Mesoscale Discussion 1435
   NWS Storm Prediction Center Norman OK
   0230 PM CDT Sun Aug 09 2020

   Areas affected...eastern North Dakota and northwest Minnesota

   Concerning...Severe Thunderstorm Watch 423...

   Valid 091930Z - 092100Z

   The severe weather threat for Severe Thunderstorm Watch 423
   continues.

   SUMMARY...Thunderstorms capable of strong thunderstorm winds, large
   hail, and a tornado or two will move east through the afternoon
   across eastern North Dakota. This threat will persist into northwest
   Minnesota before weakening across north-central into northeast
   Minnesota later this afternoon.

   DISCUSSION...Thunderstorms have developed/strengthened across
   northeast North Dakota along an eastward advancing cold front.
   Additional thunderstorms have developed in advance of the cold front
   along horizontal convective rolls and on the north side of a slowly
   southward moving outflow boundary remnant of early day elevated
   convection. These thunderstorms will continue through the afternoon
   as strong-to-extreme instability (2000-4000 J/kg) and effective
   layer shear between 35 and 50 knots remains in place. The kinematic
   environment will remain supportive of embedded transient supercells
   and supercell-like structures before eventually evolving into more
   multi-cell/line-segment structures. However, given the degree of
   instability and a low-level vorticity reservoir along the front, a
   tornado or two will remain possible over the next couple of hours.
   Otherwise, strong winds and large hail will be likely with the
   strongest thunderstorm cores.

   With time the thunderstorms across northern areas of the watch will
   move into an increasingly less thermodynamically-favorable
   environment as most-unstable CAPE decreases to the order of 1000
   J/kg in the wake of early morning convection and widespread remnant
   cloud cover.

   Farther south, thunderstorm coverage and evolution remains somewhat
   uncertain. Ongoing development should continue within the existing
   severe thunderstorm watch, with initial storm motions to the east.
   With time, however, uncertainty related to the
   development/evolution/strength of cold pools yields lower confidence
   with eventual storm motion/evolution. Some model guidance suggests
   stronger thunderstorm cold pool development and an eventual
   southward turn, taking storms into northeast South Dakota. If this
   scenario becomes apparent, an additional severe thunderstorm watch
   may be needed across portions of northeast South Dakota or
   west-central Minnesota.

   ..Marsh.. 08/09/2020

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

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

   LAT...LON   46069918 48619680 48379443 45569599 46069918