SPC 0600Z Day 2 Outlook
DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1256 AM CDT FRI MAY 04 2012 VALID 051200Z - 061200Z ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL PLAINS...IA...ADJOINING MO VALLEY REGION... ...SYNOPSIS... PATTERN WILL BE CHARACTERIZED GENERALLY BY MEAN RIDGING OVER MS VALLEY...AND TROUGHING OVER INTERIOR PAC COAST STATES/WRN GREAT BASIN REGION. WITHIN THAT...SERIES OF SHORTWAVES OF VARYING MAGNITUDE WILL TRANSLATE...MOST SUBSTANTIAL BEING EVIDENT IN MOISTURE CHANNEL IMAGERY ATTM OFFSHORE PAC NW. THIS PERTURBATION IS EXPECTED TO MOVE EWD ACROSS INTERIOR NWRN CONUS DAY-1...REACHING NRN ROCKIES AND NRN NV BY 5/12Z. TROUGH THEN SHOULD DEAMPLIFY BUT NOT NECESSARILY WEAKEN...AS IT CONTRACTS INTO SMALL CLOSED CYCLONE OVER SERN SK/SWRN MB BY 6/12Z. LATTER SOLUTION IS EVIDENT IN OPERATIONAL NAM AND ABOUT HALF OF SREF MEMBERS...BUT NOT ENOUGH TO AVOID SMOOTHING CLOSED LOW OUT OF SREF MEAN. MOST PROGS SHOW EARLIER/FARTHER W DEVELOPMENT OF AT LEAST TEMPORARILY CLOSED/CUTOFF LOW LATE IN PERIOD OVER CA. MEANWHILE...WEAKER/SRN-STREAM PERTURBATIONS NOW OVER NM SHOULD MOVE ANTICYCLONICALLY ACROSS CENTRAL/SRN PLAINS DAY-1...THEN SEWD ACROSS SRN APPALACHIANS REGION DAY-2. AT SFC...WAVY AND MOSTLY QUASISTATIONARY FRONTAL ZONE WAS ANALYZED AT 4/03Z FROM NERN NC NWD TO SFC LOW OVER ERN LK ONTARIO...WSWWD ACROSS SRN LOWER MI TO WAVE LOW OVER NEB/IA BORDER AREA...THEN SWWD ACROSS NWRN KS TO ANOTHER WEAK LOW OVER ERN CO. APCH OF NWRN CONUS SHORTWAVE TROUGH WILL SUPPORT GRADUAL DEEPENING/CONSOLIDATION OF CENTRAL-PLAINS FRONTAL-WAVE LOW OVER KS...DRIFTING NWD OVER CENTRAL NEB THROUGH 6/00Z...THEN MOVING EWD ACROSS SERN NEB/SRN IA THROUGH REMAINDER OF PERIOD. STRENGTHENING COLD FRONT...EXTENDING SWWD FROM CENTRAL-PLAINS LOW...SHOULD MOVE SEWD OVER CENTRAL HIGH PLAINS TO CENTRAL KS...NWRN OK...AND TX PANHANDLE BY END OF PERIOD. ERN CONUS FRONTAL ZONE SHOULD MOVE SWD ACROSS TIDEWATER AND MOUNTAINOUS NC/VA REGIONS AS COLD FRONT...WHILE BECOMING NEARLY STATIONARY OVER LOWER OH VALLEY AND SRN IA. WAVY DRYLINE SHOULD ASSUME LATE-AFTERNOON POSITION FROM CENTRAL-PLAINS LOW SWD ACROSS CENTRAL/WRN OK THEN SSWWD OVER W-CENTRAL SW TX. DESPITE ONLY MINOR DIFFERENCES IN UPPER-AIR PATTERN...SOME WAVE-PHASE RELATED UNCERTAINTIES REMAIN IN THIS FCST. OPERATIONAL SPECTRAL AND OLDER ECMWF RUN EACH IS A STG SLOW/WRN OUTLIER ON SFC LOW THIS PERIOD...COMPARED TO NAM AND MOST SREF MEMBERS. WHILE WEIGHTING FORECAST TOWARD SREF CONSENSUS...SMALLER-PROBABILITY FAILURE OF THAT CA CLOSED LOW TO DEVELOP WOULD MEAN EWD SHIFT OF RELATED VORTICITY FIELD...AND MORE WLY POSITION OF SFC LOW. ...CENTRAL PLAINS...IA...ADJOINING MO VALLEY REGION... AREA OF DEEP MOISTURE SHOULD