DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 220547
SWODY2
SPC AC 220545

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1245 AM CDT WED AUG 22 2012

VALID 231200Z - 241200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
TWO WEAK SHORT WAVE IMPULSES SHOULD GRADUALLY PROGRESS EWD...ONE
ACROSS THE SRN PRAIRIE PROVINCES/UPPER MS VALLEY AND THE OTHER
ACROSS THE SOUTHWEST. A MORE VIGOROUS SHORT WAVE TROUGH WILL AMPLIFY
ACROSS BRITISH COLUMBIA INTO THE FAR NORTHWEST. AT THE SURFACE...A
TROUGH/EFFECTIVE DRYLINE SHOULD STALL FROM THE ERN DAKOTAS TO THE
CNTRL HIGH PLAINS ON THU AFTERNOON.

...UPPER MIDWEST TO THE TX/OK PANHANDLES...
ALONG THE STALLED SURFACE TROUGH...A STRONG LLJ WED NIGHT WILL
PROMOTE MOISTURE TRANSPORT AND SHOULD YIELD INCREASING POTENTIAL
BUOYANCY BY THU AFTERNOON. MOST NCEP GUIDANCE APPEARS TO BE OF VERY
POOR QUALITY WITH THE DEGREE OF LOW-LEVEL MOISTENING...BASED ON
CURRENT OBSERVATIONS COMPARED TO MODEL INITIALIZATIONS. THE GFS AND
SREF MEAN...WHICH IS PREDOMINATELY INFLUENCED BY WRF-NMM/ARW THAT
ARE INITIALIZED BY THE GFS/RAP RESPECTIVELY...DEPICT SURFACE DEW
POINTS/MEAN MIXING RATIOS THAT APPEAR SUBSTANTIALLY TOO HIGH. THE
DRIER SPECTRUM OF GUIDANCE...SUCH AS THE NAM...APPEAR MORE
APPROPRIATE FOR THE SYNOPTIC PATTERN WHICH SUGGESTS MIDDLE 50S TO
LOWER 60S SURFACE DEW POINTS SHOULD BE PREVALENT ALONG THE TROUGH ON
THU AFTERNOON. THIS SHOULD YIELD MODERATE BUOYANCY WITH MLCAPE
REACHING 1000-2000 J/KG.

GIVEN PERSISTENT LOW-LEVEL SLYS...CONVERGENCE SHOULD BE SUFFICIENT
TO FORCE AREAS OF TSTMS ALONG THE TROUGH BY LATE AFTERNOON AS MLCIN
WEAKENS. ALTHOUGH DEEP-LAYER FLOW FIELDS WILL GENERALLY REMAIN
MODEST...VEERING OF THE WIND PROFILE WITH HEIGHT SHOULD RESULT IN
EFFECTIVE SHEAR FROM AROUND 20-30 KT. THIS WILL SUPPORT MULTICELL
CLUSTERS PERSISTING INTO THE EVENING WITH THREATS OF LOCALIZED
SEVERE HAIL/WIND.

..GRAMS.. 08/22/2012

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