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Mesoscale Discussion 421
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   MESOSCALE DISCUSSION 0421
   NWS STORM PREDICTION CENTER NORMAN OK
   0845 PM CDT TUE APR 19 2016

   AREAS AFFECTED...A LARGE PART OF TEXAS

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 200145Z - 200415Z

   PROBABILITY OF WATCH ISSUANCE...20 PERCENT

   SUMMARY...TSTM CLUSTERS EVOLVING ACROSS PORTIONS OF WRN/NRN TX AT
   MID EVENING ARE FORECAST TO SPREAD ACROSS A LARGE PART OF TX THROUGH
   THE LATE EVENING AND INTO THE EARLY OVERNIGHT. THIS ACTIVITY WILL
   OFFER AN ISOLATED SVR WIND/HAIL RISK. WHILE CONVECTIVE TRENDS WILL
   CONTINUE TO BE MONITORED...WW ISSUANCE IS PRESENTLY UNLIKELY.

   DISCUSSION...MOISTURE-CHANNEL IMAGERY SUGGESTS THAT ANY SUBSTANTIVE
   MID-LEVEL ASCENT IS ONLY GLANCING CONDITIONALLY UNSTABLE AIR SAMPLED
   ACROSS PORTIONS OF CNTRL/WRN TX. SFC ANALYSIS AT 01Z PLACES A FRONT
   ARCHING FROM NEAR WICHITA FALLS TO S OF LUBBOCK AND THEN INTO
   E-CNTRL NM E OF CLOVIS. THAT PORTION OF THE BOUNDARY ACROSS WRN N TX
   TO THE TX S PLAINS IS BEING ENHANCED BY ONGOING COLD-POOL
   AMALGAMATION ASSOCIATED WITH A QUASI-LINEAR CONVECTIVE CLUSTER. A
   DRYLINE INTERSECTS THE BOUNDARY AT A TRIPLE POINT ANALYZED SSW OF
   LUBBOCK AND EXTENDS TO THE SWRN TX BIG BEND. THE DRYLINE IS
   RETREATING WWD FOLLOWING INITIAL NOCTURNAL DECOUPLING OF THE
   BOUNDARY LAYER. WHILE THE AFOREMENTIONED CONVECTIVE CLUSTER
   CONTINUES BACKBUILDING TOWARD THE TRIPLE POINT...MORE ISOLATED
   CONVECTION IS OCCURRING IN PROXIMITY TO THE DRYLINE SWD FROM THE
   PERMIAN BASIN TO THE STOCKTON PLATEAU. MEANWHILE...A PERSISTENT
   SUPERCELL CLUSTER IS NEARING THE RIO GRANDE RIVER. ALSO...FINAL
   VISIBLE SATELLITE PICTURES OF THE DAY INDICATE MORE ISOLATED PATCHES
   OF AGITATED CUMULUS WITHIN THE OPEN WARM/MOIST SECTOR...FROM WHICH
   DEEPER CONVECTION HAS BLOSSOMED INVOF THE CONCHO VALLEY.

   RECYCLED LOW-LEVEL MOISTURE REMAINS IN PLACE E OF THE DRYLINE AND
   S/SE OF THE EFFECTIVE BOUNDARY...WITH 00Z RAOBS INDICATING
   LOWEST-100-MB MEAN MIXING RATIOS AROUND 10-12 G/KG. MID-LEVEL LAPSE
   RATES WILL BE SUFFICIENT TO MAINTAIN MUCAPE AROUND 500-1500 J/KG
   INTO THE OVERNIGHT HOURS. THE DRT 00Z RAOB IS SAMPLING THE
   BEST-DEFINED EML ACROSS THE AREA...SUPPORTING THE STRONGEST BUOYANCY
   TOWARD THE RIO GRANDE RIVER. AFOREMENTIONED CONVECTION EVOLVING FROM
   MULTIPLE FOCI WILL SPREAD EWD ACROSS THE FOREGOING AIR MASS THROUGH
   THE LATE EVENING/EARLY OVERNIGHT HOURS. THIS ACTIVITY WILL
   PRINCIPALLY BE SUSTAINED BY SUFFICIENTLY MOIST/UNSTABLE INFLOW
   IMPINGING UPON LOCALLY UPSCALE-GROWING COLD POOLS AMID 30-45 KT OF
   EFFECTIVE BULK SHEAR.

   GIVEN THE AFOREMENTIONED BUOYANCY/SHEAR PARAMETER SPACE...ISOLATED
   SVR HAIL ACCOMPANYING INCIPIENT CONVECTIVE STAGES AND MORE DISCRETE
   CONVECTIVE MODES WILL BE POSSIBLE...AND A FEW SVR WIND GUSTS MAY
   ALSO OCCUR WITH STRENGTHENING COLD POOLS. THIS WILL AFFECT A LARGE
   PART OF CNTRL TX AND VICINITY. HOWEVER...GIVEN A TENDENCY FOR
   NOCTURNAL COOLING TO SUPPORT GAINS IN BOUNDARY-LAYER STATIC
   STABILITY AND MLCINH MAGNITUDE...ALONG WITH AN OVERALL DEARTH OF
   DEEP/LARGE-SCALE ASCENT AND WEAK LOW-LEVEL FLOW SAMPLED BY AREA
   VWPS...THE SVR-TSTM RISK SHOULD REMAIN ISOLATED. CONVECTIVE TRENDS
   WILL CONTINUE TO BE MONITORED. IF A MORE WIDESPREAD SVR RISK WERE TO
   EVOLVE WITH UPSCALE-GROWING CONVECTION...THEN WW-ISSUANCE
   PROBABILITIES COULD INCREASE.

   ..COHEN/EDWARDS.. 04/20/2016


   ATTN...WFO...FWD...OUN...EWX...SJT...LUB...MAF...

   LAT...LON   31160263 32890162 33839919 33929768 33369636 31599677
               30349790 29849972 29680134 29900249 31160263 

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