SPC AC 202000

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0300 PM CDT WED APR 20 2016

   VALID 202000Z - 211200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FOR A LARGE PART OF CNTRL TX
   INTO THE TX PANHANDLE...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLIGHT RISK...

   ...THERE IS A MRGL RISK OF SVR TSTMS FOR A PORTION OF THE LOWER RIO
   GRANDE VALLEY...

   ...SUMMARY...
   ISOLATED TO SCATTERED SEVERE THUNDERSTORMS WILL BE POSSIBLE IN THE
   LATE AFTERNOON INTO TONIGHT...CENTERED ON NORTHWEST TEXAS. HAIL AND
   WIND SHOULD BE THE PRIMARY HAZARDS.

   MINOR CHANGES TO THE PREVIOUSLY ISSUED OUTLOOK ARE AS FOLLOWS:

   1) REMOVED LOW-WIND PROBABILITIES IN THE SABINE RIVER VALLEY AND
   PORTIONS OF LA.  A LOOSELY ORGANIZED SUB-SEVERE MCS CONTINUES TO
   PUSH EWD ACROSS SWRN LA DURING THE MID-AFTERNOON.  ALTHOUGH
   WATER-LOADED DOWNDRAFTS CAPABLE OF A LOCALIZED STRONG GUST CANNOT BE
   RULED OUT...WEAK CORES EMBEDDED IN THE LINE WILL LIKELY REMAIN
   SUB-SEVERE.

   2) REMOVED LOW HAIL/WIND PROBABILITIES OVER PARTS OF ORE/WA FOR
   ISOLD STORM ACTIVITY EXPECTED TO DEVELOP THIS EVENING.  TREND IN
   OPERATIONAL MODEL GUIDANCE SUGGESTS LOWER HAIL POTENTIAL AND RECENT
   RUNS OF THE HRRR IMPLY ONLY A GENERAL THUNDERSTORM RISK.

   3) ADDED A SMALL PART OF THE EDWARDS PLATEAU TO LOW HAIL/WIND
   PROBABILITIES.  PLEASE REFERENCE MCD NUMBER 424 FOR SHORT-TERM
   DETAILS.

   4) ADJUSTED THE NWRN EXTENSION OF SLIGHT RISK EQUIVALENT HAIL/WIND
   PROBABILITIES CLOSER TO THE CAPROCK IN THE TX PANHANDLE TO ACCOUNT
   FOR RECENT TRENDS IN STORM-SCALE GUIDANCE DEVELOPING STORMS LATER
   THIS AFTERNOON/EVENING.

   ..SMITH.. 04/20/2016

   .PREV DISCUSSION... /ISSUED 1124 AM CDT WED APR 20 2016/

   ...PORTIONS OF THE SRN PLAINS...

   AN OUTFLOW BOUNDARY -- RELATED TO A DECAYING NOCTURNAL MCS -- ARCHES
   FROM THE LOWER SABINE VALLEY TO THE MIDDLE TX COASTAL PLAIN TO THE
   EDWARDS PLATEAU OF TX LATE THIS MORNING. THIS BOUNDARY CONTINUES
   SPREADING SWD/SEWD WHILE CONVECTIVE PROCESSING OCCURS OVER SERN TX.
   BEHIND THIS BOUNDARY...RECYCLED MOISTURE IS EVIDENT NWD ACROSS THE
   SRN PLAINS AMIDST MESOSCALE RIDGING...WITH DEWPOINTS IN THE UPPER
   40S TO THE 50S. MEANWHILE...WATER VAPOR LOOPS IMPLY A MID-LEVEL
   SPEED MAX AND ACCOMPANYING VORTICITY BANNER ORBITING AROUND THE SRN
   RIM OF BROADLY CYCLONIC FLOW...WITH THESE FEATURES PRESENTLY
   CROSSING PARTS OF THE CNTRL/SRN ROCKIES AND VICINITY. IN
   RESPONSE...LEE SFC TROUGHING WILL FACILITATE AN INFLUX OF MODESTLY
   RICHER LOW-LEVEL MOISTURE INTO PARTS OF W TX WHILE AN EML PLUME
   OVERSPREADS THE RETURNING MOISTURE.

