Mesoscale Discussion 1753
   NWS Storm Prediction Center Norman OK
   0536 PM CDT Fri Oct 23 2020

   Areas affected...Western MT...ID Panhandle...Far eastern WA

   Concerning...Heavy snow 

   Valid 232236Z - 240230Z

   SUMMARY...Low elevation heavy snow with rates of 1 to 2 inches/hour
   will continue to spread east-southeast from eastern WA/Spokane area
   and the ID Panhandle across a swath of western MT this evening,
   before diminishing from west to east.

   DISCUSSION...Heavy snow has been ongoing the past few hours across
   low elevations of eastern WA and the ID Panhandle along the I-90
   corridor, including the greater Spokane area. Intense 850-650 mb
   warm advection downstream of a shortwave trough ejecting southeast
   from southern British Columbia is yielding strong ascent below the
   dendritic growth zone that is located between 650-500 mb. This
   corridor of strong forcing for ascent will shift east-southeast this
   evening across a swath of western MT. The eastern edge of the heavy
   snow has reached the Missoula Valley and should reach the Helena
   area in the next couple hours. Peak snowfall rates are expected this
   evening, before diminishing from west to east tonight as supported
   by 15Z SREF/12Z HREF guidance.

   ..Grams.. 10/23/2020

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

   ATTN...WFO...TFX...MSO...OTX...

   LAT...LON   46651736 46831766 47581781 48071755 48281702 48341610
               48071496 47761344 47071171 46471141 46081146 45961281
               46041439 46091576 46391649 46651736