ZCZC SPCSWOMCD ALL ACUS11 KWNS 221950 SPC MCD 221950 MTZ000-222215- Mesoscale Discussion 1326 NWS Storm Prediction Center Norman OK 0250 PM CDT Thu Jul 22 2021 Areas affected...Much of central Montana Concerning...Severe potential...Watch possible Valid 221950Z - 222215Z Probability of Watch Issuance...40 percent SUMMARY...Thunderstorms are expected to gradually increase and intensify across southwestern into central Montana through 3-6 PM MDT, accompanied by at least some risk for severe hail and wind. More substantive strengthening and organization, accompanied by increasing potential for strong surface gusts, may not occur until after 6 PM MDT, generally northeast of the Lewistown area. DISCUSSION...Forcing for ascent, associated with a weak perturbation migrating around the periphery of mid-level ridging centered over the Four Corners, appears to be aiding deepening convective development and the initiation of thunderstorms across the mountains of southwestern into central Montana. This is occurring near the southern fringe of stronger flow associated with the westerlies, which includes west-southwesterly winds around 500 mb on the order of 40-50 kt. Lower/mid-tropospheric lapse rates across this region continue to steepen in response to insolation and perhaps weak mid-level cooling, and moisture appears sufficient to support weak to modest CAPE on the order of 500-1000 J/kg. This should be enough to support a gradual further increase in convective coverage and intensity through the next few hours, with at least some potential for stronger storms to pose a risk for hail and locally strong surface gusts. In time, a more substantive risk for organized severe weather may gradually develop, as consolidating convectively driven cold pools contribute to the evolution of an organizing convective system in the presence of the strong deep-layer shear. This seems most probable as activity spreads northeast of the Lewistown area by or shortly after 00Z, with severe weather potential increasingly more rapidly thereafter, as strong northeasterly low-level inflow increasingly emanates from a hotter and more moist environment across northeastern Montana. ..Kerr/Hart.. 07/22/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BYZ...GGW...TFX... LAT...LON 46741198 48450859 48130723 46850687 45461098 46741198 NNNN