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Mesoscale Discussion 1365
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   Mesoscale Discussion 1365
   NWS Storm Prediction Center Norman OK
   0318 PM CDT Thu Jul 20 2017

   Areas affected...Portions of Wyoming...far southern
   Montana...extreme southeast Idaho

   Concerning...Severe potential...Watch unlikely 

   Valid 202018Z - 202245Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Convection spreading across portions of the northern
   Rockies vicinity into the early evening will have the potential to
   produce isolated severe wind and hail. Present indications are that
   Watch issuance is unlikely.

   DISCUSSION...Convection continues to increase in coverage and
   intensity from southeast ID to northwest WY and into adjacent MT,
   peripheral to a mid-level speed maximum crossing the northern
   Rockies. Related enhanced ascent, interacting with the northern
   extent of monsoon-related moisture, is enhancing convective 
   coverage -- aided by diurnally enhanced orographic circulations. The
   presence of 25-40 kt of effective shear associated with the speed
   maximum is already supporting semi-organized convective structures,
   which will continue tracking northeastward and eastward into the
   evening hours. Sufficient mid-level moisture exists for high-based
   convection to produce isolated severe wind gusts amid a
   deep/well-mixed boundary layer -- especially where more-defined,
   small bowing convective segments evolve. Steep mid-level lapse rates
   could support some severe hail risk with more isolated, cellular
   structures. However, the overall limited magnitude of boundary-layer
   moisture and associated marginal buoyancy should limit overall
   severe coverage.

   ..Cohen/Coniglio/Hart.. 07/20/2017

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...BYZ...RIW...PIH...

   LAT...LON   42851148 44571011 45450838 44660727 43430733 42420908
               42281071 42851148 

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Page last modified: July 20, 2017
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