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Mesoscale Discussion 1015
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   Mesoscale Discussion 1015
   NWS Storm Prediction Center Norman OK
   0346 PM CDT Tue Jun 13 2017

   Areas affected...ofk

   Concerning...Severe potential...Watch likely 

   Valid 132046Z - 132315Z

   Probability of Watch Issuance...80 percent

   SUMMARY...A severe threat is expected to develop late this afternoon
   from southern Nebraska northeastward into far southeastern South
   Dakota and northwest Iowa. An isolated tornado threat along with a
   potential for large hail and wind damage will be possible as cells
   initiate and increase in coverage over the next couple of hours.
   Weather watch issuance will likely be needed.

   DISCUSSION...The latest surface analysis shows a 999 mb low over
   central Nebraska with a moist airmass in place to the east of the
   low. Surface dewpoints are in the mid 60s to lower 70s F across
   southern and eastern Nebraska into western Iowa. This is
   contributing to a corridor of strong instability with MLCAPE values
   estimated by the RAP to be in the 2000 to 4000 J/kg range across the
   MCD area. In addition, a belt of strong low-level flow is analyzed
   by the RAP across eastern Nebraska extending north-northeastward
   into far southeastern North Dakota and northwestern Iowa. As this
   feature strengthens over the next few hours, new surface-based cells
   are forecast to initiate from near Norfolk south-southwestward to
   near Grand Island. Forecast soundings across this area late this
   afternoon show moderate deep-layer shear with some directional shear
   in the low-levels. This is creating 0-6 km shear in the 30 to 40 kt
   range according to the RAP which will support supercell development.
   The shear along with strong instability and steep low to mid-level
   lapse will be favorable for large hail and wind damage with
   supercells and short line segments. Hail greater than 2 inches in
   diameter along with a tornado threat may accompany the more dominant

   ..Broyles/Hart.. 06/13/2017

   ...Please see for graphic product...


   LAT...LON   43829647 43649729 42329826 40829922 40199892 40259729
               42399557 43199540 43829647 

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