SWODY1
SPC AC 030600
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT SAT SEP 03 2011
VALID 031200Z - 041200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS LOWER MI TO IA/MO...
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL GULF COAST AND
LOWER DELTA REGION...
...SYNOPSIS...
MID-UPPER LEVEL PATTERN WILL BE DOMINATED BY ANTICYCLONE CENTERED
OVER NM...WHILE RIDGING EXTENDING ENEWD ACROSS OK/KY PERSISTS BUT
WEAKENS. STRENGTHENING CYCLONIC FLOW AND HEIGHT FALLS ALOFT ARE
FCST ACROSS MUCH OF UPPER MIDWEST REGION AND UPPER MS VALLEY...AHEAD
OF SHORTWAVE TROUGH NOW OVER PORTIONS SRN SK AND NRN MT. THIS
TROUGH SHOULD MOVE ESEWD AND AMPLIFY THROUGH PERIOD...REACHING NWRN
ONT...NRN MN AND CENTRAL-WRN SD BY 4/00Z...THEN LS...CENTRAL WI AND
NRN IA BY 4/12Z.
ASSOCIATED SFC COLD FRONT -- NOW ANALYZED FROM N-CENTRAL ND TO
W-CENTRAL SD AND E-CENTRAL/SERN WY -- WILL MOVE SEWD TO VICINITY WRN
UPPER MI...CENTRAL WI...NRN MO...NWRN OK AND SRN PANHANDLE OF TX BY
4/00Z...THEN FROM LOWER MI TO SRN IL TO SRN OK TO PERMIAN BASIN OF W
TX BY END OF PERIOD. QUASISTATIONARY FRONTAL ZONE -- NOW ANALYZED
FROM LOWER MI WSWWD ACROSS IA...SERN NEB AND SWRN KS -- IS EXPECTED
TO LIFT NEWD AS WARM FRONT OVER WI...LM AND LOWER MI...WHILE WESTERN
PORTIONS ARE OVERTAKEN BY AFOREMENTIONED COLD FRONT.
...UPPER GREAT LAKES TO LOWER MO VALLEY...
SCATTERED TSTMS WITH POTENTIAL FOR HAIL/GUSTS NEAR SVR LIMITS MAY BE
ONGOING AT START OF PERIOD OVER SERN SD/NERN NEB/NWRN IA/SERN MN
REGION...PERHAPS AS ERN SHIFT/EXTENSION OF ACTIVITY PRESENTLY
EVIDENT OVER SWRN SD. HOWEVER...GREATEST CONCENTRATION OF BOTH
TSTMS AND SVR POTENTIAL MAY BE DURING AFTERNOON/EVENING OVER
CATEGORICAL OUTLOOK AREA...MAIN CONCERNS BEING DAMAGING GUSTS AND
OCNL LARGE HAIL. THIS SHOULD OCCUR AS COLD FRONT CROSSES ONE
SEGMENT OF OLDER/RESIDUAL FRONTAL ZONE OVER ERN IA/NRN IL/SRN WI
REGION AND IMPINGES UPON RELATIVELY UNDISTURBED/ANTECEDENT WARM
SECTOR. THIS AIR MASS WILL BE CHARACTERIZED BY PLUME OF SFC DEW
POINTS 70S F AND STG SFC HEATING...ALONG WITH STEEP MIDLEVEL LAPSE
RATES...CONTRIBUTING TO MLCAPE 2000-3000 J/KG THAT MAY BRIEFLY GO
HIGHER LOCALLY. LOW-LEVEL FLOW IS FCST TO REMAIN WEAK...KEEPING
BOUNDARY-LAYER SHEAR VECTORS AND HODOGRAPHS RATHER SMALL.
