Mesoscale Discussion 0914
   NWS Storm Prediction Center Norman OK
   0220 PM CDT Sun Jun 14 2020

   Areas affected...Portions of western/central ND and
   northwestern/north-central SD

   Concerning...Severe potential...Severe Thunderstorm Watch likely 

   Valid 141920Z - 142115Z

   Probability of Watch Issuance...80 percent

   SUMMARY...The threat for large hail and severe wind gusts should
   increase this afternoon as storms develop. Watch issuance is likely
   in the next couple of hours.

   DISCUSSION...19Z surface analysis shows a 1000 mb low over far
   southeastern MT near the ND/SD border, with a front extending
   northward from this low across far eastern MT. Morning clouds and
   precipitation associated with a lead shortwave trough have delayed
   surface heating a bit, but clearing skies and low-level airmass
   recovery are occurring across northwestern SD and southwestern ND in
   the wake of this activity. Large-scale ascent attendant to another
   small-scale perturbation embedded within broad south-southwesterly
   mid-level flow is supporting agitated cumulus across the Black Hills
   vicinity of western SD and far northeastern WY. As this ascent
   begins to overspread the destabilizing airmass across western ND/SD,
   convection should increase in both coverage and intensity this
   afternoon.

   Current expectations are that surface temperatures in the mid to
   upper 80s across the warm sector will generally be needed to
   overcome a low-level inversion and support surface-based convection,
   which appears increasingly likely by 20-21Z (3-4 PM CDT). Steep
   mid-level lapse rates of 7.5-8.5 C/km which overlie a modestly moist
   low-level airmass to the east of the cold front will support peak
   afternoon MLCAPE of 1500-2500 J/kg. Modest low-level
   veering/strengthening of the wind field quickly transitions to
   mainly speed shear at mid/upper levels, which is supporting 40-50 kt
   of effective bulk shear. This deep-layer shear with a large
   meridional component should prove more than sufficient for
   supercells with at least an isolated large hail threat initially,
   mainly across western ND and northwestern SD. A tornado cannot be
   ruled out early in the convective life cycle while storms remain
   semi-discrete, although the low-level flow is not forecast to be
   overly strong.

   As the front develops slowly eastward this afternoon and evening,
   some upscale growth and clustering of storms may occur into central
   ND and north-central SD as they move east-northeastward. Isolated
   severe and potentially damaging winds appear possible if this
   scenario occurs. Observational trends will be closely monitored for
   signs of robust convective initiation, with Severe Thunderstorm
   Watch issuance likely in the next couple of hours.

   ..Gleason/Guyer.. 06/14/2020

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

   ATTN...WFO...ABR...BIS...UNR...

   LAT...LON   45280367 46100392 47520399 49010398 49020044 47789985
               45939983 45050078 44770267 45280367