DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0749 AM CDT SAT MAR 15 2014 VALID 151300Z - 161200Z ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL TX/ARKLATEX TO LOWER DELTA REGION AND MS COAST... ...SYNOPSIS... UPPER-AIR PATTERN WILL BE DOMINATED THIS PERIOD BY HIGH-AMPLITUDE BUT PROGRESSIVE RIDGING...MOVING EWD FROM W COAST...AND LARGE CYCLONIC GYRE COVERING MUCH OF ERN CANADA AND CENTERED OVER HUDSON BAY. E OF THAT RIDGE--TWO SHORTWAVE TROUGHS WILL SERVE AS PRIMARY MID-UPPER INFLUENCES ON CONVECTIVE POTENTIAL DAY-1... 1. SRN-STREAM PERTURBATION NOW EVIDENT IN MOISTURE-CHANNEL IMAGERY OVER ERN NM...FAR W TX AND CHIHUAHUA. THIS TROUGH WILL LOSE AMPLITUDE AS EMBEDDED 500-MB VORTICITY MAX/WEAK CIRCULATION EJECTS ENEWD ACROSS N-CENTRAL TX/EXTREME S-CENTRAL OK AROUND 00Z...REACHING SERN OK/SWRN AR/NE TX BY END OF PERIOD. 2. NRN-STREAM TROUGH CURRENTLY MOVING SEWD ACROSS PORTIONS SRN MT...WRN WY AND ERN UT. THIS FEATURE WILL TURN SSEWD ACROSS SRN ROCKIES AND INTENSIFY CONSIDERABLY BY 12Z...REACHING LOWER-MIDDLE PECOS VALLEY AND PORTIONS N-CENTRAL MEX. CYCLONIC FLOW ASSOCIATED WITH THESE FEATURES WILL BROADEN ACROSS SRN PLAINS AND NRN MEX...WITH HEIGHT FALLS INTENSIFYING AND SHIFTING SLOWLY EWD ACROSS THESE REGIONS AND NWRN GULF BY END OF PERIOD. AT SFC...11Z ANALYSIS SHOWED WAVY/QUASISTATIONARY FRONTAL ZONE FROM MO BOOTHEEL REGION WSWWD ACROSS ERN/SWRN OK...NW TX...BETWEEN LBB-MAF...AND OVER SERN NM. WARM FRONTOGENESIS WAS EVIDENT FROM BETWEEN DYS-CDS EWD ACROSS TXK AREA AND SRN AR. BOTH OF THESE BOUNDARIES ARE EXPECTED TO BECOME ILL-DEFINED TODAY AS RETURN FLOW OCCURS AHEAD OF SEPARATE COLD FRONT MOVING SEWD ACROSS CENTRAL HIGH PLAINS...AND PERHAPS MORE IMPORTANTLY...GROWING AREAS OF CLOUDS...PRECIP AND TSTMS OVER TX AND OK RECONFIGURE BOUNDARY-LAYER BAROCLINICITY CONSIDERABLY ON MESOSCALE. ...SRN PLAINS...MORNING THROUGH EVENING... MESSY SCENARIO EVIDENT WITH SCATTERED-NUMEROUS SHOWERS AND TSTMS EXPECTED TO DEVELOP THROUGH REMAINDER MORNING/EARLY-AFTN HOURS ACROSS PORTIONS W-CENTRAL/NW/N-CENTRAL TX AND MUCH OF OK...OFFERING MRGL WIND/HAIL RISK. ADDITIONAL TSTMS SHOULD FORM THROUGH AFTN OVER CENTRAL TX AND MOVE/SPREAD ENEWD....THESE HAVING BETTER-ORGANIZED SVR THREAT. THIS PROCESS WILL OCCUR AS LARGE-SCALE ASCENT ALOFT...IMMEDIATELY PRECEDING MID-UPPER TROUGH...BECOMES INCREASINGLY JUXTAPOSED WITH FAVORABLE LOW-LEVEL THETAE ADVECTION. MOISTURE TRANSPORT/ADVECTION ALREADY UNDERWAY ABOVE SFC WILL BE MANIFEST IN PRECONVECTIVE SFC ENVIRONMENT BY NWD SPREAD OF 60S F SFC DEW POINTS NOW IN CENTRAL/S TX TOWARD RED RIVER...AND 50S THAT HAVE REACHED SRN OK. THICK MIDDLE-HIGH CLOUDS WILL PRECLUDE STG SFC DIABATIC HEATING ACROSS MUCH OF THIS AREA...HOWEVER...COMBINATION OF DIFFUSE INSOLATION AND WAA WILL BOOST MLCAPE AND REDUCE MLCINH THROUGHOUT MIDDAY INTO AFTN IN PRECONVECTIVE AIR MASS. TSTM