Saturday, September 24, 2011

DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 240701
SWODY3
SPC AC 240700

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0200 AM CDT SAT SEP 24 2011

VALID 261200Z - 271200Z

...OH VALLEY...

LATEST MODEL GUIDANCE BEGINS TO DIFFER REGARDING THE TIMING/SPEED OF
EJECTING UPPER LOW FROM IA/MO/IL. GFS IS CONSIDERABLY FASTER THAN
THE NAM WITH THE CENTER OF THE UPPER LOW FORECAST INTO EXTREME SWRN
LOWER MI WHILE THE LATTER HOLDS THE CYCLONE OVER SERN IA. THE
LATEST ECMWF WOULD SEEM TO SUPPORT A COMPROMISE OF THESE TWO
SOLUTIONS WITH A POSITION OVER NERN IL AT 27/00Z. GIVEN THAT
INSTABILITY WILL LIKELY BE SOMEWHAT MARGINAL AHEAD OF THIS FEATURE
WILL NOT INTRODUCE SEVERE PROBS TO THE DAY3 PERIOD.
HOWEVER...ADEQUATE DEEP LAYER SHEAR WILL OVERSPREAD THE ADVANCING
SFC FRONT ACROSS THE OH VALLEY AND CONVECTION WILL LIKELY DEVELOP
ALONG THE COLD FRONT AS IT PROGRESSES ACROSS THE REGION. AS
DIFFERENCES IN THE LATEST MODEL GUIDANCE ARE RESOLVED IT MAY BE
NECESSARY TO ADD A LOW RISK OF SEVERE TO PORTIONS OF THE OH VALLEY.

..DARROW.. 09/24/2011

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