SPC 0100Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0757 PM CDT THU APR 26 2012 VALID 270100Z - 271200Z ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL/SRN HIGH PLAINS... ...SYNOPSIS... OVER ERN CONUS...BROADLY CYCLONIC FLOW WITH WEAK/EMBEDDED SHORTWAVES IS EVIDENT FROM UPPER GREAT LAKES AND UPPER MS VALLEY ACROSS APPALACHIANS TO E COAST. MID-UPPER RIDGE OVER CENTRAL CONUS IS FCST TO CONTINUE MOVING EWD AND WEAKEN. THIS WILL OCCUR IN ADVANCE OF TWO PRIMARY AND NEARLY CONNECTED PHASES OF PROGRESSIVE...NEGATIVELY TILTED WRN TROUGHING... 1. HIGH-AMPLITUDE SHORTWAVE TROUGH...NEARLY SYNOPTIC IN SPATIAL SCALE...EVIDENT IN MOISTURE CHANNEL IMAGERY FROM OFFSHORE VANCOUVER ISLAND SEWD OVER ORE AND NWRN NV. THIS FEATURE WILL MOVE ENEWD TO SRN BC...SERN ID AND NERN UT BY END OF PERIOD. 2. COMPACT BUT STG SHORTWAVE PERTURBATION NOW MOVING NEWD FROM ERN AZ OVER 4-CORNERS REGION. AS HEIGHTS FALL AHEAD OF LARGER NWRN SYSTEM...THIS FEATURE WILL MAINTAIN NEGATIVE TILT AND MOVE NEWD TO CO/KS BORDER AREA BY 12Z. AT SFC...23Z ANALYSIS SHOWED CYCLONE OVER ST LAWRENCE RIVER JUST N OF NERN NY...OCCLUDED FRONT SWWD TO WRN VA/NERN WV TRIPLE POINT...WARM FRONT FROM THERE SEWD ACROSS NC. COLD FRONT EXTENDED SWWD FROM TRIPLE POINT OVER SERN KY AND NERN AR...BECOMING QUASISTATIONARY FROM CENTRAL AR WSWWD OVER NW TX. COLD FRONT SHOULD MOVE SWD TO NRN PORTIONS SC/GA/AL/MS OVERNIGHT AND DECELERATE. WRN SEGMENT WILL MOVE NEWD AS WARM FRONT OVER SRN/CENTRAL/WRN OK...BUT MAY BE DIFFUSED AT SFC BY TSTM OUTFLOW FARTHER W AND NW OVER PANHANDLES AND SWRN KS. SFC CYCLONE WILL CONSOLIDATE OVER ERN CO AND DEEPEN AS MID-UPPER SHORTWAVE TROUGH APCHS OVERNIGHT. ...CENTRAL/SRN HIGH PLAINS... COLD POOLS...LEFT-MOVERS AND MESSY STORM MODES CHARACTERIZE NRN PORTION OF BKN CONVECTIVE BAND FROM SERN CO/SWRN KS SSEWD ACROSS PANHANDLES...WITH LARGE HAIL AND SVR GUSTS STILL PSBL. ACTIVITY WILL BE MOVING EWD TOWARD AREA OF 40S SFC DEW POINTS OVER SWRN KS...BUT ALSO INCREASING MOISTURE ABOVE SFC AS LLJ STRENGTHENS. MEANWHILE...CONVECTION NEAR SRN END OF COMPLEX...OVER CENTRAL-ERN TX PANHANDLE...WILL MAINTAIN ACCESS TO GREATER LOW-LEVEL MOISTURE AND RELATIVELY UNIMPEDED...HIGHER-THETAE INFLOW N OF FRONT. REF WW 192 AND RELATED MESOSCALE DISCUSSIONS FOR NEAR-TERM FCST POTENTIAL FROM ERN CO/WRN KS SWD ACROSS TX/OK PANHANDLES. OVERALL COVERAGE MAY INCREASE OVERNIGHT AS STG DEEP-LAYER ASCENT APCHS AHEAD OF MID-UPPER TROUGH...MAINTAINING TSTMS AND SOME SVR THREAT ALL NIGHT OVER PORTIONS KS. ADDITIONAL/OVERNIGHT DEVELOPMENT WITH MAIN THREAT OF DAMAGING WIND MAY OCCUR OVER RELATIVELY UNDISTURBED AIR IN SERN CO...NW OF PANHANDLE COLD POOL..IN ENVIRONMENT OF STRENGTHENING DEEP-LAYER FLOW AND SHEAR. ...SRN APPALACHIANS REGION TO MID SOUTH... SERN CONUS SVR THREAT IS PAST ITS PEAK...AND IS FCST TO CONTINUE DIMINISHING THROUGH REMAINDER PERIOD DUE TO COMBINATION OF 1. EXPANDING COVERAGE OF OUTFLOW AIR... 2. DIABATIC SFC COOLING THAT WILL REDUCE MLCAPE AND STRENGTHEN MLCINH...AND 3. BOUNDARY-LAYER CAA WHERE FROPA OCCURS. STILL...BKN BANDS OF TSTMS WILL PERSIST FOR A FEW MORE HOURS PRECEDING COLD FRONT...STRONGEST CONVECTION BEING IN MOST BUOYANT AIR MASS OVER TN VALLEY REGION. ENVIRONMENT WILL CONTINUE TO BE CHARACTERIZED BY FAVORABLE DEEP-LAYER SHEAR FOR ORGANIZED MULTICELLS AND TRANSIENT SUPERCELL MODES. FARTHER W...CONVECTIVE COVERAGE AND ANY SVR HAIL/GUST THREAT THEREWITH WILL REMAIN MORE ISOLATED DUE TO BOTH WEAKER NEAR-FRONTAL CONVERGENCE AND NEAR-SFC COOLING. ...CENTRAL/WRN MT... BAND OF CONVECTION MOVING NEWD ACROSS PORTIONS W-CENTRAL/NWRN MT WITH SLGT SEWD BACKBUILDING POSSIBLE. ACTIVITY POSES RISK OF ISOLATED DAMAGING GUSTS FOR A FEW MORE HOURS...BEFORE MOVING INTO PROGRESSIVELY DRIER/LOWER-THETAE AIR MASS. THOUGH CAPPED...TFX SOUNDING SHOWED MRGL MLCAPE 100-200 J/KG AND ABOUT 50 KT EFFECTIVE SHEAR MAGNITUDE AVAILABLE TO PARCELS THAT CAN BE LIFTED FORCIBLY TO LFC ALONG OUTFLOW. RELATIVELY LOW-RH/INVERTED-V PROFILE ABOVE SKIN LAYER MAY SUPPORT GUST ENHANCEMENT. ..EDWARDS.. 04/27/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_0100.html
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