SPC 2000Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0150 PM CST WED FEB 06 2013 VALID 062000Z - 071200Z ...NO SVR TSTM AREAS FORECAST... ...S AND SE TX AND SRN LA... SHORTWAVE UPPER TROUGH NOW MOVING THROUGH S TX WILL CONTINUE TO MOVE PARALLEL TO THE GULF COAST THROUGH LATE TONIGHT. DRY MIDLEVEL AIR /EVIDENT ON WATER VAPOR IMAGERY/ IN THE WAKE OF THE SHORTWAVE HAS OVERSPREAD S TX...COINCIDING WITH A DECREASE IN CONVECTIVE COVERAGE NEAR AND IMMEDIATELY E OF THE LOWER RIO GRANDE VALLEY. ADDITIONAL TSTMS MAY FORM OVER THE SERRANIA DEL BURRO MTNS OF NRN MX WITHIN A LOW-LEVEL UPSLOPE REGIME AND MOVE EWD TOWARDS DEEP S TX LATER THIS EVENING...BUT ANY ACCOMPANYING THREAT FOR HAIL WOULD APPEAR TO BE VERY ISOLATED/MARGINAL. MEANWHILE...A CLUSTER OF TSTMS ALONG COASTAL S TX IS SLOWLY SHIFTING OFFSHORE...WITH REDEVELOPMENT OF ISOLATED TSTMS OCCURRING NEAR A W-E ORIENTED OUTFLOW BOUNDARY. THESE STORMS COULD POSE A LOCALIZED RISK FOR HAIL/WIND AND PERHAPS A BRIEF/WEAK TORNADO. SEE MCD 116 FOR MORE DETAILS ON THE S TX PORTION OF THE HIGHLIGHTED AREA. LATER TONIGHT...STRENGTHENING WAA AHEAD OF THE SHORTWAVE UPPER TROUGH MAY SUPPORT THE DEVELOPMENT OF A WEAK SFC CYCLONE NEAR COASTAL SE TX INTO SRN LA. ALTHOUGH BUOYANCY WILL BE QUITE LIMITED...AND THERE IS UNCERTAINTY WHETHER SFC-BASED PARCELS CAN BE SUSTAINED...A NON-ZERO/CONDITIONAL RISK OF A DMGG WIND GUSTS/ISOLATED TORNADO MAY EXIST OVERNIGHT...WITH LOW-END PROBABILITIES MAINTAINED. ..ROGERS/DIAL.. 02/06/2013 .PREV DISCUSSION... /ISSUED 1028 AM CST WED FEB 06 2013/ ...S TX AND SRN LA REST OF TODAY THROUGH LATE TONIGHT... LOW-AMPLITUDE SHORTWAVE TROUGHS CROSSING NRN MEXICO AND S TX PER WATER VAPOR IMAGERY WILL CONTINUE TO SUPPORT EPISODIC CONVECTION THROUGH THE REMAINDER OF THE PERIOD. ONE AREA OF SCATTERED THUNDERSTORMS IS CURRENTLY MOVING OFF THE LOWER TX COAST. A MARGINAL SVR THREAT MAY LINGER IN THE SHORT-TERM FROM AROUND CRP TOWARD PSX GIVEN AROUND 50 KT OF DEEP SHEAR AND MODEST LOW-LEVEL DIRECTIONAL SHEAR PER CRP VWP DATA...ALONG WITH AROUND 1000 J/KG OF MLCAPE PER THE 12Z CRP RAOB. AS THE SHORTWAVE TROUGH ASSOCIATED WITH THIS ACTIVITY CONTINUES TO ADVANCE EWD OVER THE NWRN/N-CNTRL GULF...A STRENGTHENING SLY LOW-LEVEL JET WILL SHIFT EWD FROM THE UPPER TX COAST TO COASTAL LA. IN RESPONSE...CONVECTIVE COVERAGE WILL PROBABLY INCREASE OVER THE GULF WATERS...WITH WAA ATOP A CONVECTIVELY REINFORCED COASTAL BAROCLINIC ZONE SUPPORTING WIDESPREAD PRECIPITATION INLAND -- MAINLY