Severe Thunderstorm Warning 193, NWS Jacksonville, FL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSONVILLE FL
235 PM EDT THU JUL 2 2009

.SYNOPSIS...PERSISTENT LARGE SCALE UPPER TROF EXTENDS FROM THE
CENTRAL GREAT LAKES REGION TO THE GULF COAST. H2O VAPOR IMAGERY
SHOWS PLENTY OF DRY AIR OVER THE N 1/2 OF OUR COUNTY WARNING AREA
WITH A WEAK SHORTWAVE CUTTING ACROSS CENTRAL GA AND S AL. A SLOW
MOVING COLD FRONT EXTENDS FROM THE E CAROLINAS ACROSS S CENTRAL GA
AND INTO S AL. FORCING FROM THE SFC FRONT AND THE MID-LEVEL
SHORTWAVE IS PRODUCING A DEVELOPING LINE OF CONVECTION WITH
LIGHTNING DETECTED N OF KABY. WEAK SUBSIDENCE NOTED AT 500MB ON
THE KJAX AND KTAE 12Z SOUNDINGS. WITH MODEST SW SFC FLOW...TEMPS
RANGE FROM NEAR 90 OVER THE S ZONES TO THE MID 90S ACROSS THE N.

.SHORT TERM...BEST MOISTURE CONTINUES TO BE OVER THE S ZONES.
HOWEVER...LOW AND MID-LEVEL FORCING ENCROACHING FROM THE NW SHOULD
CONTINUE TO PRODUCE ISOLD CONVECTION AS IT MOVES INTO OUR NW ZONES
LATE THIS AFTN AND THIS EVENING. AS THIS FORCING BEGINS TO
INTERACT WITH SLIGHTLY MORE MOISTURE...LOW END CHANCE TSTMS MAY
DEVELOP ACROSS SE GA AND EXTREME NE FL DURING THE EARLY EVENING.
TIMING WILL BE A HUGE FACTOR AS DAYTIME HEATING WILL BE WANING BY
THEN.

BETTER CHANCES OF POPS OVER NE FL AND EXTREME SE GA ON FRI AS
STRONGER SHORTWAVE PROGGED TO ENTER THE AREA FROM THE NW DURING
MAX DAYTIME HEATING. HAVE STILL CAPPED THE POPS AT AROUND 30
PERCENT DUE TO CONTINUED DRY AIR ALOFT. EVEN DRIER AIR PROGGED BY
BOTH THE NAM AND GFS ON INDEPENDENCE DAY. HAVE REDUCED POPS TO
SLIGHT CHANCE OVER COASTAL SE GA AND MUCH OF NE FL WITH LOW END
CHANCE OVER OUR SE ZONES.

TEMPERATURES WILL REMAIN WARM THRU PERIOD WITH DAYTIME HIGHS
SOLIDLY IN THE MID 90S ACROSS MOST OF THE AREA AND A FEW LOCALES
IN THE UPPER 90S. SW FLOW LEAD TO A LATE ATLC SEABREEZE AND LITTLE
RELIEF FROM HEAT UNTIL LATE IN THE DAY.

.LONG TERM...FRONT N OF THE AREA AND A SERIES OF DISTURBANCES WILL
LEAD TO BETTER CHANCES OF PRECIP AREA-WIDE DURING MOST OF THE
EXTENDED PERIOD. THIS...AND LOWER OVERALL THICKNESSES...WILL LEAD
TO MAX TEMPS CLOSER TO CLIMO.

&&

.AVIATION...VFR CONTINUES WITH VCTS FOR NOW BY 21Z-22Z. HAVE ELECTED
TO INSERT TEMPO GROUPS FOR GNV...JAX...SSI AND VQQ FOR TSRA BASED ON
MODEL GUIDANCE AND RADAR IMAGERY. VIS IMAGERY EARLIER TODAY SHOWED
INCREASED CU FIELD OVER SRN GA WHICH SEEMS TO BE SUPPORTED OF
MESOSCALE MODEL GUIDANCE SHOWING SCT TSRA DEVELOPING AND SHIFTING
ESE LATE THIS AFTERNOON. HAVE ENDED TSRA BY ABOUT 02Z. INSERTED MVFR
BR FOR VQQ FOR NOW BUT ANTICIPATE PREVAILING VFR INTO FRI.

&&

.MARINE...ANTICIPATE ANOTHER NOCTURNAL WIND INCREASE OVER OFFSHORE
WATERS AND WILL HEADLINE A SCEC. TROUGH OF LOW PRESSURE SINKS SWD
NEXT 48 HRS WHICH WILL DECREASE OVERALL PRES GRADIENT SO NIGHTLY
SURGE FRI NIGHT MAY NOT A SUPPORT ANOTHER REPEAT OF TONIGHT.
HOWEVER...TROUGH AXIS LIFTS NWD/BECOMES DIFFUSE BY SUN WHICH WILL
SETUP PREVAILING AND INCREASING SWLY FLOW AGAIN WITH SCEC HEADLINES
POSSIBLE AGAIN...MAINLY AT NIGHT AND IN THE OFFSHORE WATERS.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  71  96  68  97 /  20  20  10  10
SSI  77  94  76  91 /  30  20  20  20
JAX  75  96  72  96 /  30  30  30  20
SGJ  75  92  75  91 /  20  30  30  20
GNV  73  95  73  95 /  20  30  20  20
OCF  74  94  73  94 /  20  30  20  20

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GA...NONE.
AM...NONE.

&&

CARROLL/SHASHY/MCALLISTER