DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 241640
SWODY2
SPC AC 241639

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1139 AM CDT MON SEP 24 2012

VALID 251200Z - 261200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
MID-UPPER LEVEL PATTERN DEAMPLIFICATION IS FCST TO CONTINUE ACROSS
CONUS THROUGH PERIOD...AS ERN HUDSON BAY-AREA VORTEX DEVOLVES TO
OPEN WAVE AND MOVES EWD ACROSS NRN QUE. GEN CYCLONIC-FLOW REGIME
WILL PERSIST ACROSS GREAT LAKES AND NEW ENGLAND...MOSTLY RELATED TO
SPEED MAX/VORTICITY BANNER NOW EVIDENT OVER WRN/NWRN SHORE OF HUDSON
BAY. THIS FEATURE SHOULD PIVOT SEWD/EWD AND AMPLIFY...WITH
STG/POSITIVE-TILT SHORTWAVE TROUGH CROSSING LS...LM...AND UPPER MI
DURING LATTER HALF OF PERIOD. MEANWHILE...SMALL MID-UPPER LEVEL
CYCLONE -- NOW SLOWLY FILLING AS IT MOVES SEWD ACROSS NWRN GREAT
BASIN REGION -- IS EXPECTED TO PIVOT EWD ACROSS UT AND WRN CO
THROUGH DAY-2...WHILE CONTINUING SLOW WEAKENING TREND.
SEPARATE/NRN-STREAM PERTURBATION -- NOW EVIDENT IN MOISTURE CHANNEL
IMAGERY APCHG BC COAST -- SHOULD MOVE ESEWD ACROSS CANADIAN ROCKIES
AND ID PANHANDLE BY 26/00Z...TO SRN AB AND NRN MT BY 26/12Z.

AT SFC...COLD FRONT NOW OVER NWRN ONT...NWRN MN AND ND IS FCST TO
SWEEP SEWD TO 24/12Z POSITION NEAR NRN LH...SRN WI...CENTRAL/SRN
IA...NERN/CENTRAL KS...AND OK PANHANDLE. BY 25/00Z...FRONT SHOULD
EXTEND ROUGHLY FROM SRN LH TO NRN IL...NRN MO...ERN/SRN KS...THROUGH
WEAK FRONTAL-WAVE LOW OVER TX PANHANDLE...TO ERN PORTIONS CO/NM
BORDER.

...ERN KS TO MID/LOWER OH VALLEY REGION...
ONLY MINOR/SUPERFICIAL CHANGES TO THUNDER AND MRGL-SVR PROBABILITIES
ACROSS THIS AREA...AS PROGS HAVE BEEN RATHER CONSISTENT RUN-TO-RUN
INTO LATEST/12Z GUIDANCE FOR FRONTAL POSITION AND CONVECTIVE
POTENTIAL OVER THIS SWATH. SCATTERED AFTERNOON/SFC-BASED TSTMS MAY
BE FOCUSED ON RELATED DIFFERENTIAL-HEATING ZONES AS MUCH AS FRONT
ITSELF. CORRIDOR OF 60S F SFC DEW POINTS SHOULD BE IN PLACE BY
MID-LATE AFTERNOON...THANKS TO PRIOR MOIST
ADVECTION/TRANSPORT...SUPPORTING MLCAPE 800-1500 J/KG IN FCST
SOUNDINGS. SOME BACKING OF WINDS OVER ERN IL AND INDIANA...RELATED
TO WEAK FRONTAL WAVE OVER IL...MAY ENHANCE LOW-LEVEL HODOGRAPHS
ENOUGH TO OFFER AT LEAST BRIEF SUPERCELL POTENTIAL...WITH ATTENDANT
RISK OF WIND/HAIL. MAIN UNCERTAINTY IN DIURNAL DESTABILIZATION AND
SVR POTENTIAL WILL BE PERSISTENCE OF CLOUDS/PRECIP LEFT OVER FROM
MORNING ACTIVITY.

IN AND NEAR FRONTAL ZONE...MID-UPPER LEVEL WINDS...DEEP-LAYER SHEAR
AND LOW-LEVEL SHEAR ALL ARE FCST TO WEAKEN WITH WSWWD EXTENT...AS
DISTANCE INCREASES FROM GREAT-LAKES CYCLONIC FLOW BELT ALOFT.
MEANWHILE...WARMER AND MORE WELL-MIXED SUBCLOUD LAYER WILL
CHARACTERIZE PREFRONTAL AIR MASS OVER KS/OK...SUPPORTING POTENTIAL
FOR STG GUSTS DURING RELATIVELY BRIEF TIME WINDOW OF LATE AFTERNOON
AND EARLY EVENING. WHILE WRN EDGE OF ACTUAL SVR POTENTIAL IS
NECESSARILY MORE FUZZY THAN CAN BE DRAWN USING LINES...ORGANIZATION
OF CONVECTION AND CONDITIONALITY OF SVR RISK EACH APPEAR TOO LOW FOR
AOA 5% PROBABILITIES W OF ERN KS ATTM.

..EDWARDS.. 09/24/2012

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