DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 180542
SWODY1
SPC AC 180539

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1239 AM CDT MON MAY 18 2009

VALID 181200Z - 191200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
A LARGE MID-LEVEL RIDGE IS FORECAST TO EXPAND INTO THE CENTRAL 2/3
OF THE CONUS THIS PERIOD...BETWEEN AN ADVANCING NWRN U.S. TROUGH AND
A DEPARTING TROUGH OVER THE ERN CONUS.

IN RESPONSE TO THE TROUGH CROSSING THE ERN CONUS...A COLD FRONT WILL
CONTINUE SAGGING SWD ACROSS FL. IN THE WEST...A BAROCLINIC ZONE
WILL LINGER/MOVE SLOWLY SWD ACROSS THE NRN INTERMOUNTAIN REGION AND
N CENTRAL STATES THROUGH THE PERIOD.

...FL...
MOIST/DESTABILIZING AIRMASS THROUGH THE AFTERNOON S OF A SLOWLY
ADVANCING COLD FRONT SHOULD YIELD AFTERNOON THUNDERSTORM DEVELOPMENT
ACROSS CENTRAL/S FL. WHILE DEEP-LAYER WIND FIELD IS FORECAST TO
VEER WITH HEIGHT...OVERALL MAGNITUDE OF THE FLOW IS EXPECTED TO
REMAIN MODEST. THUS...ONLY WEAK ORGANIZATION APPEARS LIKELY -- BUT
POTENTIAL APPEARS SUFFICIENT TO SUPPORT A CONTINUATION OF LOW SEVERE
PROBABILITY ACROSS ROUGHLY THE SRN 2/3 OF THE PENINSULA.

...UPPER MS VALLEY...
SHOWERS AND A FEW THUNDERSTORMS SHOULD DEVELOP ALONG A SEWD-MOVING
FRONT DURING THE LATE AFTERNOON...AS MINIMAL INSTABILITY DEVELOPS
NEAR PEAK HEATING. WHILE OVERALL LACK OF INSTABILITY SHOULD LIMIT
THE NUMBER OF STORMS...MODERATE NWLY FLOW ALOFT SUGGESTS A
LOW-PROBABILITY POTENTIAL ISOLATED/DAMAGING GUSTS THROUGH EARLY
EVENING.

...MT...
MODEST DESTABILIZATION IS FORECAST ACROSS MT NEAR AND S OF A
BAROCLINIC ZONE FORECAST TO SAG SLOWLY SWD WITH TIME. MODELS
INDICATE INCREASING ELY FLOW ACROSS MT NEAR/N OF THE FRONT...WITH
RESULTING UPSLOPE-INDUCED UVV EXPECTED TO INITIATE SHOWERS AND
ISOLATED THUNDERSTORMS. WITH 40 KT MID-LEVEL WLYS ACROSS THIS
REGION...SOME POTENTIAL FOR UPDRAFT ORGANIZATION EXISTS. THOUGH
ISOLATED NATURE OF THE STRONGER STORMS SHOULD GREATLY THE OVERALL
THREAT...WILL MAINTAIN LOW PROBABILITY SEVERE THREAT ACROSS THIS
REGION.

..GOSS/GRAMS.. 05/18/2009

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