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Mesoscale Discussion 1045
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   MESOSCALE DISCUSSION 1045
   NWS STORM PREDICTION CENTER NORMAN OK
   0531 AM CDT WED JUN 17 2015

   AREAS AFFECTED...PORTIONS OF ERN TX...ERN OK...WRN AR

   CONCERNING...TORNADO WATCH 306...

   VALID 171031Z - 171200Z

   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 306 CONTINUES.

   SUMMARY...TORNADO WATCH 306 IN TEXAS WILL LIKELY BE ALLOWED TO
   EXPIRE ON SCHEDULE AT 1200Z. PRESENT INDICATIONS ARE THAT
   ADDITIONAL/DOWNSTREAM TORNADO WATCH ISSUANCE WILL BE UNLIKELY IN THE
   SHORT-TERM.

   DISCUSSION...REGIONAL VWPS SUGGEST THAT LOW-LEVEL SHEAR REMAINS
   RELATIVELY STRONG BENEATH 30-35 KT OF FLOW AROUND 1 KM AGL WITHIN
   THE ERN SEMICIRCLE OF T.D. BILL. THIS IS ESPECIALLY THE CASE IN
   PROXIMITY TO AND JUST N OF AN E/W-ELONGATED ZONE OF WEAK
   BAROCLINICITY ARCING FROM E-CNTRL TX INTO SWRN LA...OWING TO THE
   RELATIVELY BACKED/ELY NEAR-SFC WIND COMPONENT THAT IS ALSO ENHANCING
   LOW-LEVEL SRH. FURTHERMORE...RICH MOISTURE CONTINUES TO BE DRAWN NWD
   ACROSS E TX...WITH MIDDLE 70S SFC DEWPOINTS EXTENDING NWD FROM THE
   GULF COAST TOWARD THE BAROCLINIC ZONE -- ENHANCING LOW-LEVEL THETA-E
   AND MARGINAL BUOYANCY.

   A PAIR OF FEEDER BANDS ASSOCIATED WITH OCCASIONAL LIGHTNING HAVE
   EVOLVED INVOF WEAK CONFLUENCE AXES NEAR AND S OF THE BAROCLINIC ZONE
   AMIDST THE STRONG SHEAR. YET...SINGLE-SITE RADAR VELOCITY DATA HAVE
   INDICATED NOTHING MORE THAN WEAK...TRANSIENT CYCLONIC SHEAR
   ZONES...WITH LITTLE IN THE WAY OF SUSTAINED DISCRETE/SEMI-DISCRETE
   CELLS PER BASE REFLECTIVITY DATA. AS SUCH...DESPITE THE VERTICAL
   SHEAR PROFILES RESULTING IN SOME CONDITIONAL RISK FOR ONE OR TWO
   BRIEF TORNADOES -- SPREADING NWD INTO PARTS OF ERN OK AND WRN AR
   WITH TIME TODAY -- CONFIDENCE IN CONTINUATION OF SUCH POTENTIAL
   BEYOND THE 1200Z EXPIRATION TIME OF TORNADO WATCH 306 IS LOW. THE
   LACK OF A SUBSTANTIAL INFLUX OF MID-LEVEL DRY AIR -- PER WATER VAPOR
   LOOPS -- AND RELATED LACKING INCREASE IN POTENTIAL
   INSTABILITY/TORNADO-ENHANCING STORM-SCALE PROCESSES MAY BE
   DETRIMENTAL TOWARD THE SUPPORT OF A GREATER TORNADO RISK. 

   AS SUCH...ADDITIONAL/DOWNSTREAM TORNADO WATCH ISSUANCE IS NOT
   CURRENTLY PLANNED...THOUGH COORDINATION WITH THE AFFECTED WEATHER
   FORECAST OFFICES ADDRESSING THIS ISSUE WILL LIKELY BE INITIATED IN
   THE NEXT COUPLE OF HOURS. LATER TODAY...DIURNAL HEATING OF THE MOIST
   BOUNDARY LAYER BETWEEN RAIN BANDS PERIPHERAL TO T.D. BILL MAY PROVE
   SUFFICIENT FOR SOME UPTICK IN CONVECTIVE INTENSITY AND PERHAPS A
   RISK FOR ONE OR TWO BRIEF TORNADOES ROUGHLY WITHIN THE NERN QUADRANT
   OF T.D. BILL AND VICINITY. SUCH POTENTIAL WILL BE ADDRESSED IN
   SUBSEQUENT MCD ISSUANCE THIS MORNING.

   ..COHEN/GOSS.. 06/17/2015


   ATTN...WFO...LCH...SHV...TSA...HGX...FWD...OUN...EWX...

   LAT...LON   28889582 29169678 30579701 32709682 34239665 34709535
               34069434 30569443 29429475 28889582 

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Page last modified: June 17, 2015
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