ZCZC SPCSWOMCD ALL ACUS11 KWNS 272328 SPC MCD 272328 MTZ000-WYZ000-280030- Mesoscale Discussion 1279 NWS Storm Prediction Center Norman OK 0628 PM CDT Thu Jun 27 2019 Areas affected...Parts of southeastern Montana and adjacent northeastern Wyoming Concerning...Severe potential...Watch unlikely Valid 272328Z - 280030Z Probability of Watch Issuance...20 percent SUMMARY...Isolated supercell development is possible through the 6-8 PM MDT time frame, accompanied by at least a risk for severe hail and locally strong surface gusts. It is not clear that a severe weather watch will be needed, but trends will continue to be monitored for this possibility. DISCUSSION...Relatively moist, northeasterly upslope flow coupled with insolation appears to have contributed to moderate boundary-layer destabilization across portions of southeastern Montana and adjacent northeastern Wyoming, north/northeast of the Bighorn Mountains. This is occurring in the presence of at least weakly rising mid-level heights, and inhibition associated with very warm elevated mixed-layer air. However, forcing associated with orography and weak low/mid-level warm advection may be supporting attempts at thunderstorm initiation, perhaps most prominently across the southern Rosebud/southwestern Powder River county vicinity. Southwesterly deep-layer ambient mean flow is a somewhat modest 20 kts or so across this region, but pronounced veering of winds with height is contributing to strong deep layer shear supportive of supercells, given sustained storm development. Into the 28/00-02Z frame, this appears at least possible, with storms posing a risk for severe hail and localized strong surface gusts. It remains unclear how long any such activity will persist, once inhibition for boundary layer parcels increases further with the loss of daytime heating. ..Kerr/Guyer.. 06/27/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...UNR...BYZ... LAT...LON 46610826 46340581 45290468 44850642 44980699 45140775 45490840 46610826 NNNN