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Mesoscale Discussion 840
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   Mesoscale Discussion 0840
   NWS Storm Prediction Center Norman OK
   0135 PM CDT Thu May 25 2017

   Areas affected...Portions of northeastern CO...western/central
   NE...and northwestern KS

   Concerning...Severe potential...Watch possible 

   Valid 251835Z - 252030Z

   Probability of Watch Issuance...40 percent

   SUMMARY...An isolated large hail and damaging wind threat may
   develop over the next several hours. Watch issuance is possible
   depending on convective trends.

   DISCUSSION...18Z surface analysis depicts a cold front arcing from a
   low over north-central SD across parts of central/western NE and
   into northeastern CO. A small cluster of thunderstorms ongoing as of
   1830Z across northeastern CO is probably associated with a minor
   shortwave trough embedded within larger upper troughing extending
   from Saskatchewan into the northern Plains/Rockies and Great Basin.
   Additional thunderstorms will likely form over the next several
   hours across parts of northern/central CO as broad large-scale
   ascent attendant to the upper trough overspreads this region. The
   boundary layer downstream of ongoing convection across the central
   High Plains is becoming well-mixed this afternoon with plentiful
   diurnal heating occurring. Although low-level moisture remains
   somewhat modest with surface dewpoints generally in the mid 40s to
   lower 50s, steep mid-level lapse rates and cool mid-level
   temperatures are contributing to MLCAPE up to 1000 J/kg per latest
   RAP Mesoanalysis. Additional heating may encourage instability to
   increase up to 1500 J/kg along and south of the front by peak
   heating this afternoon.

   Strengthening mid-level west-southwesterly winds associated with the
   mid/upper-level trough will support effective bulk shear values of
   35-45 kt across this region through this evening, which should be
   sufficient for supercell structures. Recent short-term
   convection-allowing model guidance remains unclear regarding the
   coverage and intensity of thunderstorms this afternoon. But, the
   overall parameter space will be favorable for organized updrafts
   with an isolated large hail and damaging wind risk, with at least
   some chance at upscale growth into one or more line segments
   potentially focused along/near the front. If radar/satellite trends
   indicate an increase in convective strength/coverage this afternoon,
   then watch issuance may be needed.

   ..Gleason/Kerr.. 05/25/2017

   ...Please see for graphic product...


   LAT...LON   40300402 41270380 41920309 42200199 41700023 41209944
               40629883 39989891 39259906 38829926 38519996 38510209
               39020337 39600414 40300402 

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