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Mesoscale Discussion 1110
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   Mesoscale Discussion 1110
   NWS Storm Prediction Center Norman OK
   0335 PM CDT Wed Jun 21 2017

   Areas affected...Portions of eastern ND...northeastern SD...and
   western/central MN

   Concerning...Severe potential...Watch possible 

   Valid 212035Z - 212300Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Isolated large hail and damaging winds may occur with
   thunderstorms expected to develop later this afternoon/early
   evening. Watch issuance is possible.

   DISCUSSION...20Z surface observations indicate a weak cold
   front/wind shift extending from southern Manitoba into eastern ND,
   and continuing southwestward across SD. A warm front is located
   north/south along the ND/MN border, continuing into southwestern MN
   and IA. As an upper low pivots eastward across
   Saskatchewan/Manitoba, increasing (50-70+ kt) mid-level westerly
   flow is beginning to overspread the Dakotas and western MN.
   Large-scale ascent attendant to this mid-level jet will likely
   foster convective initiation along the cold front in eastern ND and
   perhaps northeastern SD over the next several hours. This activity
   would then develop eastward into western/central MN through the
   evening.

   As of 2030Z, the low-level airmass has destabilized in a narrow
   corridor between the cold/warm fronts. There is some potential for
   the warm front to shift eastward into more of western/central MN
   over the next several hours as southerly low-level flow strengthens
   across this region in the wake of morning convection. Low-level
   moisture characterized by surface dewpoints in the upper 50s to mid
   60s across the warm sector remains somewhat of a limiting factor, as
   MLCAPE should generally increase to no more than 1000-1500 J/kg
   immediately ahead of the cold front.

   However, strong 40-55+ kt of effective bulk shear will likely
   support supercells with initial development, and both large hail and
   damaging winds may occur. Some potential for upscale growth into one
   or more bowing line segments may take place with the front acting as
   a linear forcing mechanism. A tornado or two may also occur with any
   discrete convection crossing the warm front where low-level flow may
   be locally backed to southeasterly. Radar and observational trends
   will be monitored through the remainder of the afternoon/early
   evening for possible watch issuance.

   ..Gleason/Weiss.. 06/21/2017

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

   ATTN...WFO...DLH...MPX...FGF...ABR...BIS...

   LAT...LON   45559954 46709860 47799801 49059782 49079614 49049528
               49469529 49439472 48919462 48799356 47149387 45069596
               44959846 45559954 

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Page last modified: June 21, 2017
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