DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 180701
SWODY3
SPC AC 180700

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0200 AM CDT FRI MAY 18 2012

VALID 201200Z - 211200Z

...IL TO NWRN TX...

LATEST SHORT-RANGE MODEL GUIDANCE IS IN GENERAL AGREEMENT REGARDING
THE EVOLUTION OF EJECTING TROUGH DURING THE DAY2/3 TIME FRAME. WITH
UPPER TROUGHING EXPECTED TO HOLD FIRM ACROSS THE SERN U.S...UPSTREAM
FEATURE SHOULD BEGIN TO TURN SEWD ACROSS THE MS VALLEY REGION LATE
WITH A BAND OF MODEST MID LEVEL FLOW EXPECTED TO TRANSLATE ACROSS
THE FRONTAL ZONE OVER THE SRN PLAINS. THIS WILL BE COINCIDENT WITH
STEEPER LAPSE RATES AND SOMEWHAT STRONGER INSTABILITY FROM PORTIONS
OF NWRN TX INTO ERN OK. OTHERWISE...A NARROW CORRIDOR OF HIGHER
MOISTURE WILL EXTEND THE LENGTH OF THE FRONTAL ZONE FROM NWRN TX
THROUGH THE MID MS VALLEY INTO THE UPPER GREAT LAKES.

MODELS AGREE THAT LOW LEVEL CONVERGENCE WILL PROVE GENERALLY WEAK
ALONG THE ADVANCING WIND SHIFT AND BOUNDARY LAYER HEATING SHOULD
PROVE INSTRUMENTAL IN CONVECTIVE DEVELOPMENT ALONG THE
FRONT...ESPECIALLY FROM IL SWWD INTO NWRN TX. THIS PORTION OF THE
BOUNDARY SHOULD EXPERIENCE THE STEEPEST LAPSE RATES AND POTENTIALLY
PRODUCE THE STRONGER UPDRAFTS/DOWNDRAFTS. FOR THIS REASON HAVE
OPTED TO ADD 5% SEVERE PROBS FOR TSTMS THAT DEVELOP ALONG/NEAR THE
COLD FRONT WHERE MARGINAL DEEP LAYER SHEAR WOULD SEEM SUPPORTIVE OF
MULTI-CELL UPDRAFTS AT BEST. ISOLATED GUSTY WINDS AND HAIL WOULD BE
THE MORE SIGNIFICANT THREATS IF ROBUST CONVECTION CAN BECOME
ESTABLISHED DURING THE AFTERNOON/EVENING TIME FRAME.

..DARROW.. 05/18/2012

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