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Mesoscale Discussion 1781
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   Mesoscale Discussion 1781
   NWS Storm Prediction Center Norman OK
   0534 PM CST Mon Dec 04 2017

   Areas affected...Portions of eastern OK and western/central AR

   Concerning...Severe Thunderstorm Watch 519...

   Valid 042334Z - 050100Z

   The severe weather threat for Severe Thunderstorm Watch 519

   SUMMARY...An isolated threat for mainly strong to damaging winds
   should continue across WW 519 for the next several hours. Downstream
   watch issuance into more of western/central AR will probably not be

   DISCUSSION...Mosaic radar imagery from 2330Z depicts a broken line
   of thunderstorms extending along and just ahead of a surface cold
   front across eastern OK into far northwestern AR. Several other
   thunderstorms have recently developed across southwestern AR within
   the open warm sector. A few cells within the broken line have
   exhibited supercell characteristics over the past several hours,
   with sporadic large hail and strong/damaging winds being reported.
   The airmass immediately downstream of this ongoing convection should
   remain favorable for maintenance of severe thunderstorms in the
   short term, as MLCAPE around 500 J/kg and effective bulk shear
   values of 40-50 kt are present across western AR. A tornado cannot
   be completely ruled out given veering low-level winds supporting
   effective SRH around 275-325 m2/s2. However, the primary severe
   threat will likely transition to strong/damaging winds as the
   surface cold front overtakes ongoing convection, with these
   thunderstorms quickly growing upscale into a southeastward-moving
   squall line.

   While some severe threat may exist to the east of WW 519, cooler
   surface temperatures and less low-level moisture is present with
   eastward extent across central AR. Resultant instability likewise
   wanes into central AR. Coupled with the loss of diurnal heating
   which should further reduce already weak instability, the small
   spatial severe threat to the east of WW 519 may become too marginal
   over the next several hours to justify a new WW in central AR.

   ..Gleason.. 12/04/2017

   ...Please see for graphic product...


   LAT...LON   34869577 35509514 36459470 36459248 35419248 33959344
               33619418 34029517 33979592 34489610 34869577 

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