SPC 0600Z Day 2 Outlook
DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1250 AM CDT SAT MAY 05 2012 VALID 061200Z - 071200Z ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS IL/INDIANA TO ERN OK... ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS NRN FL TO SERN TN... ...SYNOPSIS... SYNOPTIC PATTERN ALOFT WILL BE CHARACTERIZED BY DEAMPLIFYING MS VALLEY RIDGING AND RELATED NET HEIGHT FALLS ACROSS MUCH OF ERN CONUS. PRIMARY SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER INTERIOR PAC NW -- IS FCST TO MOVE EWD ACROSS NRN ROCKIES DAY-1...CONTRACTING INTO CLOSED 500-MB CYCLONE OVER MT/SK BORDER REGION BY START OF PERIOD. LOW SHOULD MOVE EWD ALONG CANADIAN BORDER TO NERN ND OR NWRN MN BY 7/12Z...WITH POSITIVELY TILTED TROUGH SWWD ACROSS WRN SD AND WY. MEANWHILE...WEAKER SHORTWAVE TROUGH WILL MOVE SLOWLY SEWD OVER COASTAL CA AND MAY DEVELOP SMALL/CLOSED 500-MB CYCLONE BY END OF PERIOD OVER OR NEAR SRN PORTIONS CA/NV. PROGS REMAIN QUITE DIFFERENT BY END OF PERIOD REGARDING AMPLITUDE/POSITION OF THIS FEATURE. WEAK/SRN-STREAM PERTURBATION...NOW EVIDENT IN VWP/PROFILER DATA AND SATELLITE IMAGERY OVER WRN AR -- IS FCST TO DRIFT SEWD OVER PORTIONS AL/GA BY 7/12Z...BECOMING PART OF BROAD/WEAK AREA OF CYCLONIC FLOW OVER NERN GULF AND FL. AT SFC...LEE-SIDE LOW NOW OVER CENTRAL HIGH PLAINS IS FCST TO MIGRATE TO SERN SD/NWRN IA AREA BY 6/12Z...COLD FRONT EXTENDING SWWD INTO SECONDARY/FRONTAL-WAVE LOW OVER SRN KS OR NWRN OK. WAVY FRONTAL ZONE -- NOW ANALYZED FROM DELMARVA REGION TO INDIANA AND NEB -- IS EXPECTED TO MOVE SWD AS COLD FRONT ACROSS CAROLINAS TO NRN GA BY START OF PERIOD. BOUNDARY SHOULD BECOME QUASISTATIONARY NWWD OVER TN VALLEY THEN WARM FRONT ACROSS SRN/WRN IL AND IA. FRONTAL POSITION MAY BE MODULATED SOMEWHAT THROUGHOUT PERIOD BY OUTFLOW FROM CONVECTIVE COMPLEXES. BY 7/00Z...WARM FRONT SHOULD LIFT NEWD ACROSS IL AND PORTIONS LOWER OH VALLEY...WHILE COLD FRONT REACHES PORTIONS SERN KS...OK AND NW TX. EVEN BY MIDDLE OF PERIOD...MESOSCALE DISCREPANCIES ARE APPARENT IN PROGGED FRONTAL POSITIONS THAT WILL BE CRUCIAL TO GREATEST SVR PROBABILITIES. ...IL/INDIANA TO ERN OK... SCATTERED TO LOCALLY NUMEROUS TSTMS SHOULD DEVELOP INVOF SFC COLD FRONT DURING AFTERNOON...WHILE CONDITIONAL POTENTIAL FOR SVR CONVECTION EXISTS OVER WARM FRONT. DAMAGING HAIL/GUSTS ARE MAIN SVR THREATS. LACK OF DEEP-LAYER SHEAR OVER MOST OF THIS CORRIDOR SUGGESTS PREDOMINANTLY