Mesoscale Discussion 1477
   NWS Storm Prediction Center Norman OK
   0417 PM CDT Thu Aug 13 2020

   Areas affected...northwest MN...far eastern ND

   Concerning...Severe potential...Watch possible 

   Valid 132117Z - 132245Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Convective initiation appears imminent between Grand Forks
   and Fargo as of 415pm CDT.  Isolated to scattered thunderstorms are
   forecast to develop as the cap weakens further.

   DISCUSSION...Visible satellite imagery shows the initial signs of
   glaciation with storms near the Red River (415pm CDT).  A mid-level
   accas plume has overspread northwest MN into southeast ND on the
   southern fringe of large-scale ascent associated with a mid-level
   shortwave trough over Manitoba.

   Surface analysis places a warm frontal zone from northeast ND
   east-southeastward into northern MN near Duluth.  Temperatures south
   of the boundary are in the 80s with lower 70s dewpoints and
   temperatures have remained generally in the mid-upper 70s over far
   northern MN where a stratus deck has impeded stronger surface
   heating.  Objective analysis/RAP forecast soundings show a very to
   extremely unstable airmass located over southeast ND into adjacent
   parts of MN with MLCAPE 4000-4500 J/kg.  The limiting factors for
   severe are the weak large-scale forcing for ascent and modest
   effective shear (ranging from 20 to 30 kt).  The strongest
   deep-layer shear is relatively confined near and north of the warm
   front where storm organization potential will be enhanced due to the
   stronger shear.  Storms may eventually be capable of transient
   rotation primarily near the warm front where flow is locally backed
   with southeast surface winds.  The stronger storms that can become
   established may be capable of a large hail/severe gust threat. 
   Although tornado potential will likely be muted by modest deep-layer
   shear, appreciable curvature to the hodograph near the warm front
   may yield a localized tornado risk for 1-2 hours before storm cold
   pools negatively interfere with one another.

   ..Smith/Guyer.. 08/13/2020

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

   ATTN...WFO...FGF...

   LAT...LON   47509724 48779617 49499484 48329442 46249570 46039672
               46319725 47509724