILL CONTINUE THE CHANCE OF POPS IN THE
EXTENDED FORECAST.

PRELIM NUMBERS...

TLH  073/093 072/093 3423
PFN  077/090 075/090 3313
DHN  074/094 072/095 3212
ABY  073/095 071/095 3212
VLD  073/093 072/093 3423

.TLH...
AL...NONE.
GA...NONE.
FL...NONE.

MOLLERE