MULTICELLULAR MODE...ALTHOUGH BRIEF SUPERCELL STRUCTURES ARE POSSIBLE. WARM SECTOR WILL BE CHARACTERIZED COMMONLY BY MID-UPPER 60S SFC DEW POINTS...WITH POCKETS OF 70S F...BENEATH STEEP MIDLEVEL LAPSE RATES. STG SFC DIABATIC HEATING IS EXPECTED WITH MID-LATE AFTERNOON MLCAPE 3500-5000 J/KG IN MUCH OF OUTLOOK AREA. MOST PROBABLE CORRIDOR FOR SUSTAINED/NOCTURNAL CONVECTION APPEARS TO BE NEAR WARM FRONT OVER PORTIONS INDIANA/OH...SVR POTENTIAL DIMINISHING WITH TIME AND EWD EXTENT. GIVEN UNCERTAINTIES IN FRONTAL POSITION/TIMING AND DIFFERENCES IN AREAS OF STRONGEST LOW-LEVEL LIFT...SVR OUTLOOK IS KEPT RATHER BROAD-BRUSHED ATTM. HOWEVER...GIVEN LIKELIHOOD OF STG-EXTREME INSTABILITY ACROSS MUCH OF PREFRONTAL CORRIDOR...30% SVR CONCENTRATION EASILY MAY BECOME APPARENT WITHIN THIS AREA IN SUCCEEDING OUTLOOKS. AS IT STANDS...THREAT EXISTS FOR ISOLATED VERY LARGE/DAMAGING HAIL IN EARLY STAGES OF CONVECTIVE REGIME...ALONG WITH SVR HAIL AND GUSTS AS COVERAGE INCREASES ALONG/AHEAD OF FRONT AND COLD POOLS ACCUMULATE. ...SERN CONUS... RELATIVE CONCENTRATION OF MULTICELLULAR TSTMS...AND OF RELATED SVR POTENTIAL...IS FCST INVOF FRONT DURING AFTERNOON INTO EARLY EVENING FROM NRN FL TO SERN TN. DAMAGING GUSTS AND AT LEAST ISOLATED LARGE HAIL ARE POSSIBLE. LAPSE RATES ALOFT WILL BE RELATIVELY STEEP FOR THIS REGION...WITH STG SFC HEATING AND DEW POINTS UPPER 60S TO LOW 70S CONTRIBUTING TO 2500-3500 J/KG MLCAPE. ALTHOUGH DEEP-TROPOSPHERIC FLOW AND BULK SHEAR ARE EXPECTED TO BE VERY WEAK...POTENTIAL EXISTS FOR TSTMS TO BUILD INTO FORWARD-PROPAGATING COMPLEX WITH ACCORDINGLY ENHANCED WIND THREAT MOVING SWD ACROSS THIS CORRIDOR. ...N-CENTRAL TX TO MID/LOWER RIO GRANDE VALLEY... BY MID-AFTERNOON...DRYLINE SHOULD INTERSECT COLD FRONT OVER CENTRAL OR SRN OK AND EXTEND SSWWD ACROSS CENTRAL TX TO N-CENTRAL/NERN COAHUILA. IN GENERAL...TSTM COVERAGE MAY BE LIMITED BY WEAKER LOW-LEVEL CONVERGENCE AND SOMEWHAT STRONGER EML-RELATED CINH THAN ALONG COLD FRONT. STILL...AT LEAST ISOLATED TSTMS MAY DEVELOP INVOF DRYLINE DURING LATE AFTERNOON...MOVING SLOWLY SEWD. ANY SUSTAINED TSTM MAY PRODUCE SVR HAIL/GUSTS GIVEN LIKELIHOOD OF 4000-5000 J/KG MLCAPE AVAILABILITY. HOWEVER...POTENTIAL APPEARS TOO ISOLATED/CONDITIONAL FOR CATEGORICAL OUTLOOK OVER ENTIRE DRYLINE CORRIDOR ATTM. ..EDWARDS.. 05/05/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day2otlk_0600.html
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