SPC 1200Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1259 AM CDT SAT MAY 26 2012 VALID 261200Z - 271200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MIDWEST TO THE ERN TX PANHANDLE... ...THERE IS A SLGT RISK OF SVR TSTMS FOR ERN WY DURING THE LATE AFTERNOON/EARLY EVENING... ...SYNOPSIS... AMPLIFIED UPPER-LEVEL TROUGH WILL GRADUALLY SHIFT EWD IN THE WRN CONUS AS AN EMBEDDED SHORT WAVE IMPULSE OVER THE SOUTHWEST EJECTS NEWD TOWARDS THE CNTRL ROCKIES. A MID-LEVEL ANTICYCLONE WILL REMAIN ANCHORED OVER THE MID-SOUTH...WHILE SUBTROPICAL STORM BERYL WILL GRADUALLY MOVE SWWD TOWARDS THE S ATLANTIC COAST PER NHC GUIDANCE. AT THE SURFACE...QUASI-STATIONARY FRONT WILL BE DRAPED FROM THE NORTHEAST TO THE MIDWEST. WRN PORTION OF THE FRONT WILL SLOWLY ADVANCE NWD IN THE UPPER MS/MID-MO VALLEYS...WITH PRIMARY LEE CYCLONE EXPECTED TO BE INVOF WY/NEB/CO BORDER AT 27/00Z AND LEE TROUGH EXTENDING SWD TO THE SRN HIGH PLAINS. ...UPPER MIDWEST... LOW CONFIDENCE THIS FORECAST WITH MULTIPLE EPISODES OF TSTMS POSSIBLE...MOST LIKELY WITHIN LOW-LEVEL WAA N OF THE ADVANCING WARM FRONT AS STRONG CAPPING LARGELY INHIBITS SURFACE-BASED CONVECTION WITHIN A VERY UNSTABLE WARM SECTOR. ELEVATED TSTMS SHOULD BE ONGOING AT 12Z ACROSS PARTS OF THE REGION AND MAY PERSIST THROUGH MUCH OF THE DAY WITH AN ATTENDANT SEVERE HAIL THREAT...BUT ALSO BREEDING UNCERTAINTY IN THE NWD ADVANCEMENT OF THE SURFACE FRONT. WITH NEAR-NEUTRAL HEIGHT CHANGE IN THE MID-LEVELS AND THE LACK OF APPARENT UPSTREAM IMPULSES TO AID IN LARGE-SCALE ASCENT...PROSPECTS FOR SURFACE-BASED TSTM INITIATION INVOF THE INTERSECTION OF THE WARM FRONT/EFFECTIVE DRYLINE WILL BE DRIVEN BY SUFFICIENTLY STRONG HEATING. SOME MODELS /SUCH AS THE NAM/ DO SUGGEST THAT TEMPERATURES WILL REACH WELL INTO THE 90S ACROSS CNTRL NEB WHICH WOULD MINIMIZE MLCIN AND MAY YIELD A FEW TSTMS BY LATE AFTERNOON/EARLY EVENING. GIVEN THE LIKELIHOOD OF MLCAPE REACHING 3000-4500 J/KG...DEEP-LAYER SHEAR WOULD BE SUFFICIENTLY FAVORABLE FOR SUPERCELLS WITH ATTENDANT RISKS OF ALL SEVERE TYPES. HAVE EXPANDED SLIGHT RISK SWWD TO ACCOUNT FOR THIS SCENARIO. OTHERWISE...ELEVATED TSTMS SHOULD NOCTURNALLY INCREASE IN COVERAGE WELL N OF THE WARM FRONT AS THE LLJ STRENGTHENS AGAIN WITH A THREAT FOR LARGE HAIL. ...WRN KS TO THE SRN HIGH PLAINS... OPERATIONAL AND CONVECTION-ALLOWING MODELS ARE HIGHLY CONSISTENT IN INDICATING ISOLATED TO SCATTERED TSTMS FORMING ALONG THE LEE TROUGH/DRYLINE THIS AFTERNOON. DEEP-LAYER SHEAR SHOULD REMAIN MODERATE...BUT WITH LARGE SURFACE DEW POINT DEPRESSIONS...A RISK FOR ISOLATED SEVERE WIND/HAIL WILL EXIST. HAVE OPTED TO ADD SLIGHT RISK S/SWWD INTO THE ERN TX PANHANDLE ON THE EDGE OF THE STRONGLY BUOYANT AIR MASS IN NEB/KS/OK. ...ERN WY... FORCING FOR ASCENT WILL INCREASE MARKEDLY AS MID-LEVEL HEIGHT FALLS OVERSPREAD THE LEE OF THE CNTRL ROCKIES RESULTING IN A DEEPENING SURFACE CYCLONE. SHEAR PROFILES N OF THE LOW WILL BECOME STRONG AND VEER SUBSTANTIALLY WITH HEIGHT. GUIDANCE DOES DIFFER ON THE DEGREE OF LOW-LEVEL MOISTENING AND RESULTANT BUOYANCY. HOWEVER...A NARROW AXIS OF AT LEAST LOWER 50S SURFACE DEW POINTS APPEARS PROBABLE. WHILE S OF THIS CORRIDOR...DEEP MIXING WILL RESULT IN INVERTED-V TYPE THERMODYNAMIC PROFILES. GIVEN THE STRENGTH OF THE FORCING AND VERY FAVORABLE DEEP-LAYER SHEAR...WILL OPT TO ADD A SMALL SLIGHT RISK FOR ISOLATED SEVERE HAIL/WIND. ..GRAMS/MOSIER.. 05/26/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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