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Mesoscale Discussion 890
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   Mesoscale Discussion 0890
   NWS Storm Prediction Center Norman OK
   1147 PM CDT Sat May 27 2017

   Areas affected...Southern/eastern OK...North TX...Western AR

   Concerning...Tornado Watch 279...

   Valid 280447Z - 280545Z

   The severe weather threat for Tornado Watch 279 continues.

   SUMMARY...The severe threat will likely continue beyond the 05Z
   issuance time of WW 279. A new watch and/or local watch extensions
   across portions of southern/eastern OK and western AR will be
   necessary, with watch issuance into north TX possible within the
   hour or two.

   DISCUSSION...An intense cluster of thunderstorms is ongoing across
   southern OK at 0430Z. This activity is being focused along an
   outflow-enhanced cold front that extends into western portions of
   north TX, and some backbuilding has recently been noted into
   portions of Clay and Wichita Counties in TX. Strong to extreme
   buoyancy continues to feed into this cluster, with effective shear
   more than sufficient to maintain embedded supercell structures with
   a threat of large hail and damaging wind. The increasingly linear
   mode is not particularly favorable for tornadoes, but with strong
   instability and increasing low-level shear into the overnight hours,
   some threat for a tornado or two with embedded circulations will

   With an increasing low-level jet (approaching 50 kts according to
   KFWD VWP) and approaching vort max from the west, the thunderstorm
   cluster is likely to maintain its intensity well past the 05Z
   expiration time of WW 279, with some additional backbuilding
   possible into western north TX, and slow southward propagation into
   north-central TX overnight. The severe threat will also continue
   across eastern OK into northwest AR with ongoing intense storms.
   With these factors in mind, a new watch and/or local watch extension
   will likely be needed across portions of southern/eastern OK and
   western AR shortly, with new watch issuance into north TX possible
   in the next 1-2 hours.

   ..Dean/Guyer.. 05/28/2017

   ...Please see for graphic product...


   LAT...LON   33979875 34339803 35639567 36349475 36289383 35449393
               34409467 33549572 33539679 33579774 33579832 33639864

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