DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 110600
SWODY2
SPC AC 110558

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1258 AM CDT WED SEP 11 2013

VALID 121200Z - 131200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE PA...NY AND
NEW ENGLAND...

...PA/NY/NEW ENGLAND...
AN UPPER-LEVEL TROUGH WILL MOVE EWD ACROSS THE LOWER GREAT LAKES
REGION ON THURSDAY. AT THE SFC...A COLD FRONT SHOULD ADVANCE SEWD
INTO THE CNTRL AND NRN APPALACHIAN MTNS. THUNDERSTORMS APPEAR LIKELY
TO BE ONGOING ALONG THE FRONT THURSDAY MORNING AND A GENERAL
INCREASE IN CONVECTIVE COVERAGE SHOULD OCCUR DURING THE DAY AS
INSTABILITY INCREASES AHEAD OF THE FRONT. SFC DEWPOINTS IN THE MID
TO UPPER 60S F ACROSS MUCH OF THE NERN STATES SHOULD ALLOW MODERATE
INSTABILITY TO DEVELOP ACROSS A BROAD AREA. THIS COMBINED WITH
WELL-FOCUSED LARGE-SCALE ASCENT AHEAD OF THE UPPER-LEVEL TROUGH
SHOULD ENABLE A SQUALL-LINE OR MULTI-SEGMENTED ORGANIZED LINE OF
STORMS TO MOVE ACROSS THE SLIGHT RISK AREA THURSDAY AFTERNOON.

FORECAST SOUNDINGS AT 21Z THU FROM MAINE SWWD INTO SERN NY SHOW
MLCAPE IN THE 2000 TO 2500 J/KG RANGE WITH 35 TO 40 KT OF 0-6 KM
SHEAR. THIS SHOULD BE ENOUGH TO SUPPORT SUPERCELL DEVELOPMENT MAINLY
WITH DISCRETE CELLS THAT INITIATE AHEAD OF THE DEVELOPING LINE TO
THE WEST. AN ISOLATED TORNADO AND LARGE HAIL THREAT WILL BE POSSIBLE
WITH SUPERCELLS. THE GREATER THREAT COULD BE FOR WIND DAMAGE WITH
THE POTENTIAL MAXIMIZED WHERE INSTABILITY AND LAPSE RATES BECOME
MOST FAVORABLE.

...OH VALLEY...
THE SRN EDGE OF AN UPPER-LEVEL TROUGH AND AN ASSOCIATED COLD FRONT
WILL MOVE ACROSS THE OH VALLEY ON THURSDAY. THUNDERSTORMS ARE
FORECAST TO INITIATE ALONG THE BOUNDARY THURSDAY AFTERNOON WITH
SEVERAL CLUSTERS OF STORMS MOVE SEWD ACROSS THE OH VALLEY. FORECAST
SOUNDINGS AT 21Z ACROSS KY ALONG AND TO THE SOUTH OF THE BOUNDARY
SHOW SFC DEWPOINTS AROUND 70 F WITH MLCAPE VALUES REACHING THE 1500
TO 2000 J/KG RANGE. THIS COMBINED WITH 0-3 KM LAPSE RATES AROUND 8.0
C/KM SHOULD BE ENOUGH FOR MARGINALLY SEVERE WIND GUSTS WITH THE
STRONGER MULTICELLS. AT THIS POINT...MODEL FORECASTS DIFFER SOME
CONCERNING THE AMOUNT OF DEEP LAYER SHEAR THAT WILL BE AVAILABLE TO
CONVECTION ACROSS THE OH VALLEY THURSDAY AFTERNOON. THE GFS IS THE
LESS AGGRESSIVE SOLUTION. IF THE MORE AGGRESSIVE NAM ENDS UP PANNING
OUT...THEN AN UPGRADE TO SLIGHT RISK COULD BECOME NECESSARY IN LATER
OUTLOOKS.

..BROYLES.. 09/11/2013

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