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Mesoscale Discussion 361
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   MESOSCALE DISCUSSION 0361
   NWS STORM PREDICTION CENTER NORMAN OK
   1148 AM CDT MON APR 11 2016

   AREAS AFFECTED...PORTIONS OF NERN TX...SRN/ERN AR...NRN LA...WRN MS

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 111648Z - 111915Z

   PROBABILITY OF WATCH ISSUANCE...60 PERCENT

   SUMMARY...THE AREA IS BEING MONITORED FOR AN INCREASE IN THE
   SVR-TSTM POTENTIAL...INCLUDING THE RISK FOR SVR HAIL/WIND AND
   POSSIBLY SOME TORNADO RISK. THE ISSUANCE OF A WW WILL BE POSSIBLE
   DURING THE NEXT COUPLE OF HOURS.

   DISCUSSION...A CLUSTER OF CONVECTION THAT DEVELOPED DURING THE
   OVERNIGHT HOURS ACROSS THE LOW ROLLING PLAINS OF NW TX HAS SPREAD
   ENEWD TO CNTRL/SWRN AR LATE THIS MORNING...WITH ADDITIONAL
   CONVECTION TRAILING SWWD TO THE ARKLATEX REGION. ALL OF THIS
   ACTIVITY LIES WITHIN A ZONE OF ASCENT IN THE EXIT REGION OF A
   MID/HIGH-LEVEL SPEED MAX CROSSING THE AREA. LOW-LEVEL ISENTROPIC
   ASCENT IS ALSO ENCOURAGING THE DEVELOPMENT OF ADDITIONAL 
   CONVECTION -- PROBABLY ELEVATED -- E OF THE AFOREMENTIONED
   ESTABLISHED CONVECTIVE CLUSTERS EWD TO THE ARKLAMISS REGION.

   WIDESPREAD MULTI-LAYERED CLOUD DECKS ARE PRESENTLY INHIBITING
   DIURNAL DIABATIC SFC-LAYER HEATING IN THE PRE-CONVECTIVE AIR BENEATH
   A WARM LAYER AROUND 730 MB BASED ON THE 12Z SHV RAOB. HOWEVER...WITH
   SFC DEWPOINTS HOLDING IN THE MIDDLE 60S...CONTINUED TRANSPORT OF
   HIGHER THETA-E AIR FROM THE S...AND AT LEAST SOME POCKETS OF LIMITED
   INSOLATION...THERE WILL BE A GRADUAL TENDENCY FOR CONVECTION TO
   INTENSIFY/BECOME SFC-BASED WHILE SPREADING EWD. STEEP MID-LEVEL
   LAPSE RATES -- ON THE ORDER OF AROUND 7-8 C/KM IN THE H7-H5 LAYER --
   WILL SUPPORT VIGOROUS UPDRAFTS AS MLCAPE INCREASES TO 1000-2000 J/KG
   MLCAPE.

   THE SHV VWP IS SAMPLING AROUND 45 KT OF DEEP SHEAR...SUGGESTING THAT
   ORGANIZED CONVECTIVE ELEMENTS WITH SVR WIND/HAIL WILL BECOME LIKELY
   BY MID-AFTERNOON. AMPLE LOW-LEVEL DIRECTIONAL SHEAR YIELDING AROUND
   300 M2/S2 OF 0-1-KM SRH MAY SUPPORT SOME TORNADO RISK WITH ANY
   SUSTAINED SUPERCELL STRUCTURES...AND LINE-EMBEDDED MESOVORTICES.
   HOWEVER...THE TORNADO POTENTIAL WILL BE DEPENDENT ON CONVECTIVE
   MODE...AND THERE MAY BE A TENDENCY FOR MIXED MODES/LINEAR STRUCTURES
   TO BECOME MORE COMMON LIMITING THE TORNADO RISK TO SOME EXTENT.

   PRESENT INDICATIONS ARE THAT WW-ISSUANCE PROBABILITIES WILL INCREASE
   THROUGH THE AFTERNOON HOURS. HOWEVER...GIVEN THE ANTECEDENT LIMITED
   LOW-LEVEL LAPSE RATES RELATED TO WIDESPREAD CLOUD COVERAGE...THERE
   IS UNCERTAINTY REGARDING THE TIMING OF MORE SUBSTANTIAL INCREASE IN
   SVR RISK. THERE IS SOME POSSIBILITY THAT THIS MAY OCCUR IN THE NEXT
   COUPLE OF HOURS...BUT BY MID-AFTERNOON THE POTENTIAL WILL BE
   GREATER.

   ..COHEN/GOSS.. 04/11/2016


   ATTN...WFO...MEG...JAN...LZK...SHV...

   LAT...LON   33479442 34369255 34639130 34359051 33059016 32129094
               32109254 32299400 32839471 33479442 

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Page last modified: April 11, 2016
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