STRATIFORM IN NATURE. ACCOMPANYING THETA-E DEFICITS SHOULD PRECLUDE ANY APPRECIABLE INLAND PENETRATION OF WARMER/MORE MOIST/UNSTABLE MARINE TRAJECTORIES WITHIN THE SFC LAYER...LIMITING BOUNDARY-LAYER DESTABILIZATION AND LIMITING AN INLAND SVR THREAT. HOWEVER...LATE TONIGHT...A WEAK SFC WAVE MAY DEVELOP ALONG THE BAROCLINIC ZONE AS WAA STRENGTHENS. DEPENDING ON THE LOCATION AND STRENGTH OF THE WAVE -- FOR WHICH UNCERTAINTY EXTENDS FROM ANTECEDENT CONVECTIVE TRENDS -- VERY MODEST BOUNDARY-LAYER DESTABILIZATION COULD OCCUR OVER COASTAL SECTIONS OF S-CNTRL AND SERN LA. A CONDITIONAL THREAT FOR A SVR WIND GUST AND POSSIBLY A BRIEF TORNADO CANNOT BE RULED OUT...GIVEN STRONG LOW-LEVEL AND DEEP SHEAR. REGARDLESS...THE LACK OF CONFIDENCE IN THE DEVELOPMENT OF SFC-BASED EFFECTIVE INFLOW LAYERS OVER INLAND LOCATIONS PRECLUDES THE INTRODUCTION OF HIGHER SVR PROBABILITIES. ADDITIONALLY...A FEW STORMS COULD IMPACT PARTS OF S TX THIS AFTERNOON AND EVENING IN THE WAKE OF MORNING CONVECTION...AS AN UPSLOPE REGIME AFFECTS THE ERN SLOPES OF THE NRN MEXICO MOUNTAINS AMIDST WEAK MID-LEVEL DCVA. AN ISOLATED SVR STORM CANNOT BE RULED OUT WITH THIS ACTIVITY GIVEN STRONG DEEP SHEAR AND STEEP MID-LEVEL LAPSE RATES PER FORECAST SOUNDINGS. HOWEVER...THE INFLUX OF DRIER AIR IN THE MID-LEVELS ACROSS NRN MEXICO FROM THE E PACIFIC PER RECENT WATER VAPOR IMAGES AND THE LACK OF STRONGER FORCING FOR ASCENT MAY PROVE HOSTILE FOR UPDRAFT DEVELOPMENT/MAINTENANCE. ...NWRN/N-CNTRL TX AND WRN OK THIS AFTERNOON AND EVENING... AN ISOLATED STORM OR TWO COULD DEVELOP ALONG A N/S-ORIENTED DRYLINE THIS AFTERNOON AND PERSIST INTO THE EVENING. ISOLATED OCCURRENCES OF GUSTY WINDS OR SMALL HAIL CANNOT BE RULED OUT. HOWEVER...FAIRLY HIGH LFC HEIGHTS...LIMITED DEEP MOISTURE...AND THE LACK OF STRONGER MID-LEVEL FORCING FOR ASCENT SHOULD GREATLY MITIGATE STORM STRENGTH/PERSISTENCE/COVERAGE. ...CNTRL/ERN KS AND NRN OK LATE TONIGHT... SCATTERED THUNDERSTORMS WILL LIKELY DEVELOP ALONG/JUST BEHIND A COLD FRONT ADVANCING SEWD INTO MARGINAL ELEVATED INSTABILITY. SMALL HAIL OR PERHAPS GUSTY WINDS CANNOT BE RULED OUT. HOWEVER...DOWNDRAFT PENETRATION TO THE SFC WILL LIKELY BE MITIGATED BY STRENGTHENING BOUNDARY-LAYER CINH OWING TO NOCTURNAL STABILIZATION AND THE UNDERCUTTING NATURE OF THE FRONT. THE LIMITED AMOUNT OF ELEVATED INSTABILITY SHOULD PRECLUDE ANY SVR-HAIL THREAT.
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_2000.html
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