HOWEVER...SRN RIM OF 55-65 KT 250-MB JET MAX SHOULD OVERLIE MERGING
FRONTAL ZONES IN THIS AREA...CONTRIBUTING TO ENHANCED SHEAR THROUGH
CAPE LAYER. UPSCALE GROWTH OF THIS ACTIVITY AND/OR ADDITIONAL
DEVELOPMENT FARTHER E WILL EXPAND SVR THREAT ACROSS LM TO LOWER MI.
...CENTRAL GULF COAST AND LOWER DELTA REGION...
EXPECT NET INCREASE TODAY IN TORNADO POTENTIAL...COMPARED TO PRIOR
DAY-1 PERIOD...WITH SOME INLAND EXPANSION OF AT LEAST
MRGL/CONDITIONAL THREAT. 0-1 KM AGL HODOGRAPHS...SRH AND SHEAR
VECTORS SHOULD REMAIN AT LEAST MRGLLY FAVORABLE AS THEY HAVE
BEEN...PERHAPS ENLARGING SOMEWHAT IF SYSTEM INTENSIFIES AS FCST BY
NHC. GRADUAL INCREASE IN LOW-LEVEL BUOYANCY IS POSSIBLE ESPECIALLY
ACROSS NEAR-COASTAL AREAS...AS EXPANSIVE PRECIP SHIELD AND RELATED
SUBTLE THETAE DEFICIT THAT HAS MINIMIZED CAPE SO FAR SHIFTS INLAND
IN STEP WITH BOTH EXPANSION AND TRANSLATIONAL MOVEMENT OF TROPICAL
CYCLONE. REF LATEST NHC ADVISORIES FOR FCST GUIDANCE ON TS LEE.
...S-CENTRAL PLAINS...
WIDELY SCATTERED TO SCATTERED TSTMS MAY PRODUCE HAIL AND GUSTS NEAR
SVR LEVELS IN A FEW LOCALES NEAR FRONT...PRIMARILY MID-LATE
AFTERNOON INTO EARLY EVENING. CONVERGENCE ALONG FRONT IS FCST TO
DIMINISH AS IT MOVES SWD OVER SRN KS...OK AND W TX THROUGH
MIDDLE-LATTER PART OF PERIOD...GIVEN INCREASING NLY COMPONENT OF
PREFRONTAL SFC WINDS RELATED TO PERIPHERAL INFLUENCES OF TS LEE.
HOWEVER...WIDELY SCATTERED TSTMS SHOULD FORM ALONG FRONT OVER
PORTIONS KS/NW OK...AND BEHIND FRONT IN UPSLOPE FLOW REGIME OVER
SERN CO AND NERN NM...DURING MID-LATE AFTERNOON. THREAT SHOULD
DIMINISH QUITE QUICKLY DURING EVENING...RELATED BOTH TO
AFOREMENTIONED LOSS OF FRONTAL CONVERGENCE AND TO DIABATIC SFC
COOLING/STABILIZATION.
...CENTRAL-NRN APPALACHIANS...
WIDELY SCATTERED TSTMS SHOULD DEVELOP DURING STG AFTERNOON HEATING
OF HIGHER TERRAIN...WHERE MLCINH WILL BE ERODED FASTEST. FAVORABLE
SFC MOISTURE -- I.E. DEW POINTS LOW-MID 60S AT HIGHER ELEVATIONS AND
UPPER 60S TO LOW 70S AT LOWER LEVELS -- WILL CONTRIBUTE TO
DEVELOPMENT OF CORRIDOR OF 1000-2500 J/KG MLCAPE. MAIN LIMITING
FACTOR FOR ORGANIZED SVR POTENTIAL WILL BE LACK OF MORE ROBUST
LOW-MIDDLE LEVEL FLOW...KEEPING SHEAR WEAK. MAIN CONCERN WILL BE
MULTICELLULAR OR PULSE GUSTS NEAR SVR LEVELS...THOUGH ISOLATED HAIL
ALSO CANNOT BE RULED OUT.
..EDWARDS/HULRBUT.. 09/03/2011
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