SPC 1200Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1257 AM CDT SAT JUN 02 2012 VALID 021200Z - 031200Z ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS ERN CO TO SRN HIGH PLAINS... ...SYNOPSIS... CONUS UPPER-AIR PATTERN THIS PERIOD WILL BE DOMINATED BY ERN TROUGHING AND RIDGING OVER ROCKY MOUNTAIN STATES. MIDDLE-UPPER LEVEL CYCLONE NOW OVER LOWER MI IS FCST TO DEEPEN EARLY IN PERIOD...THEN MOVE ERRATICALLY NEWD TO EWD ACROSS LH AND ADJOINING PORTIONS ONT. LOW-AMPLITUDE PERTURBATIONS ARE EVIDENT ON BACK SIDE OF ASSOCIATED CYCLONIC-FLOW FIELDS...OVER IL/INDIANA AND OVER ERN SD/SWRN MN/NWRN IA AREA. 500-MB VORTICITY FIELDS ACCOMPANYING EACH OF THESE PERTURBATIONS SHOULD MERGE/STRENGTHEN THROUGH PERIOD...WITH HEIGHT FALLS FROM MID-ATLC TO SRN APPALACHIANS THROUGH 3/06Z. LOW-AMPLITUDE MID-UPPER PERTURBATION NOW OVER GREAT BASIN REGION IS EXPECTED TO PENETRATE MEAN RIDGE POSITION OVER WRN/CENTRAL CO DURING EARLY-MID AFTERNOON...THEN MOVE SEWD AND AMPLIFY SOMEWHAT BY 00Z FROM NWRN TX PANHANDLE TO SERN WY. TROUGH THEN WILL MOVE EWD ACROSS KS THROUGH REMAINDER PERIOD. FARTHER NW...MOISTURE CHANNEL IMAGERY INDICATES SHORTWAVE TROUGH JUST OFFSHORE PAC NW...WHICH IS FCST TO CROSS ID PANHANDLE AROUND 2/18Z...THEN MOVE OVER SRN AB DURING LATE AFTERNOON. THIS WILL CAUSE HEIGHT FALLS ACROSS MUCH OF MT...AS WELL AS EWD MOVEMENT OF LOW-LEVEL COLD FRONT FROM NRN ROCKIES TO NRN HIGH PLAINS. LEE TROUGHING WILL INTENSIFY AHEAD OF THAT FRONT AND SEWD ALONG HIGH PLAINS TO WEAK FRONTAL-WAVE/LEE-SIDE LOW OVER BORDER AREA OF TX PANHANDLE AND NM. FRONTAL ZONE WILL EXTEND ESEWD ACROSS SRN PANHANDLE TO SRN OK OR N-CENTRAL TX...MORE SPECIFIC POSITION STRONGLY DEPENDENT ON STRENGTH/TIMING OF PLUME OF STATIC STABILITY TO ITS N...AS REINFORCED BY MORNING CONVECTION. THIS BOUNDARY SHOULD MOVE NNEWD ACROSS TX PANHANDLE AND OK THROUGH PERIOD AS WARM FRONT. LATE-AFTERNOON DRYLINE SHOULD EXTEND FROM TX BIG BEND REGION NNEWD TO FRONTAL INTERSECTION OVER NW TX. ...ERN CO TO SRN HIGH PLAINS... WIDELY SCATTERED TO SCATTERED TSTMS ARE EXPECTED TO DEVELOP DURING EARLY-MID AFTERNOON...AIDED BY STG HEATING OF HIGHER TERRAIN AND AT LEAST MODEST UPSLOPE COMPONENT OF LOW-LEVEL FLOW. DAMAGING GUSTS AND SPORADIC LARGE HAIL ARE POSSIBLE. CONVECTION MAY ALREADY BE WELL-FORMED UPON EXIT FROM MOUNTAINS...WITH ADDITIONAL GROWTH/PROPAGATION EWD ACROSS FOOTHILLS AND HIGH PLAINS OF CO AND NERN NM. VERY STEEP LOW-MIDDLE LEVEL LAPSE RATES WILL ACCOMPANY PERIOD OF STRONGEST