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Mesoscale Discussion 908
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   Mesoscale Discussion 0908
   NWS Storm Prediction Center Norman OK
   0256 PM CDT Thu Jun 10 2021

   Areas affected...far northeast MT...western ND

   Concerning...Severe potential...Tornado Watch likely 

   Valid 101956Z - 102130Z

   Probability of Watch Issuance...95 percent

   SUMMARY...Convective initiation is expected between 20-21 UTC along
   the dryline over eastern MN near the ND border.  Explosive growth
   into significant-severe producing supercells is forecast late this
   afternoon into the early evening.

   DISCUSSION...Visible-satellite imagery shows a swelling band of
   agitated cumulus along the dryline over far eastern MT near Sydney. 
   Temperatures immediately east of the dryline have warmed into the
   lower 80s with a deepening boundary layer featuring low to mid 60s
   deg F dewpoints.  The 18 UTC Glasgow, MT raob showed a very steep
   700-500 mb lapse rate (8.6 deg C/km).  Modifying the raob for 19 UTC
   surface conditions east of the dryline near the ND/MT border (i.e.,
   Sydney, MT) yielded 3300 J/kg MLCAPE with very little convective
   inhibition remaining.  As the cap erodes, expecting explosive
   updraft growth quickly evolving into a few discrete supercells. 
   Giant hail (3+ inches in diameter) is possible with the stronger
   storms as the organize and move northeast into a less deeply mixed
   and more moisture rich environment near the warm front.  Supercell
   tornadoes will be possible in vicinity of the warm front, in
   addition to the hail/severe gust hazard.  Other isolated storms are
   forecast to eventually develop southward along the dryline into
   parts of southwest ND and northwest SD.  Large to giant hail will be
   the primary hazard with these storms before additional thunderstorm
   development into a severe squall line evolves later this evening.

   ..Smith/Guyer.. 06/10/2021

   ...Please see for graphic product...


   LAT...LON   48980713 48560749 48100717 48090558 47640477 45790370
               45970205 48380212 48970265 48980713 

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