ZCZC SPCSWOMCD ALL ACUS11 KWNS 111904 SPC MCD 111904 SDZ000-NDZ000-MTZ000-WYZ000-112100- Mesoscale Discussion 1498 NWS Storm Prediction Center Norman OK 0204 PM CDT Tue Jul 11 2023 Areas affected...Parts of eastern MT...southwestern ND...northeastern WY...and western SD Concerning...Severe potential...Severe Thunderstorm Watch likely Valid 111904Z - 112100Z Probability of Watch Issuance...80 percent SUMMARY...Storms capable of producing very large hail and severe winds should spread eastward across the area this afternoon and evening. A severe thunderstorm watch will likely be issued in the next hour or two. DISCUSSION...Latest visible satellite imagery shows gradually deepening boundary-layer cumulus and isolated convective development across parts of central into eastern MT this afternoon. Continued diurnal heating/destabilization of a moist air mass (lower 60s dewpoints) and DCVA preceding a shortwave trough over northwestern MT should allow for additional thunderstorm development during the next couple hours. 40-50 kt of midlevel westerly flow (per regional VWP data) atop low-level southeasterlies will yield a long/straight hodograph (45-55-kt effective shear) supportive of discrete /semi-discrete splitting supercells. Very large hail up to 2.5 inches in diameter and locally severe winds will be possible with these storms. With time, cell mergers and localized upscale growth into several organized clusters will be possible, with a continued risk of large hail and increasing damaging-wind threat. A severe thunderstorm watch will likely be issued during the next hour or two for parts of the area. ..Weinman/Mosier.. 07/11/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BIS...UNR...CYS...BYZ...GGW...RIW... LAT...LON 44900659 45720724 46760745 47650750 48250740 48480716 48540677 48500623 48120520 47710431 47120352 46560292 46040248 45290195 44780169 44430156 44150148 43580150 43290177 43090219 43050302 43120344 43300390 43520438 43720478 43990531 44480609 44900659 NNNN