Mesoscale Discussion 1384
   NWS Storm Prediction Center Norman OK
   0614 PM CDT Fri Jun 20 2025

   Areas affected...portions of southeastern Montana...southwestern
   North Dakota...far northwest South Dakota

   Concerning...Severe Thunderstorm Watch 447...

   Valid 202314Z - 210045Z

   The severe weather threat for Severe Thunderstorm Watch 447
   continues.

   SUMMARY...Severe wind and hail will accompany ongoing supercells and
   multicells over the next few hours. Upscale growth into an MCS may
   eventually occur. Should this occur, conditions are favorable for
   bow-echo development with a high-end severe wind threat.

   DISCUSSION...A band of multicells and supercells continues to track
   eastward across far southeastern Montana, atop an unstable boundary
   layer and strong vertical wind shear. 22Z mesoanalysis and a special
   2055Z ICECHIP sounding depict well over 1000 J/kg MLCAPE, with
   large, curved, and elongated hodographs supporting around or over 50
   kts of effective bulk shear with 250+ effective SRH. Ahead of these
   storms, low-level moisture increases substantially, especially
   around central ND, where mesoanalysis depicts well over 2000 J/kg
   MLCAPE. As such, the ongoing storms should continue eastward with a
   threat for severe wind and hail in the short-term. A tornado is also
   possible with any discrete supercells given strong low-level shear,
   especially after 01Z, when the storms are poised to move into better
   low-level moisture.

   It is unclear if and/or when these storms merge cold pools and grow
   upscale into a singular MCS. Surface observations and mesoanalysis
   depict multiple surface and/or low-level boundaries in place that
   may aid in upscale growth. However, a plethora of earlier and recent
   CAM guidance diverges in their solutions regarding later evolution
   of ongoing storms. Some members show storms remaining as supercells,
   with others depicting the development of an MCS. Should the later
   scenario occur, the very steep mid-level lapse rates and
   aforementioned vertical shear profile would highly support bow echo
   development with efficient severe wind production, including the
   possibility of multiple 75+ mph wind gusts.

   ..Squitieri.. 06/20/2025

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

   ATTN...WFO...ABR...BIS...UNR...BYZ...GGW...

   LAT...LON   45740496 46500520 46920516 47380457 47500387 47420204
               46820095 45960068 45540137 45350236 45250333 45170388
               45170431 45740496 

   MOST PROBABLE PEAK TORNADO INTENSITY...85-115 MPH
   MOST PROBABLE PEAK WIND GUST...75-90 MPH
   MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN