SPC 0600Z Day 2 Outlook
DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1246 AM CDT THU MAY 10 2012 VALID 111200Z - 121200Z ...NO SVR TSTM AREAS FORECAST... ...SYNOPSIS... PROGRESSIVE MID-UPPER LEVEL PATTERN FCST THROUGH PERIOD...FEATURING THREE PRIMARY TROUGHS... 1. ERN-CONUS SYNOPTIC TROUGH -- NOW EXTENDING FROM QUE/ONT BORDER SWD ACROSS SRN APPALACHIANS TO FL COASTAL BEND. SEVERAL SHORTWAVE TROUGHS OF VARYING AMPLITUDE WILL PIVOT CYCLONICALLY THROUGH THIS FEATURE...WITH NET EWD MOTION OF MAIN TROUGH TO NRN/WRN NEW ENGLAND AND COASTAL MID-ATLC REGION BY 11/12Z. THIS TROUGH WILL MOVE OFFSHORE NRN ATLC COAST AND OVER PORTIONS CANADIAN MARITIMES BY 1200Z. 2. NRN-STREAM SHORTWAVE TROUGH -- NOW MOVING INLAND PAC NW. FEATURE SHOULD MOVE ENEWD OBLIQUELY ACROSS CANADIAN BORDER REGION AND NRN ROCKIES DAY-1. BY START OF PERIOD...POSITIVELY TILTED TROUGH SHOULD EXTEND FROM WRN MB SWD ACROSS MT AND NWRN WY... SHIFTING EWD TO FAR NWRN ONT AND MN BY END OF PERIOD. 3. SRN-STREAM LOW -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER NWRN MEX -- FCST TO MOVE EWD ACROSS TX BIG-BEND AREA DAY-1...THEN PIVOT NEWD OVER PORTIONS NW/N-CENTRAL TX BY ABOUT 12/00Z. BY 12/12Z...REMNANTS OF THIS LOW SHOULD BE OVER NE TX...WITH BROADLY CYCLONIC FLOW FROM PERMIAN BASIN/LOWER PECOS VALLEY REGION ACROSS LOWER RIO GRANDE VALLEY TO LOWER MS DELTA. SYSTEM IS EXPECTED TO FILL GRADUALLY THROUGHOUT THIS PROCESS. PROGS ARE NOT AS DIVERGENT AS BEFORE WITH TRACK/TIMING OF THIS SYSTEM...BUT STILL OFFER IMPORTANT MESO-ALPHA SCALE DIFFERENCES PARTICULARLY FROM ABOUT MID-PERIOD ONWARD. AT SFC...COLD FRONT WAS ANALYZED AT 10/03Z FROM JUST OFFSHORE NC SWWD ACROSS NRN FL THEN WSWWD OVER NERN THROUGH W-CENTRAL GULF...BECOMING QUASISTATIONARY AND DIFFUSE INTO MTNS OF NERN MEX. SECONDARY BAROCLINIC ZONE WAS EVIDENT FROM MIDDLE TX COAT WSWWD ACROSS RIO GRANDE BETWEEN DRT-LRD. THESE BOUNDARIES SHOULD BLEND THEN LIFT NWD ACROSS MIDDLE-UPPER TX COAST AS WARM FRONT DAY-2...IN ADVANCE OF LOW SLOWLY EJECTING OUT OF MEX. INLAND PENETRATION OF THIS BOUNDARY IS UNCERTAIN...DEPENDING STRONGLY ON TRACK OF MID-UPPER WAVE AND ON REINFORCEMENT/REALIGNMENT BY ANTECEDENT CONVECTIVE PROCESSES. ...S-CENTRAL/SE TX... SCATTERED TO LOCALLY NUMEROUS TSTMS SHOULD OCCUR EPISODICALLY THROUGH PERIOD...WHERE RICH LOW-LEVEL THETAE KEEPS EFFECTIVE LIFTED PARCELS SFC-BASED. ISOLATED SVR GUSTS AND HAIL ARE POSSIBLE...AND THERE IS AT LEAST MRGL/CONDITIONAL TORNADO RISK. RICH LOW-LEVEL MOISTURE WAS ANALYZED INVOF FRONT AND WITHIN ABOUT 200 NM TO ITS N...WITH INLAND SFC DEW POINTS MID-UPPER 60S F AND 70S OFFSHORE. FAVORABLE MOISTURE IS EXPECTED TO REMAIN IN PRIMARY FRONTAL ZONE...THROUGH DAY-1 INTO THIS PERIOD. SVR POTENTIAL APPEARS GREATEST DURING AFTERNOON/EVENING HOURS WHEREVER THIS AIR MASS EXPERIENCES SUSTAINED/SFC DIABATIC HEATING...YIELDING 1500-2500 J/KG MLCAPE IN MODIFIED FCST SOUNDINGS. MIDDLE-UPPER TX COASTAL PLAIN SHOULD RESIDE BENEATH DIFLUENT LEFT-EXIT REGION OF SOMEWHAT CYCLONICALLY CURVED/SUBTROPICAL JET MAX S-SE OF UPPER LOW...AIDING LARGE SCALE ASCENT IN WAKE OF EARLIER CONVECTION. MOST FAVORABLE LOW-LEVEL SHEAR SHOULD OCCUR INVOF WARM FRONT...WHERE BACKED SFC WINDS WILL YIELD ENLARGED LOW-LEVEL HODOGRAPHS. MESOSCALE DEPENDENCY OF BOTH CONVECTIVE PROCESSES AND FRONTAL POSITION RENDER OUTLOOK TOO UNCERTAIN FOR CATEGORICAL AREA ATTM. ...WI-KS... WIDELY SCATTERED TO SCATTERED TSTMS ARE POSSIBLE INVOF SFC COLD FRONT...PRIMARILY DURING AFTERNOON INTO EARLY EVENING WHEN BOUNDARY-LAYER LAPSE RATES AND BUOYANCY WILL BE MAXIMIZED. MRGL MOISTURE WILL BE MAIN LIMITING FACTOR FOR CONVECTIVE LONGEVITY AND FOR SVR POTENTIAL...WITH NEAR-SFC TRAJECTORIES EMANATING FROM CONTINENTAL ANTICYCLONE THAT FOLLOWS NERN-CONUS TROUGH AND RELATED FROPA. STILL...RESIDUAL/EVAPOTRANSPIRATIVE CONTRIBUTIONS TO BOUNDARY-LAYER MOISTURE SHOULD RESULT IN NARROW PREFRONTAL PLUME OF 50S SFC DEW POINTS. VERY ISOLATED STG-SVR GUST CANNOT BE RULED OUT...SINCE THERE WILL BE SOME SFC-BASED TSTMS ACCESSING DIABATICALLY HEATED/MIXED PREFRONTAL BOUNDARY LAYER. HOWEVER...GIVEN VERY WEAK LOW-MIDDLE LEVEL BULK SHEAR FCST OVER FRONTAL CORRIDOR...ANY SUCH THREAT APPEARS TOO CONDITIONAL/SPARSE ATTM TO ASSIGN UNCONDITIONAL SVR PROBABILITIES. ..EDWARDS.. 05/10/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day2otlk_0600.html
Be First to Comment