Thursday, September 13, 2007

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 131732
SWODY2
SPC AC 131730

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT THU SEP 13 2007

VALID 141200Z - 151200Z

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF NE OH...NW PA
AND WRN NY...

..NE OH/NW PA AND WRN NY...
AN UPPER-LEVEL TROUGH OVER THE NRN PLAINS WILL MOVE EWD INTO THE
GREAT LAKES REGION TONIGHT INTO FRIDAY. AT THE SFC...A COLD FRONT
WILL MOVE SEWD INTO THE UPPER OH VALLEY EXTENDING SSWWD INTO THE TN
VALLEY. AHEAD OF THE FRONT ACROSS THE UPPER OH VALLEY...SFC
DEWPOINTS FROM 45 TO 55 F SHOULD RESULT IN WEAK INSTABILITY BY
FRIDAY AFTERNOON. SFC HEATING...STRONG FORCING ASSOCIATED WITH THE
UPPER-LEVEL TROUGH AND LOW-LEVEL CONVERGENCE ALONG THE BOUNDARY
SHOULD ALLOW A LINE OF THUNDERSTORMS TO DEVELOP IN THE VICINITY OF
LAKE ERIE AND NRN OH MOVING SEWD INTO ERN OH...NWRN PA AND WRN NY.
SCATTERED THUNDERSTORMS MAY ALSO DEVELOP ALONG A SECONDARY AXIS OF
INSTABILITY EXTENDING SWD FROM NRN NY INTO CNTRL PA.

FORECAST SOUNDINGS ACROSS THE REGION FRIDAY AFTERNOON SUGGEST
MODERATE VERTICAL SHEAR WILL BE IN PLACE ALONG THE FRONTAL BOUNDARY.

THE VERTICAL SHEAR MAY BE ENOUGH FOR STORM ORGANIZATION ESPECIALLY
IF ENOUGH INSTABILITY DEVELOPS ALONG AND AHEAD OF THE FRONTAL
BOUNDARY. RELATIVELY COLD MID-LEVEL TEMPS MAY PROMOTE A HAIL
POTENTIAL WITH THE STRONGER CELLS.

..TN VALLEY...
THE CENTER OF HUMBERTO IS FORECAST TO BE IN CNTRL MS AT THE
BEGINNING OF THE PERIOD. RAINBANDS ASSOCIATED WITH THE SYSTEM SHOULD
BE LOCATED NORTH AND EAST OF THE CENTER ACROSS NRN MS AND AL WITH
THE RAINBANDS MOVING NEWD INTO TN AND GA BY AFTERNOON. FORECAST
SOUNDINGS ACROSS THE REGION FRIDAY SUGGEST DIRECTIONAL SHEAR JUST
EAST OF THE CENTER WILL BE SUFFICIENT FOR A MARGINAL TORNADO THREAT
ESPECIALLY AS INSTABILITY BECOMES MAXIMIZED IN THE AFTERNOON.

..NE NM/TX PANHANDLE...
A QUASI-STATIONARY FRONT SHOULD BE LOCATED FROM NE NM EXTENDING SEWD
ACROSS THE TX PANHANDLE FRIDAY. SFC DEWPOINTS ALONG THE BOUNDARY
WILL LIKELY BE IN THE 55 TO 60 F RANGE AND MODEL FORECASTS SUGGEST
POCKETS OF MODERATE INSTABILITY MAY DEVELOP BY FRIDAY AFTERNOON. A
WEAKENING CAPPING INVERSION AND INCREASING LOW-LEVEL CONVERGENCE
SHOULD ALLOW SCATTERED THUNDERSTORMS TO DEVELOP IN THE LATE
AFTERNOON. FORECAST SOUNDINGS IN FAR NE NM LATE FRIDAY AFTERNOON
SHOW SUBSTANTIAL DIRECTIONAL SHEAR WITH STEEP MID-LEVEL LAPSE RATES.
THIS MAY SUPPORT A HAIL THREAT WITH THE STRONGER CELLS WITH THE
THREAT STAYING ISOLATED AND MARGINAL.

.BROYLES.. 09/13/2007

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