COVERAGE SHOULD EXTEND AND SHIFT EWD ACROSS NRN/CENTRAL TX THROUGH AFTN AND INTO EVE...AS INFLOW-LAYER AIR MASS MOISTENS. BUOYANCY WILL DEPEND STRONGLY ON AVAILABILITY OF LOCALIZED POCKETS OF ENHANCED/SUSTAINED INSOLATION OVER CENTRAL TX...AND ABSENCE OF PRECIP/OUTFLOW FARTHER N...NEAR AND N OF I-20. ALTHOUGH LOW-LEVEL WINDS WILL REMAIN WEAK THROUGH MUCH OF AFTN...LIMITING HODOGRAPH SIZE...WRN RIM OF LLJ WILL ENLARGE HODOGRAPHS AROUND 00Z AND THEREAFTER FOR ANY SFC-BASED TSTMS DEVELOPING AND MOVING EWD/ENEWD FROM CENTRAL TO E-CENTRAL/NE TX. THIS CORRIDOR REPRESENTS MOST PROBABLE JUXTAPOSITION OF FAVORABLE BUOYANCY/SHEAR FROM LATE AFTN INTO EVENING. FARTHER S INTO S TX...THOUGH CAPE WILL BE GREATER...SO WILL CINH...AND FOCI FOR CONVECTIVE-SCALE LIFT BECOME MORE UNCLEAR. ...SE TX TO MS DELTA/COAST REGIONS...TONIGHT... ATTM IT STILL IS UNCERTAIN WHETHER TX CONVECTIVE REGIME WILL 1. RUN CONTINUOUSLY INTO LA/MS. SOME SWD BACKBUILDING IS PSBL INTO SE TX AND SWRN LA...THOUGH DEAMPLIFICATION OF UPPER WAVE FARTHER N AND RELATED LACK OF LARGE-SCALE ASCENT EXTENDING SWD ACROSS SABINE RIVER AREA MAY DISFAVOR THAT IDEA. 2. AS MOST CONVECTION-PERMITTING HIGH-RES MODELS SUGGEST...DEVELOP AS SEPARATE AREA OF TSTMS AND BECOME SFC-BASED CLOSER TO GULF COAST OVER LA/MS. FCST SOUNDINGS SUGGEST ACCOMPANYING/WEAKLY CAPPED LOW-LEVEL WAA ZONE THAT WILL BE ACCOMPANIED BY LARGE...SUPERCELL-FAVORING LOW-LEVEL HODOGRAPHS AND STRENGTHENING DEEP SHEAR--E.G. EFFECTIVE SRH EXCEEDING 400 J/KG AND EFFECTIVE SHEAR MAGNITUDES 45-60 KT. THOUGH MID-60S DEW POINTS ARE FCST...LAPSE RATES WILL BE WEAKER THAN FARTHER W...KEEPING MLCAPE/MUCAPE AROUND 1000 J/KG OR LESS. WEAK LOW-LEVEL LAPSE RATES DURING OVERNIGHT HOURS MAY LIMIT VIGOR OF MANY UPDRAFTS...DESPITE TECHNICALLY SFC-BASED CHARACTER OF EFFECTIVE-INFLOW PARCELS IN FCST SOUNDINGS. ...NRN OK/EXTREME SRN KS... SOME MOIST ADVECTION ALSO MAY EXTEND OUT FROM BENEATH CLOUD SHIELD AND INTO BETTER-HEATED AREAS ACROSS PORTIONS NRN OK/SRN KS...AHEAD OF HIGH-PLAINS COLD FRONT. THIS COULD FOSTER CONDITIONAL/SHORT-LIVED POTENTIAL FOR A FEW STG-MRGL SVR TSTMS IN THAT AREA. MID-UPPER SUPPORT WILL DIMINISH WITH NWD EXTENT...LOW-LEVEL FLOW/SHEAR WILL BE WEAK...AND LOW-LEVEL LIFT IS IN QUESTION GIVEN LACK OF BOUNDARIES OTHER THAN DIFFERENTIAL-HEATING ZONES AND DECAYING/DIFFUSE FRONT. STILL...STEEP DEEP-LAYER LAPSE RATES...MLCAPE 1000-1500 J/KG...AND ENOUGH HEATING TO REMOVE CINH ARE ANTICIPATED...SUGGESTING ISOLATED GUSTS/HAIL NEAR SVR LIMITS MAY OCCUR. MRGL SVR PROBABILITIES ACCORDINGLY HAVE BEEN EXTENDED NWD INTO THIS REGION. ISOLATED TSTMS NEAR SVR LEVELS ALSO MAY FORM ALONG COLD FRONT AFTER DARK AS IT ENCOUNTERS RESIDUAL/MRGLLY FAVORABLE LOW-LEVEL MOISTURE/INSTABILITY. ..EDWARDS/MOSIER.. 03/15/2014
Posted on: Sat, 15 Mar 2014 15:17:51 +0000
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