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Mesoscale Discussion 477
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   Mesoscale Discussion 0477
   NWS Storm Prediction Center Norman OK
   1141 AM CDT Tue Apr 30 2019

   Areas affected...Oklahoma...Far North Texas...Far Northwest
   Arkansas...Far Southeast Kansas...Far Southwest Missouri

   Concerning...Severe potential...Tornado Watch likely 

   Valid 301641Z - 301845Z

   Probability of Watch Issuance...80 percent

   SUMMARY...The severe threat is likely to increase across the region
   over the next few hours. A tornado threat, along with wind damage
   and large hail will be possible as cells intensify. A tornado watch
   will likely be needed relatively soon.

   DISCUSSION...The latest surface analysis shows a stationary front
   from north-central Oklahoma extending southwestward into northwest
   Texas. Along and south of the boundary, surface dewpoints are in the
   upper 60s and lower 70s F, which is contributing to a moderately
   unstable airmass. The RAP is estimating MLCAPE values across the
   warm sector in the 2000 to 3000 J/kg range. Along the instability
   gradient, a small cluster of strong to severe thunderstorms is
   developing in north-central to northeastern Oklahoma. This activity
   is expected to continue to move northeastward across northeast
   Oklahoma. The Tulsa WSR-88D VWP shows 0-6 km shear of 35 kt with 0-3
   km storm relative helicity near 270 m2/s2. This shear environment
   will support supercell development associated with a tornado threat.
   The tornado threat will be greatest with cells that track
   northeastward along the front. Large hail and wind damage will also
   be possible with this activity.

   Further to the south across southern Oklahoma, convection is
   beginning to initiate in the vicinity of Ardmore. Some uncertainty
   exists concerning how fast this activity will ramp up this
   afternoon. For this reason, a tornado watch will likely be needed
   over the next hour. The current thinking is that cells will
   gradually increase in coverage and intensity with a severe threat
   developing by 18Z in south-central and east-central Oklahoma. The
   deep-layer shear environment will favor supercell development. In
   addition, RAP forecast soundings gradually increase low-level shear
   this afternoon across east-central Oklahoma, which will become more
   favorable for tornadoes. Large hail and wind damage will also be
   possible with supercells that develop.

   ..Broyles/Hart.. 04/30/2019

   ...Please see for graphic product...


   LAT...LON   34069641 33739740 33829807 34229869 35299872 35849811
               36799653 36959616 37139511 36889458 36049445 35489455
               34749535 34069641 

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