SPC AC 160559

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1259 AM CDT Thu Jul 16 2020

   Valid 171200Z - 181200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF SOUTHEAST ND...FAR NORTHEAST SD AND WESTERN/CENTRAL MN...

   ...SUMMARY...
   Severe thunderstorms are expected across portions of the northern
   Plains into the Upper Midwest Friday afternoon into early Saturday
   morning. At this time, damaging wind gusts and hail appear to be the
   primary hazards associated with this activity. A more conditional
   threat for a few tornadoes also will exist.

   ...Northern Plains into the Upper Midwest...

   Forecast guidance has been fairly consistent the past several cycles
   bringing a compact shortwave impulse embedded in a larger-scale
   upper trough across the northern Plains and Upper Midwest Friday
   afternoon into early Saturday. At the surface, low pressure will
   develop eastward across the Canadian prairies and a trailing cold
   front will shift eastward from eastern MT into the Dakotas and MN
   during the forecast period. Ahead of the surface front, strong
   southerly low level flow will transport rich boundary layer moisture
   poleward. Combined with evapotranspirative process, surface
   dewpoints in the mid 60s to low 70s seem reasonable. A plume of
   steep midlevel lapse rates will also overspread the region, and
   aided by strong boundary layer heating, MLCAPE values from 3000-4000
   J/kg appear likely.

   Vertically veering wind profiles will result in 35-45 kt effective
   shear. Vigorous thunderstorm development is expected by mid-to-late
   afternoon across central ND, quickly becoming well-organized and
   severe. Storm mode, at least initially, remains a little uncertain.
   Shear and thermodynamic profiles will support supercells, but how
   long convection remains discrete is in question. Forecast soundings
   indicate large, curved hodographs with effective SRH between 250-300
   m2/s2 and mean mixing ratio values greater than 16 g/kg. Any
   discrete supercells that do develop, and maintain discrete
   characteristics certainly would pose a threat for damaging wind,
   large hail and a few tornadoes.

   Eventually, upward development into a forward-propagating bow is
   expected, given strong frontal forcing and an increasing
   southwesterly low level jet during the evening. This should result
   in a move widespread damaging wind threat as convection tracks
   east/southeast along the instability gradient from the eastern
   Dakotas into MN. Widespread severe gusts are possible given the
   forecast extreme instability, steep low level lapse rates amid PW
   values from 1.5-2.0 inches, and model indications of a
   well-developed cold pool.

   ..Leitman.. 07/16/2020

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