DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 311937
SWODY1
SPC AC 311935

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0235 PM CDT MON OCT 31 2011

VALID 312000Z - 011200Z

...NO SVR TSTM AREAS FORECAST...

HAVE REINTRODUCED A SMALL GENERAL TSTM AREA FOR PARTS OF OH...AS
ISOLATED TSTMS HAVE DEVELOPED WITHIN A STEEP LAPSE RATE ENVIRONMENT
IN ASSOCIATION WITH A MID-LEVEL TROUGH OVER NWRN OH. ANY TSTM THREAT
HERE SHOULD BE SHORT-LIVED...AS ACTIVITY WILL LIKELY DIMINISH
RAPIDLY BY 00Z WITH THE ONSET OF NOCTURNAL COOLING.

ELSEWHERE...ADJUSTED GENERAL TSTM LINE IN FL TO ACCOUNT FOR LATEST
COLD FRONT POSITION. OTHERWISE PREVIOUS FORECAST REASONING REMAINS
VALID.

..GRAMS.. 10/31/2011

.PREV DISCUSSION... /ISSUED 1111 AM CDT MON OCT 31 2011/

...SYNOPSIS...
A MIDLEVEL SHORTWAVE TROUGH OVER THE OH VALLEY...WITH A LOBE
EXTENDING SWD TO THE NE GULF OF MEXICO...WILL PROGRESS EWD TO THE
ATLANTIC COAST TONIGHT. CYCLOGENESIS IS EXPECTED IN ADVANCE OF THIS
TROUGH...ALONG A PRE-EXISTING FRONT THAT STRETCHES FROM THE SE GULF
ACROSS S FL AND INTO THE WRN ATLANTIC. A MOIST AND WEAKLY UNSTABLE
WARM SECTOR /MLCAPE OF 500-1000 J PER KG/ IS LOCATED S OF THE FRONT
IN FL...WHERE A FEW BANDS/CLUSTERS OF THUNDERSTORMS ARE ONGOING.
MORNING SURFACE OBSERVATIONS AND RADAR IMAGERY ALREADY SHOW EVIDENCE
OF THE SURFACE WAVE FORMATION JUST OFF THE E CENTRAL FL COAST...AND
LOW-LEVEL FLOW/SHEAR ARE EXPECTED TO WEAKEN ACROSS S FL AS THE WAVE
MOVES NEWD AWAY FROM FL. THUS...IT APPEARS THAT THE RISK FOR
ORGANIZED SEVERE STORMS WILL SLOWLY DIMINISH THROUGH THE
AFTERNOON/EVENING.

ELSEWHERE...STEEP LAPSE RATES WILL ACCOMPANY THE MIDLEVEL TROUGH
OVER THE OH VALLEY THIS AFTERNOON. SURFACE HEATING IN CLOUD BREAKS
AND RESIDUAL BOUNDARY LAYER DEWPOINTS OF 35-40 F COULD SUPPORT
SBCAPE NEAR 100 J/KG...AND SHALLOW CONVECTION IS EXPECTED IN THIS
ENVIRONMENT ACROSS WRN OH IN THE ZONE OF ASCENT PRECEDING THE
MIDLEVEL TROUGH...AND ALONG A WEAK SURFACE TROUGH.
HOWEVER...INSTABILITY APPEARS TOO MARGINAL TO WARRANT THE
REINTRODUCTION OF A THUNDERSTORM OUTLOOK AREA ACROSS THE OH VALLEY.
THE RISK FOR ISOLATED THUNDERSTORMS MAY INCREASE SOME BY THIS
EVENING/TONIGHT ACROSS ERN NC AS THE OH VALLEY TROUGH ENCOUNTERS THE
NW EDGE OF THE RICHER MOISTURE PLUME NEAR THE SE ATLANTIC COAST.

FARTHER W...THERE WILL BE SOME RISK FOR WEAK MIDLEVEL CONVECTION
TONIGHT FROM NRN NV INTO NW UT. HERE...STEEP MIDLEVEL LAPSE RATES
AND FRONTOGENESIS WILL BE SUPPORTIVE OF AN E-W PRECIPITATION BAND
WITH SOME EMBEDDED CONVECTION. STILL...VERY MARGINAL INSTABILITY
/MUCAPE AOB 100 J PER KG/ WILL PRECLUDE THE NEED FOR AN OUTLOOK
AREA.

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