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Mesoscale Discussion 1153
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MD 1153 graphic

   Mesoscale Discussion 1153
   NWS Storm Prediction Center Norman OK
   0312 PM CDT Mon Jun 26 2017

   Areas affected...Portions of central/eastern WA...OR...and
   western/northern ID

   Concerning...Severe potential...Watch unlikely 

   Valid 262012Z - 262245Z

   Probability of Watch Issuance...5 percent

   SUMMARY...An isolated threat for strong to locally damaging winds
   will develop this afternoon and evening. Some hail may also occur.
   Watch issuance is not expected due to the overall isolated/marginal
   severe risk.

   DISCUSSION...Recent visible satellite and radar imagery have shown
   an increase in convective coverage along the crest of the Cascades
   into eastern OR. This activity is likely occurring in association
   with large-scale lift attendant to a shortwave trough moving over
   the northern CA/southwestern OR Coast as of 20Z. A seasonably moist
   low-level airmass is in place across the northern Great Basin into
   the northern Rockies per 12Z area soundings and 20Z surface
   observations. Plentiful diurnal heating has allowed surface
   temperatures to warm mostly into upper 80s to mid 90s across lower
   terrain along and east of the Cascades, and combined with modestly
   steep mid-level lapse rates, weak instability (MLCAPE) of 250-1000
   J/kg has developed.

   Modestly enhanced mid-level winds of 30-40 kt associated with the
   mid-level shortwave trough are encouraging similar values of
   effective bulk shear, which will likely be sufficient to support at
   least some thunderstorm organization through the evening hours as
   storms spread northeastward into eastern WA and western/northern ID.
   Steep low-level lapse rates will allow convectively enhanced
   downdraft winds to reach the surface, and isolated strong to locally
   damaging winds will likely be the primary severe threat given DCAPE
   in excess of 1000 J/kg across much of this region. Some marginally
   severe hail may also occur with the strongest updraft cores. Even
   with locally scattered convective coverage expected, the overall
   severe threat will likely remain too isolated/marginal given the
   thermodynamic/kinematic environment present, and watch issuance is
   not expected at this time.

   ..Gleason/Guyer.. 06/26/2017

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

   ATTN...WFO...PIH...MSO...BOI...OTX...PDT...MFR...PQR...

   LAT...LON   44511456 42821493 42521509 42281575 42131657 42091837
               42461881 42851946 43032027 42732116 42052257 42412302
               43082270 44312151 46302147 46742078 47672021 47741733
               47161594 44511456 

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Page last modified: June 26, 2017
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