Severe Thunderstorm Warning 173, NWS Tallahassee, FL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
235 PM EDT FRI AUG 25 2000

HAVE UPDATED ZONES TO REFLECT WATCH BOX #707.

CURRENTLY RADARS ARE DETECTING SCATTERED CONVECTION OVER MAINLY
EASTERN SECTION OF MY FORECAST AREA AND MOVING SE AT ABOUT 25 MPH.
AS DRIER AIR CONTINUES TO FILTER INTO MY FORECAST AREA I WOULD
EXPECT TO SEE SCATTERED SHOWERS DEVELOP ALONG THE INTERFACE BETWEEN
THE DRY AND MOIST AIR...SPECIFICALLY THIS WOULD BE OVER EXTREME SE
ALABAMA AND THE FLORIDA PANHANDLE AND PUSHING INTO THE BIG BEND AS
WELL AS THE COASTAL WATERS. WILL TAILOR THE 'TONIGHT' PERIOD OF MY
ZONES BASED ON RADAR TRENDS...BUT AT THIS TIME I THINK 20 PERCENT OR
SO SHOULD SUFFICE.

MODELS FAIRLY SIMILAR IN THE UPPER LEVELS WITH CURRENT TROF SEEN IN
WATER VAPOR IMAGERY OVER THE SOUTHEASTERN U.S. CONTINUING TO SLIDE
EASTWARD INTO THE ATLANTIC WATERS BY EARLY SATURDAY. ANOTHER
SHORTWAVE APPROACHES THE FORECAST AREA RIDING OVER THE TOP OF THE
RIDGE ON SUNDAY. HOWEVER...THERE ARE SOME DIFFERENCES IN THE STRENGTH
AND POSITION OF THIS NEXT SHORTWAVE. ETA HAS THE HIGHEST OMEGA AND
MOISTURE ASSOCIATED WITH THE SYSTEM OVER EASTERN TN BY 12Z SUN...
WHILE NGM SHOWS A BULLSEYE OF OMEGA THAT EXTENDS FROM EASTERN TN
INTO SOUTHEAST ALABAMA...AND FINALLY AVN INDICATES THESE FEATURES
OVER CENTRAL KENTUCKY. AFTER THAT TIME MODELS CAN'T AGREE AND ETA
SHOWS BEST LIFT AND MOISTURE RIGHT OVER THE MIDDLE OF MY CWA...AND
AVN HAS IT PULLING OFF TO THE E OR NE INTO THE MID ATLANTIC REGION
BY LATE SUNDAY (00Z MONDAY).

MODELS ALSO INDICATE IN FORECAST SOUNDINGS THAT PW'S WILL DROP TO
AROUND 1.5 INCHES BY SATURDAY...BUT THEN AS THE NEXT SHORTWAVE
APPROACHES PW'S INCREASE TO AROUND THE 2 INCH MARK BY LATE IN THE
FORECAST PERIOD.

SEABREEZE REGIME TYPE FOR SATURDAY IS A TYPE 8...1000-700MB MEAN
VECTOR WIND OF NW < 10 KNOTS OVER THE PANHANDLE ZONES AND A TYPE
4...W-SW FLOW < 10 KNOTS OVER THE BIG BEND ZONES. CLIMO WOULD
SUGGEST POPS OF 30-40 PERCENT FOR THE PANHANDLE ZONES AND 40-50 FOR
THE BIG BEND. HOWEVER..SINCE PW'S ARE WELL BELOW CLIMO VALUES WILL
UNDERCUT THESE NUMBERS SIGNIFICANTLY AND USE 10 TO 20 PERCENT FOR
SATURDAY. WITH THE APPROACH OF THE NEXT SHORTWAVE ON SUNDAY...THE
SEABREEZE REGIME FOR THEN IS A W-NW FLOW < 10 AND THIS WARRANTS POPS
IN THE 40-50 PERCENT RANGE OVER THE FLORIDA ZONES AND 30-40 OVER SE
AL AND SW GA. DUE TO THE UNCERTAINTY OF THE SHORTWAVE ON SUNDAY WILL
USE 40 PERCENT ACROSS THE BOARD.

GUIDANCE TEMPS LOOK VERY SIMILAR AND WILL GENERALLY FOLLOW.

MARINE: GENERALLY A SOUTHERLY COMPONENT TO THE COASTAL FORECAST THRU
SATURDAY NIGHT...BUT LIGHT (10 KNOTS OR LESS).

FIRE WEATHER: THINK RH'S ON SATURDAY WILL REMAIN ABOVE RED FLAG
CRITERIA...SO NO WATCHES OR WARNINGS ANTICIPATED.

EXTENDED: LOOKS LIKE A SHIFT IN THE PATTERN (AT LEAST AS SEEN IN THE
MFR) WITH A RIDGE IN THE EAST AND TROF IN THE WEST. SEABREEZE CLIMO
SUGGEST CHANCE POPS EACH DAY.

PRELIMINARY NUMBERS (SUBJECT TO CHANGE):

TLH  069/096 070/095  3214
PFN  076/092 076/091  2214
DHN  071/097 072/095  -1-4
ABY  070/097 071/095  -1-4
VLD  071/096 070/095  3114

.TLH...

AL...NONE.
GA...SVR TSTM WATCH #707 INCLUDES PORTIONS OF SW GA UNTIL 00Z.
FL...SVR TSTM WATCH #707 INCLUDES MUCH OF THE FL BIG BEND UNTIL 00Z.

MOLLERE