POOL NE OF SFC LOW DURING AFTERNOON. ALTHOUGH EML-RELATED CINH WILL SUPPRESS DEVELOPMENT THROUGH MUCH OF AFTERNOON...COMBINATION OF RICH LOW-LEVEL THETAE IN CORRIDOR E-NE OF SFC LOW AND NEAR WARM FRONT WILL SUPPORT STG TO EXTREME BUOYANCY...WITH MLCAPE REACHING NEAR 5000 J/KG IN SOME LOCALES. OVERLAID ON SOME OF THIS BUOYANCY WILL BE STG VEERING OF WINDS WITH HEIGHT...CONTRIBUTING TO ENHANCED SRH INVOF LOW AND QUASISTATIONARY FRONT. ANY TSTMS THAT CAN DEVELOP IN THIS ENVIRONMENT WILL DO SO EXPLOSIVELY...WITH RAPID GROWTH TO SVR/SUPERCELLULAR LEVELS. ADDITIONAL CONVECTION SHOULD FORM DURING EVENING...WITH UPSCALE GROWTH INTO MCS POSSIBLE. EARLY STAGES OF LATE AFTERNOON/EARLY EVENING CONVECTION WILL OFFER RISK OF VERY LARGE/DAMAGING HAIL...TORNADOES AND SVR DOWNDRAFTS. THREAT MAY TRANSITION MORE DOMINANTLY TO DAMAGING WIND WITH TIME AS COLD POOL DEVELOPS. RELATIVE MIN IN TSTM/SVR POTENTIAL IS EXPECTED ALONG DRYLINE BETWEEN CENTRAL-PLAINS LOW AND THIS AREA...WHERE PROBABILITY IS VERY LOW THAT DIABATIC SFC HEATING AND DRYLINE CONVERGENCE WILL OVERCOME CINH AND BREACH EML. ...SW TX TO RED RIVER...AFTERNOON... VERY STG SFC INSOLATION OVER THIS CORRIDOR...IN TANDEM WITH DRYLINE-RELATED LIFT...MAY BE SUFFICIENT TO BREAK CAP IN AT LEAST ONE OR TWO LOCALES IN THIS CORRIDOR. ISOLATED TO WIDELY SCATTERED TSTMS MAY DEVELOP IN MID-LATE AFTERNOON...HIGH-BASED WITH ISOLATED DAMAGING GUSTS POSSIBLE. DEEP-LAYER SHEAR IS FCST TO BE WEAK...SUGGESTING SUPERCELL STRUCTURES...IF ANY...WOULD BE WEAK/TRANSIENT...SO HAIL THREAT SHOULD BE MRGL. HOWEVER...BUOYANCY MAY BECOME EXTREME...MLCAPE EXCEEDING 4000 J/KG WITHIN 50-75 NM E OF DRYLINE. TSTMS WILL DECLINE MARKEDLY IN COVERAGE/INTENSITY AFTER DARK. ...SERN CONUS... WIDELY SCATTERED TO SCATTERED TSTMS SHOULD DEVELOP DURING AFTERNOON...AGGREGATING INTO SEVERAL MULTICELLULAR CLUSTERS OVER SOME PARTS OF THIS REGION FROM CAROLINAS/GA TO TN VALLEY AND LOWER OH VALLEY. STG DIABATIC SFC HEATING WITH DEW POINTS 60S F WILL WEAKEN MLCINH RAPIDLY...WITH DEVELOPMENT MOST CONCENTRATED INVOF FRONT AND OUTFLOW BOUNDARIES. SOMEWHAT STEEP MIDLEVEL LAPSE RATES OF AROUND 8 DEG C/KM WILL SUPPORT MLCAPE 2000-3000 J/KG IN SOME LOCALES...SUPPORTING STG-SVR DOWNDRAFTS AND SPORADIC LARGE HAIL. WEAK DEEP-LAYER FLOW AND LACK OF APPRECIABLE DEEP SHEAR SUGGEST PREDOMINANT MULTICELLULAR AND PULSE MODES. MORE SPECIFIC/MESOSCALE FOCI INVOF FRONT...AND EFFECTIVE FRONTAL POSITION MODULATED BY PRIOR TSTM OUTFLOWS...ARE YET TO BE DETERMINED. AS SUCH...SPECIFIC FCST AREA OF MORE CONCENTRATED SVR THREAT IS NOT YET WARRANTED. ..EDWARDS.. 05/04/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day2otlk_0600.html
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