PRECONVECTIVE/DIABATIC SFC HEATING. THIS WILL COMBINE WITH PLUME OF SFC DEWPOINTS 40S TO MID 50S F OVER PLAINS PORTION OF OUTLOOK AREA...TO YIELD MLCAPE RANGING FROM 1000-1500 J/KG OVER ERN CO TO 2000-2500 J/KG OVER PANHANDLES. WEAKNESS OF MID-UPPER LEVEL WINDS WILL LIMIT DEEP-LAYER SHEAR. HODOGRAPHS ARE PROGGED TO BE RATHER SMALL OVER MUCH OF THIS AREA...ALTHOUGH STG DIRECTIONAL SHEAR IS FCST. ...NW TX/SW OK...CONDITIONAL SVR RISK... FARTHER SE ALONG WARM FRONT...DEVELOPMENT IS MUCH MORE CONDITIONAL AND UNCERTAIN...DUE TO COMBINATION OF RELATIVELY WEAK BAROCLINIC LIFT AND INCREASING DISTANCE FROM MID-UPPER LEVEL PERTURBATION. FCST SOUNDINGS SUGGEST CAP MAY HOLD THROUGH LATE AFTERNOON AND PERHAPS ENTIRE AFTERNOON/EVENING PERIOD SE OF AFOREMENTIONED TSTM PLUME. ISOLATED DEVELOPMENT...HOWEVER...CANNOT BE RULED OUT. IF A SUSTAINED TSTM CAN DEVELOP IN REGIME OF STG HEATING ALONG FRONT...OVER NW TX/SW OK...STEEP LAPSE RATES AND FAVORABLE DEEP-LAYER SHEAR WILL SUPPORT POTENTIAL FOR LARGE/POTENTIALLY SIGNIFICANT HAIL. HOWEVER...THREAT APPEARS TOO TENUOUS AND ISOLATED ATTM TO DRAW MORE THAN 5% UNCONDITIONAL SVR PROBABILITY. ...NRN ROCKIES/WRN MT... WIDELY SCATTERED TSTMS SHOULD FORM OVER MOUNTAINS DURING EARLY-MID AFTERNOON...INVOF FRONTAL ZONE...WITH ADDITIONAL DEVELOPMENT POSSIBLE FARTHER E ACROSS CENTRAL/SRN MT LATE AFTERNOON INTO EARLY EVENING. MOVING OVER FAVORABLY MIXED BOUNDARY LAYER...SOME OF THIS ACTIVITY MAY PRODUCE GUSTS NEAR SVR LEVELS WITH RISK OF WIND DAMAGE. AS HEIGHTS FALL AND GRADIENT ALOFT TIGHTENS SE OF EJECTING NRN-ROCKIES WAVE...EFFECTIVE SHEAR MAGNITUDES SHOULD INCREASE TO 40-50 KT RANGE OVER MUCH OF THIS REGION...WITH MLCAPE AROUND 500 J/KG. POTENTIAL FOR BETTER-ORGANIZED OR HIGHER-MAGNITUDE SVR WILL BE LIMITED BY LACK OF GREATER LOW-LEVEL MOISTURE. ...MID MS VALLEY... PLUME OF RELATIVELY COLD AIR ALOFT WILL ACCOMPANY NW-FLOW PERTURBATION ACROSS THIS REGION AT TIME OF MAX DIURNAL WARMTH... JUXTAPOSED WITH ADEQUATE RESIDUAL MOISTURE IN BOUNDARY LAYER. NET RESULT SHOULD BE WEAKLY CAPPED AIR MASS SUPPORTING MLCAPE IN 250-700 J/KG RANGE...AMIDST 35-45 KT EFFECTIVE SHEAR MAGNITUDES. ISOLATED/MRGL SVR HAIL IS POSSIBLE...WITH POTENTIAL FOR LARGER HAIL AND/OR SVR WIND SUBSTANTIALLY CONSTRAINED BY LACK OF MORE ROBUST BUOYANCY. THREAT SHOULD SHIFT SEWD ACROSS SRN IL/WRN KY THEN DIMINISH QUICKLY AFTER DARK. ..EDWARDS/LEITMAN.. 06/02/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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