SPC 1630Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1128 AM CDT WED MAY 23 2012 VALID 231630Z - 241200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MIDWEST AND CENTRAL PLAINS INTO NERN CO... ...THERE IS A SLGT RISK OF SVR TSTMS OVER ERN PARTS OF THE CAROLINAS INTO SERN VA... ...UPPER MIDWEST INTO THE CENTRAL PLAINS... UPPER LOW OVER SRN CANADIAN PRAIRIES IS FORECAST TO REMAIN QUASI-STATIONARY THROUGH THE PERIOD AS SEVERAL PERTURBATIONS PROGRESS EWD WITHIN THE BAND OF THE STRONG MID/UPPER LEVEL WINDS FROM THE GREAT BASIN INTO THE PLAINS. WATER VAPOR IMAGERY SHOWS ONE SHORT WAVE TROUGH FROM ERN WY INTO NERN UT...AND THIS IS EXPECTED TO MOVE INTO THE PLAINS TONIGHT AND PROVIDE INCREASING SUPPORT FOR CONVECTIVE DEVELOPMENT. AT THE SURFACE...A COLD FRONT FROM THE ERN DAKS/MN BORDER SWWD INTO NWRN KS AND CENTRAL CO IS EXPECTED TO MOVE SLOWLY EWD/SEWD AS INCREASING SWLY FLOW ALOFT BECOMES MORE PARALLEL TO THE FRONTAL ORIENTATION. 12Z SOUNDINGS SHOW A VERY WELL-DEFINED EML OVER THE PLAINS WITH VERY WARM 700 MB TEMPERATURES OF 15C AT LBF...DDC AND AMA. THE EML IS LIKELY TO INHIBIT SURFACE-BASED CONVECTIVE DEVELOPMENT AHEAD OF THE FRONT...WITH MODEL GUIDANCE GENERALLY INDICATING THAT STORMS WILL INITIATE ALONG/BEHIND THE FRONT LATER THIS AFTERNOON FROM SWRN MN SWWD INTO ERN NEB. MOISTURE CONTINUES TO BE MODEST WITH PW VALUES OF 1.0-1.25 INCHES AND SURFACE DEW POINTS REMAINING IN THE 55-60F RANGE. VERY STEEP LAPSE RATES ARE EXPECTED TO DEVELOP THROUGH A DEEP LAYER AHEAD OF THE FRONT AS STRONG DIABATIC HEATING STEEPENS LOW LEVEL LAPSE RATES RESULTING IN A DEEP WELL-MIXED BOUNDARY LAYER. STRENGTHENING MID/UPPER LEVEL WINDS WILL GRADUALLY OVERSPREAD THE CENTRAL PLAINS INTO THE UPPER MIDWEST...CONTRIBUTING TO 40-50 KT DEEP LAYER SHEAR SUPPORTIVE OF ORGANIZED CONVECTIVE STRUCTURES INCLUDING SUPERCELLS. VERY LARGE HAIL AND DAMAGING WIND GUSTS WILL BE THE PRIMARY SEVERE THREATS FROM LATE AFTERNOON THROUGH THE EVENING HOURS...ALTHOUGH AN ISOLATED TORNADO OR TWO MAY ALSO BE POSSIBLE FOR STORMS THAT FORM CLOSE TO THE FRONT. ACTIVITY IS EXPECTED TO PROGRESS SLOWLY EWD/SEWD TONIGHT...BUT LARGELY REMAINING ALONG/NORTH OF THE FRONT...ENHANCED BY A STRONG NOCTURNAL LOW LEVEL JET OVER THE PLAINS/MO VALLEY. ...NERN CO INTO CENTRAL HIGH PLAINS... GUIDANCE INDICATES A SURFACE LOW WILL DEVELOP OVER SERN CO WITH A STRONG ENELY SURFACE PRESSURE GRADIENT DEVELOPING OVER ERN CO. RESULTANT UPSLOPE FLOW WILL ADVECT MOISTURE WWD TOWARD THE FOOTHILLS AND CONTRIBUTE TO DESTABILIZATION THIS AFTERNOON AS STRONG HEATING OCCURS EAST OF THE MOUNTAINS. WITH SURFACE DEW POINTS INCREASING INTO THE MID-UPPER 40S...MUCAPE IS EXPECTED TO REACH 500-1000 J/KG. LOW LEVEL UPSLOPE WINDS COUPLED WITH DIVERGENCE ALOFT ASSOCIATED WITH THE LEFT EXIT REGION OF THE STRONG UPPER JET WILL ENHANCE THUNDERSTORM POTENTIAL THIS AFTERNOON AND EVENING. STRONGLY VEERING WIND PROFILES WITH HEIGHT WILL ENHANCE ORGANIZATION AND INTENSITY OF CONVECTION WITH STRONG/SEVERE STORMS EXPECTED INCLUDING A FEW SUPERCELLS. LARGE HAIL...DAMAGING WIND GUSTS AND AN ISOLATED TORNADO OR TWO WILL BE POSSIBLE. ACTIVITY MAY GROW UPSCALE INTO AN EWD MOVING MCS THAT MOVES INTO PARTS OF THE CENTRAL PLAINS LATER TONIGHT. ...ERN CAROLINAS INTO SERN VA... WATER VAPOR IMAGERY INDICATES COLD UPPER LOW /-16C AT 500 MB/ IS LIFTING NEWD FROM SC TOWARD ERN NC AND IS EXPECTED TO ENHANCE THUNDERSTORM ACTIVITY AGAIN THIS AFTERNOON. VISIBLE IMAGERY SHOWS CLOUDS ARE CLEARING/THINNING OVER PARTS OF NC IN ADVANCE OF THE SYSTEM...WHICH IS ALLOWING STRONG HEATING/DESTABILIZATION TO OCCUR. ALTHOUGH WINDS ALOFT AND VERTICAL SHEAR WILL REMAIN MARGINALLY SUPPORTIVE FOR ORGANIZED CONVECTIVE STRUCTURES...VERY FAVORABLE THERMODYNAMIC ENVIRONMENT SUGGESTS POTENTIAL FOR SEVERE STORMS TO DEVELOP THIS AFTERNOON AND EVENING CAPABLE OF PRODUCING LARGE HAIL AND LOCALIZED DAMAGING WIND GUSTS. .....LOWER MS VALLEY... STRONG HEATING AMIDST A NEWD-ADVANCING WARM FRONT WILL SUPPORT ISOLATED TO WIDELY SCATTERED TSTMS. BOUNDARY-LAYER DEWPOINTS IN THE 60S NEAR AND SW OF THE FRONT WILL SUPPORT MODERATE TO STRONG DESTABILIZATION...WITH STEEP LOW-LEVEL LAPSE RATES LIKELY YIELDING DCAPE VALUES IN EXCESS OF 1000 J/KG. VERY WEAK FLOW THROUGHOUT THE TROPOSPHERE WILL SUPPORT A PULSE CONVECTIVE MODE...AND A LOW THREAT FOR DMGG WIND GUSTS AND PERHAPS MARGINALLY SVR HAIL CANNOT BE RULED OUT WITH THE STRONGEST STORMS. ..WEISS/GARNER.. 05/23/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1630.html
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