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Mesoscale Discussion 1327
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MD 1327 graphic

   Mesoscale Discussion 1327
   NWS Storm Prediction Center Norman OK
   0730 PM CDT Sun Jul 16 2017

   Areas affected...Portions eastern MT and western ND

   Concerning...Severe potential...Watch unlikely 

   Valid 170030Z - 170230Z

   Probability of Watch Issuance...20 percent

   SUMMARY...An isolated threat for strong to locally damaging winds
   may persist this evening with thunderstorms moving across eastern MT
   into western ND. The overall severe threat will likely remain too
   isolated/marginal to warrant watch issuance.

   DISCUSSION...A broken line of convection that formed across the
   higher terrain of southern MT is located over eastern MT as of
   0025Z. A weak surface low is present over eastern MT as well, and a
   trough extends southward from the low across the northern High
   Plains. A very well-mixed boundary layer exists across eastern MT
   into western ND, as evidenced by large temperature-dewpoint spreads
   in surface observations and per inverted-v 00Z observed sounding
   from GGW. Convective downdraft processes may be enhanced by this
   well-mixed boundary layer, with some strong to locally damaging
   winds possible through this evening. West-southwesterly mid-level
   flow does weaken slightly with southward extent across the northern
   High Plains, as the primary upper trough remains over AB/SK. But,
   sufficiently veering/strengthening winds present on VWPs from KGGW,
   KMBX, and KBIS may allow for some updraft organization, with
   effective bulk shear values generally ranging from 30-40 kt.

   Other isolated convection has recently developed across parts of
   western ND along a low-level instability gradient, and this activity
   may also pose an isolated threat for large hail/damaging winds over
   the next several hours. Later this evening a strengthening southerly
   low-level jet across the Dakotas may encourage more scattered to
   numerous thunderstorms to develop, but increasing convective
   inhibition with the loss of daytime heating suggests the overall
   severe threat should slowly diminish, and watch issuance appears
   unlikely at this time.

   ..Gleason/Edwards.. 07/17/2017

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

   ATTN...WFO...BIS...BYZ...GGW...

   LAT...LON   45150668 46040659 47020664 48160733 49020601 49080392
               49070141 48100092 47350127 45910412 45110617 45150668 

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Page last modified: July 17, 2017
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