SPC 1200Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1259 AM CDT THU MAY 03 2012 VALID 031200Z - 041200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM MID-MO VALLEY TO THE GREAT LAKES TODAY THROUGH TONIGHT... ...THERE IS A SLGT RISK OF SVR TSTMS FOR THE EDWARDS PLATEAU THU AFTERNOON/EVENING... ...SYNOPSIS... BROAD LOW-AMPLITUDE CYCLONIC FLOW WILL PERSIST OVER THE NWRN/N-CNTRL CONUS WITH A SERIES OF EMBEDDED WEAK IMPULSES. MID-LEVEL SPEED MAX OVER THE NRN HIGH PLAINS SHOULD BECOME CENTERED ALONG THE MN/ONTARIO BORDER BY THIS AFTERNOON. NEXT IDENTIFIABLE IMPULSE OFF THE PACIFIC NW COAST WILL MOVE E THEN NEWD TOWARDS THE NRN ROCKIES IN THE CONUS/SWRN CANADA...WITH ASSOCIATED SPEED MAX BECOMING CENTERED FROM THE NRN GREAT BASIN TO THE CNTRL ROCKIES. AT THE SURFACE...A QUASI-STATIONARY FRONT SHOULD REMAIN ACROSS THE UPPER MIDWEST...WITH CONVECTIVELY-GENERATED OUTFLOWS FROM WED NIGHT/THU MORNING SERVING AS THE PRIMARY FOCI FOR DIURNALLY-DRIVEN TSTMS ON THU. A WEAK SURFACE CYCLONE SHOULD DEVELOP IN CNTRL KS WITH THE DRYLINE EXTENDING S/SWWD TO THE EDWARDS PLATEAU OF WRN TX. IN THE SRN STREAM...AN UPPER-LEVEL TROUGH OFF BAJA CA WILL DAMPEN AS IT EJECTS NEWD ACROSS NWRN MEXICO TOWARDS THE SRN HIGH PLAINS BY EARLY FRI. ...MID-MO VALLEY TO THE GREAT LAKES... LOW CONFIDENCE EXISTS WITH DETAILED CONVECTIVE EVOLUTION ON D1 OWING TO CLUSTERS OF TSTMS LIKELY ONGOING AT 12Z FROM THE CORN BELT TO THE GREAT LAKES...AND LACK OF IDENTIFIABLE UPSTREAM IMPULSES WITHIN A BROAD FETCH OF MODERATE MID-LEVEL SWLYS. SOME OF THIS ACTIVITY SHOULD PERSIST THROUGH THE DAY SUPPORTED BY CONTINUED ISENTROPIC ASCENT WITHIN THE QUASI-STATIONARY FRONTAL ZONE AND DIURNAL DESTABILIZATION AS THE WARM SECTOR S OF THE ONGOING ACTIVITY BECOMES MODERATE TO STRONGLY UNSTABLE. THESE STORMS WILL POSE A RISK FOR ISOLATED SEVERE HAIL/WIND. ADDITIONAL STORMS SHOULD DEVELOP BY PEAK HEATING INTO EARLY EVENING ALONG LEFTOVER CONVECTIVELY-GENERATED OUTFLOWS SWWD TOWARDS A SURFACE CYCLONE IN CNTRL KS. THE GREATEST POTENTIAL INSTABILITY IS EXPECTED WITH SWRN EXTENT IN THE CNTRL PLAINS BUT WITH STRONGER CAPPING. SHOULD STORMS FORM HERE...MLCAPE OF 3000-4000 J/KG WOULD BE SUFFICIENT FOR POTENTIALLY VERY LARGE HAIL. OTHERWISE...ONE OR MORE MCS CLUSTERS ARE ANTICIPATED TO EVOLVE E/SEWD FROM THE GREAT LAKES TO THE MID-MO VALLEY DURING THE LATE AFTERNOON AND EVENING WITH WIDELY SCATTERED OCCURRENCES OF SEVERE WIND/HAIL. ...EDWARDS PLATEAU AREA OF WRN TX... WITH APPROACH OF A DAMPENING UPPER-LEVEL TROUGH FROM BAJA CA...BOTH OPERATIONAL AND CONVECTION-ALLOWING MODEL GUIDANCE ARE FAIRLY CONSISTENT THAT CONVECTION WILL BE MORE PREVALENT RELATIVE TO WED OVER THE MTNS OF COAHUILA AND PERHAPS ALONG AND E OF THE DRYLINE IN THE EDWARDS PLATEAU. SHOULD STORMS FORM IN TX...A BELT OF ENHANCED MID-LEVEL SWLYS ACCOMPANYING THE IMPULSE WOULD RESULT IN SUFFICIENT DEEP-LAYER SHEAR FOR MARGINAL SUPERCELL STRUCTURES WITH ISOLATED SEVERE HAIL/WIND. ...CNTRL HIGH PLAINS... BOUNDARY LAYER MOISTENING WITH WEAK UPSLOPE FLOW SHOULD AID IN AT LEAST ISOLATED HIGH BASED TSTMS FORMING ALONG A LEE TROUGH BY LATE AFTERNOON. ALTHOUGH BUOYANCY WILL REMAIN MEAGER...STEEP LOW/MID-LEVEL LAPSE RATES AND EFFECTIVE SHEAR STRENGTHENING TO AROUND 40 KT...SHOULD SUPPORT A RISK FOR MARGINALLY SEVERE WIND/HAIL. ..GRAMS/HURLBUT.. 05/03/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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