   MORE ROBUST TSTM DEVELOPMENT ACROSS PARTS OF THE SERN TX PANHANDLE
   AND ERN TX S PLAINS WILL LIKELY BE DELAYED UNTIL LATE AFTERNOON/THIS
   EVENING...OWING TO THE ONLY GRADUAL INFLUX OF RICHER LOW-LEVEL
   MOISTURE AND EVENTUAL SWD PROGRESSION OF A REINFORCING SYNOPTIC
   BOUNDARY LATE IN THE PERIOD. THE PRESENCE OF 35-50 KT OF EFFECTIVE
   BULK SHEAR WILL BE SUFFICIENT FOR CONVECTIVE CLUSTERS WITH EMBEDDED
   SUPERCELLS TO SPREAD EWD/SEWD THROUGH THE EVENING AND OVERNIGHT
   HOURS...AS ELEVATED INFLOW CHARACTERIZED BY 1000-1500 J/KG OF MUCAPE
   FOSTERS INTENSE UPDRAFTS. ISOLATED TO SCATTERED SVR HAIL/WIND MAY
   ACCOMPANY THIS ACTIVITY AS IT MOVES ACROSS PARTS OF NWRN TX AND
   VICINITY...AFFECTING PORTIONS OF THE LOW ROLLING PLAINS AND TX BIG
   COUNTRY THROUGH THE OVERNIGHT HOURS.

   DIURNAL TSTM DEVELOPMENT WILL ALSO BE POSSIBLE OVER PORTIONS OF THE
   EDWARDS PLATEAU/CONCHO VALLEY THIS AFTERNOON INVOF THE
   AFOREMENTIONED OUTFLOW BOUNDARY. RECENT VIS SATELLITE TRENDS SUGGEST
   LESS SWD SURGE OF THIS SEGMENT OF THE BOUNDARY. AS THIS BOUNDARY
   STALLS AND BECOMES DIFFUSE...ISOLATED STRONG TO SVR TSTM DEVELOPMENT
   WITH WIND/HAIL COULD OCCUR AS MLCINH GRADUALLY ERODES IN ASSOCIATION
   WITH DIURNAL HEATING. HOWEVER...ANTECEDENT CAPPING WITH WEAK
   LARGE-SCALE ASCENT SHOULD LIMIT SVR COVERAGE IN THIS REGIME THROUGH
   THE AFTERNOON.

   ...PORTIONS OF THE LOWER SABINE VALLEY TO THE LOWER MS VALLEY...

   THE REMNANTS OF THE AFOREMENTIONED NOCTURNAL MCS WILL CONTINUE TO
   SPREAD EWD. OTHER CONVECTIVE DEVELOPMENT FARTHER E WILL CONTINUE IN
   A WEAKLY CAPPED...MOIST-SLY-FLOW REGIME. SOME INTENSIFICATION OF
   THIS ACTIVITY MAY OCCUR...AS INSOLATION/DIABATIC SFC-LAYER HEATING
   ENCOURAGE MODEST DIURNAL DESTABILIZATION. PRECIPITATION LOADING
   COULD SUPPORT A FEW WET MICROBURSTS CAPABLE OF LOCALLY DMGG WIND
   GUSTS. HOWEVER...POOR LAPSE RATES COMBINED WITH WEAK DEEP SHEAR WILL
   TEND TO MITIGATE SVR POTENTIAL...AS CONVECTION REMAINS LOOSELY
   ORGANIZED.

   ...CASCADES OF ORE/SW WA...

   MID-LEVEL HEIGHT FALLS/DCVA PRECEDING A MID-LEVEL VORT MAX
   APPROACHING THE COAST OF NRN CA/SRN ORE WILL ENCOURAGE TSTM
   DEVELOPMENT AS OROGRAPHIC CIRCULATIONS DIURNALLY STRENGTHEN THIS
   AFTERNOON. SUFFICIENT DEEP SHEAR WILL EXIST FOR ISOLATED SVR
   WIND/HAIL AS CONVECTION SPREADS NWD/NNEWD THROUGH THE EVENING.

   ...NRN/CNTRL/ERN IA...

   AN ARC OF LOW-TOPPED CONVECTION...WITH ISOLATED LIGHTNING...WILL
   LIKELY EVOLVE AMIDST MODEST LOW-LEVEL MOISTURE NEAR A FRONTAL
   OCCLUSION -- E OF A PRIMARY SFC CYCLONE MOVING NWD OVER WRN/CNTRL
   IA. AMBIENT VERTICAL VORTICITY NEAR THE SFC BOUNDARIES AND CYCLONE
   COUPLED WITH SUFFICIENT BUOYANCY/VORTICITY STRETCHING...MAY SUPPORT
   A FEW WEAK/TRANSIENT STORM-SCALE CIRCULATIONS WITH GUSTY WINDS/SMALL
   HAIL BEING THE PRIMARY CONCERNS -- AROUND PEAK DIURNAL HEATING.
   HOWEVER...ANTICIPATED POOR LAPSE RATES AND ONLY MODEST CYCLONE
   STRENGTH SUGGEST ANY SVR-TSTM/TORNADO POTENTIAL SHOULD BE TOO
   LIMITED FOR SVR PROBABILITIES.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z