Mesoscale Discussion 0638
   NWS Storm Prediction Center Norman OK
   0236 PM CDT Tue May 19 2020

   Areas affected...portions of western and central MT and adjacent
   parts of east-central ID

   Concerning...Severe potential...Watch possible 

   Valid 191936Z - 192130Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Thunderstorm activity is expected to increase over
   southwest MT this afternoon and shift north/northeast through this
   evening. Isolated strong gusts and hail will be possible, and a
   watch may be needed in the next couple of hours.

   DISCUSSION...Convection over the higher terrain of southwest MT and
   into neighboring portions of ID has been deepening early this
   afternoon, with a couple of recent lightning flashes noted near
   Lemhi County ID and Beaverhead County MT. To the east, a surface low
   is located across eastern MT. Boundary layer moisture has been
   increasing across the High Plains on southeasterly low level flow,
   and wrapping around the backside of the surface low. This has
   allowed surface dewpoints to reach as high as the low 50s as far
   west as Fergus and Blaine Counties in MT, with mid to upper 40s
   across much of western MT into ID. Steep midlevel lapse rates are in
   place atop this modest boundary layer moisture, aiding in weak
   destabilization across the region (MUCAPE around 500-1500 J/kg).
   With additional heating, more widespread thunderstorm development is
   expected over higher terrain. Low level winds are rather weak, but
   strong mid/upper level southwesterly flow is contributing to 40+ kt
   effective shear. This should allow for some organized storm
   structures as convection moves north/northeast. Long, straight
   hodographs and aforementioned steep midlevel lapse rates indicate
   large hail potential. Furthermore, a deeply mixed boundary layer
   with inverted-v sub-cloud thermodynamic profiles could foster strong
   to locally severe wind gusts.

   ..Leitman/Guyer.. 05/19/2020

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

   ATTN...WFO...BYZ...GGW...TFX...MSO...

   LAT...LON   48750999 48840903 48740860 48000860 47630871 46610911
               46150954 45561042 44981187 44841296 44901411 45471501
               45971514 46601496 47501370 48301150 48541073 48750999