DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 211619
SWODY1
SPC AC 211617

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1117 AM CDT SAT APR 21 2012

VALID 211630Z - 221200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT FOR
THE FL PENINSULA...

...FL PENINSULA THIS AFTERNOON THROUGH TONIGHT...
A MIDLEVEL LOW S OF LA WILL MOVE EWD TO THE FL PENINSULA BY LATE
TONIGHT. IN ADVANCE OF THE MIDLEVEL WAVE...A SURFACE LOW ACROSS THE
N CENTRAL GULF OF MEXICO WILL DEVELOP ENEWD TO THE NE GULF LATE
TODAY AND ACROSS N FL TONIGHT. A BAND OF THUNDERSTORMS ACROSS THE
ERN GULF OF MEXICO PRECEDES A WEAK LEAD SHORTWAVE TROUGH...AND THIS
CONVECTION WILL APPROACH THE FL BIG BEND AND W COAST BY EARLY-MID
AFTERNOON. THE FUTURE OF THIS CONVECTION IS A BIT UNCERTAIN BASED
ON MESOSCALE FACTORS. OUTFLOW ASSOCIATED WITH ONGOING CONVECTION
JUST S OF THE KEYS IS INTERFERING WITH THE NEWD RETURN OF THE
RICHEST BOUNDARY LAYER MOISTURE FROM THE YUCATAN CHANNEL.
ADDITIONALLY...HIGH CLOUD DEBRIS IS SLOWING SURFACE HEATING ACROSS
CENTRAL/S FL.

AFTERNOON MLCAPE OF 1000-1500 J/KG IS EXPECTED ACROSS THE
PENINSULA...WITH STRONGER SURFACE HEATING ACROSS N FL...AND RICHER
BOUNDARY LAYER MOISTURE FARTHER S. MEANWHILE...THE PRIMARY INCREASE
IN LOW-LEVEL AND DEEP-LAYER VERTICAL SHEAR IS EXPECTED THIS
EVENING/OVERNIGHT AS THE MIDLEVEL TROUGH AND SURFACE LOW APPROACH.
THERE WILL BE SOME RISK OF DAMAGING WINDS WITH THE INITIAL STORMS
LATER THIS AFTERNOON...EITHER WITHIN THE PRE-FRONTAL BAND OR MORE
SCATTERED DIURNAL CONVECTION ACROSS N FL...AND THE RISK WILL
CONTINUE INTO TONIGHT WITH A SECOND BOUT OF STORMS POSSIBLE ALONG
THE COLD FRONT /DEPENDING ON THE DEGREE OF STABILIZATION WITH THE
AFTERNOON STORMS/. GIVEN CONCERNS ABOUT PHASING OF INSTABILITY AND
VERTICAL SHEAR...AND THE AFOREMENTIONED MESOSCALE INFLUENCES...WILL
MAINTAIN A LOW-END SLGT RISK.

...E SLOPE SRN/CENTRAL APPALACHIANS TO ERN NY THIS AFTERNOON...
SURFACE TEMPERATURES ARE WARMING INTO THE UPPER 60S-LOWER 70S AS OF
LATE MORNING...AND ADDITIONAL SURFACE HEATING IS EXPECTED E OF A
SURFACE COLD FRONT AND ASSOCIATED CLOUD BAND NOW NEAR THE SPINE OF
THE APPALACHIANS. THOUGH INSTABILITY AHEAD OF THE FRONT WILL LIKELY
REMAIN RATHER WEAK /MLCAPE AOB 500 J PER KG/...A GRADUAL INCREASE IN
SWLY MIDLEVEL FLOW IS EXPECTED FROM VA TO NY IN ASSOCIATION WITH AN
EJECTING MIDLEVEL TROUGH NOW APPROACHING CENTRAL KY/WRN OH. THE
MODEST INSTABILITY...STEEP LOW-LEVEL LAPSE RATES...AND DEEP-LAYER
UNIDIRECTIONAL WIND PROFILES COULD SUPPORT A FEW ORGANIZED
CLUSTERS/LINE SEGMENTS ALONG THE FRONT WITH AN ATTENDANT RISK FOR
ISOLATED STRONG/DAMAGING GUSTS.

..THOMPSON/ROGERS.. 04/21/2012

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