DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 281933
SWODY1
SPC AC 281931

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0231 PM CDT TUE SEP 28 2010

VALID 282000Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER A SMALL PART OF THE NERN
STATES...

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE UPPER KEYS AND SE
FL...

.CHANGES TO PREV FCST...

1. REDUCE AREAL COVERAGE OF SLGT RISK NERN STATES.

2. ADD SLGT RISK IN SE FL.

...NERN STATES...
MLCAPES TO 500 J/KG AND 0-1KM SRH IN EXCESS OF 175 M2/S2 IN SE NY
AND EXTREME NRN NJ DOWNSTREAM FROM A PRE-FRONTAL TROUGH WILL PROVIDE
A SHORT-TERM THREAT FOR ISOLATED DAMAGING WINDS OR TORNADOES. STORM
MODE WILL FAVOR SHORT-LINE SEGMENTS WITH OCCASIONAL BOWING AS
ACTIVITY MOVES RAPIDLY NNE. AS STRONGER PVA/LLJ CORE SHIFT NWD BY
EVENING...SVR THREATS WILL DIMINISH.

...SE FL/KEYS...
EXPECT SYSTEM S OF CUBA TO BECOME TROPICAL STORM NICOLE THIS
EVENING. NATIONAL HURRICANE CENTER PROGS CENTER OF STORM ON THE N
SHORE OF CNTRL CUBA BY 12Z WEDNESDAY. EVOLVING SPIRAL BANDS WILL
REACH THE KEYS/SE FL LATER TONIGHT COINCIDENT WITH AN INCREASE IN
LLVL WIND FIELDS. FCST SOUNDINGS SUGGEST 0-1KM SRH WILL REACH
175-200+ M2/S2 AFTER 06Z ACROSS THE UPPER KEYS AND SE FL AS NE
QUADRANT OF THE TROPICAL CYCLONE DRAWS CLOSER. THIS WILL ENHANCE
THE RISK OF TORNADOES/WATERSPOUTS AND A SLGT RISK HAS BEEN ADDED.

..RACY.. 09/28/2010

.PREV DISCUSSION... /ISSUED 1108 AM CDT TUE SEP 28 2010/

...NORTHEAST STATES...
A LARGE UPPER TROUGH IS IN PLACE TODAY OVER THE EASTERN
STATES...WHILE A POWERFUL SHORTWAVE TROUGH ROTATES NORTHWARD AROUND
TROUGH ACROSS NY/PA. THE PRIMARY BAND OF LIFT ASSOCIATED WITH THIS
TROUGH EXTENDS FROM CENTRAL NY SOUTHWARD INTO DE/EASTERN MD WHERE
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE OCCURRING. DESPITE
AMPLE LOW LEVEL MOISTURE...WEAK LAPSE RATES AND LIMITED HEATING ARE
YIELDING WEAK INSTABILITY AHEAD OF THE CONVECTION. THIS IS EXPECTED
TO BE THE CASE ALL DAY...LIMITING OVERALL INTENSITY OF ACTIVITY.
NEVERTHELESS...VERTICAL SHEAR PROFILES ARE VERY STRONG WITH 3KM SRH
VALUES OF 200-300 M2/S2 AND EFFECTIVE SHEAR EXCEEDING 50 KNOTS. THE
POTENTIAL WILL EXIST MOST OF THE DAY FOR ISOLATED SUPERCELLS OR BOW
ECHOES CAPABLE OF DAMAGING WINDS OR A BRIEF TORNADO.

FARTHER WEST...BREAKS IN THE CLOUDS AND STEEPENING LOW/MID LEVEL
LAPSE RATES MAY BE SUFFICIENT FOR THE REDEVELOPMENT OF A FEW
THUNDERSTORMS THIS AFTERNOON OVER PORTIONS OF CENTRAL PA/NY. THESE
STORMS WOULD ALSO POSE A RISK OF GUSTY/DAMAGING WINDS PRIOR TO
SUNSET.

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