SPC 1200Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1251 AM CDT THU MAY 31 2012 VALID 311200Z - 011200Z ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS OH VALLEY REGION TO MID-SOUTH AND SOUTH TX... ...SYNOPSIS... MID-UPPER LEVEL HEIGHT FALLS ARE FCST FROM UPPER GREAT LAKES TO CENTRAL GULF COAST THIS PERIOD...AS SHORTWAVE TROUGH NOW OVER CENTRAL CONUS AMPLIFIES AND MOVES ESEWD. AREA OF STG CYCLONIC CURVATURE IN WATER-VAPOR PATTERN -- NOW OVER MN -- IS EXPECTED TO EVOLVE INTO AT LEAST MARGINALLY CLOSED 500-MB CYCLONE BY 1/00Z CENTERED NEAR LSE. THIS LOW THEN IS FCST TO PIVOT EWD ACROSS SRN WI TO LM OR ADJACENT LOWER MI BY END OF PERIOD. SRN-STREAM PERTURBATION -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER LOWER CO RIVER VALLEY AND NRN GULF OF CA -- IS FCST TO AMPLIFY AND MOVE SEWD OVER WRN MEX. THIS WILL CONTRIBUTE TO SFC PRESSURE FALLS OVER NRN MEX THAT...IN TURN...HELP TO MAINTAIN ELY FLOW COMPONENT ON BOTH SIDES OF SFC FRONT OVER CENTRAL TX. SFC COLD FRONT -- NOW MOVING SEWD OVER KS AND SWD FROM CENTRAL TO SRN HIGH PLAINS -- WILL SETTLE SWD ACROSS CENTRAL/S TX AND ERN NM THIS PERIOD. FRONT SHOULD REACH UPPER TX COAST...S-CENTRAL TX...LOWER PECOS VALLEY AND EXTREME SRN NM BY 1/12Z...BECOMING QUASISTATIONARY AROUND THAT TIME FROM EDWARDS PLATEAU/LOWER PECOS REGION WNWWD. ERN PART OF FRONT WILL PROGRESS EWD/SEWD OVER MID-UPPER MS VALLEY AND LOWER OH VALLEY...REACHING ERN KY/TN AND CENTRAL/SRN MS BY 1/12Z. THIS WILL OCCUR AS SFC LOW DEEPENS INITIALLY OVER MO...THEN TRACKS IN CYCLONIC ARC ACROSS SRN INDIANA TO NWRN OH. ATTACHED WARM FRONT SHOULD MOVE NEWD ACROSS MID-SOUTH REGION EARLY IN PERIOD...REACHING CENTRAL/NRN KY BY 1/00Z THEN MOVING MORE SLOWLY NEWD OVER OH AND WV. SCATTERED TSTMS IN BANDS AND CLUSTERS SHOULD DEVELOP THIS AFTERNOON NEAR COLD FRONT...FROM OH VALLEY SWWD ACROSS ARKLATEX REGION TO S TX. EXPECT GRADUAL ENVIRONMENTAL TRANSITION OVER ARKLATEX AND E TX BETWEEN REGIMES DESCRIBED BELOW. OVERALL SVR POTENTIAL SHOULD WANE IN BOTH AREAS AFTER DARK AS COMBINATION OF DIABATIC SFC COOLING...OUTFLOW SPREADING...AND POST-FRONTAL CAA CONTRIBUTE TO STABILIZATION. ...OH VALLEY TO MID-SOUTH... TSTMS MAY DEVELOP ALONG/AHEAD OF COLD FRONT DURING MIDDAY/EARLY AFTERNOON HOURS LOCAL TIME...ESPECIALLY NEAR SFC LOW AND ADJOINING COLD/WARM FRONTAL SEGMENTS WHERE SFC CONVERGENCE WILL BE RELATIVELY MAXIMIZED. ADDITIONAL DEVELOPMENT WILL OCCUR FARTHER SW ALONG/AHEAD OF FRONT...ALTHOUGH TIMING IS MORE UNCERTAIN WITH PATCHY COVERAGE...GIVEN 1. MORE WLY/VEERED/WEAKER PREFRONTAL SFC WINDS OVER MID-SOUTH COMPARED TO FARTHER N...LIMITING CONVERGENCE...AND 2. POTENTIAL HINDRANCES TO HEATING DUE TO REMNANT CLOUD COVER FROM CONVECTION FARTHER W. THIS FACTOR ALSO MAY AFFECT OH VALLEY REGION...BUT WOULD BE MORE CRUCIAL HERE GIVEN WEAKER AMBIENT LIFT. TORNADO POTENTIAL APPEARS RELATIVELY MAXIMIZED...FOR EITHER QUASI-LINEAR OR BRIEFLY SUPERCELLULAR MODE...WITHIN LARGE-HODOGRAPH ENVIRONMENT JUST E/SE OF SFC LOW AND INVOF WARM FRONT. THIS AREA WILL BE CHARACTERIZED BY RELATIVELY LARGE LOW-LEVEL BACKING/SRH AND NRN RIM OF AT LEAST MRGL WARM-SECTOR BUOYANCY. DAMAGING GUSTS ARE LIKELY FROM ANY SUSTAINED CONVECTION OVER THIS CORRIDOR...WITH SOME BOW/LEWP STRUCTURES POSSIBLE. ...S TX... ALTHOUGH LOW-LEVEL FORCING MAY BE RATHER WEAK INVOF FRONTAL ZONE...EXISTING LIFT COMBINED WITH INTENSE DIURNAL HEATING SHOULD SUFFICE FOR TSTM FORMATION DURING MID-LATE AFTERNOON. AIR MASS MAY BECOME EXTREMELY BUOYANT AS SFC DEW POINTS MID 60S TO LOW 70S F SUPPORT MLCAPE 3000-4000 J/KG. MAGNITUDE OF LOW-MIDDLE LEVEL FLOW WILL BE MODEST...GENERALLY AOB 15 KT THROUGH MOST OF SFC-550 MB LAYER. HOWEVER...STG VEERING WITH HEIGHT WILL OCCUR...NOT JUST INTO MIDLEVELS BUT FURTHER UPWARD THROUGH CAPE-BEARING LAYER. UPPER-LEVEL/VENTING WINDS WILL INCREASE WITH SWD EXTENT IN PROXIMITY TO SUBTROPICAL JET BRANCH. AS SUCH...SUFFICIENT DEEP-LAYER SHEAR IS EXPECTED TO AT LEAST TRANSIENT/HEAVY-PRECIP SUPERCELL STRUCTURES. LARGE/DAMAGING HAIL IS LIKELY FROM ANY SUCH CONVECTION. POTENTIAL ALSO EXISTS FOR LOCALIZED BUT INTENSE COLD-POOL DEVELOPMENT...WITH WELL-MIXED SUBCLOUD LAYERS SUPPORTING DAMAGING WIND THREAT. ATTM...SPECIFIC NODES OF ENHANCED POTENTIAL NEAR FRONT ARE TOO UNCERTAIN TO DRAW GREATER WIND OR HAIL PROBABILITIES OVER SMALLER AREA. ..EDWARDS/LEITMAN.. 05/31/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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