ZCZC SPCSWOMCD ALL ACUS11 KWNS 090037 SPC MCD 090037 SDZ000-NEZ000-MTZ000-WYZ000-090200- Mesoscale Discussion 0891 NWS Storm Prediction Center Norman OK 0737 PM CDT Tue Jun 08 2021 Areas affected...Eastern Wyoming western South Dakota and the western Nebraska Panhandle. Concerning...Severe potential...Watch possible Valid 090037Z - 090200Z Probability of Watch Issuance...40 percent SUMMARY...New storm development across eastern Wyoming may pose a risk for severe winds later this evening across South Dakota and western Nebraska. Considerable uncertainty on storm severity remains given southward surging outflow and the high-based nature of storms. A weather watch may be needed. DISCUSSION...Evening water vapor imagery showed a compact shortwave trough ejecting across the central Rockies and far western High Plains. Ascent and stronger flow aloft from this trough has begun to overspread the western edges of the warm and unstable airmass across eastern Wyoming. Recent RADAR and satellite trends have shown an increase in convective coverage/strength in the last 30 min. Plentiful buoyancy (2000-3000 J/kg of MLCAPE) from SPC mesoanalysis will support robust updrafts as high-based storms across eastern Wyoming continue to develop eastward into deeper moisture this evening. Given the deep and well-mixed PBL, damaging wind gusts appear to be the primary threat. Large hail, while initially limited, may become a greater threat later this evening as storms encounter greater buoyancy farther east. However, weak vertical shear( 20-30 kts) and a tendency to grow upscale may limit the potential for larger hail. To the north and east, a cluster of storms ongoing across southwestern North Dakota may also interfere with developing convection in the next couple of hours. Southwestward surging outflow will tend to undercut storms as they move eastward casting doubt on how widespread of a severe threat may develop. Regardless, with large buoyancy and the potential for strong downdrafts, some severe risk will likely develop this evening. A watch may be needed should intensification trends continue. ..Lyons/Thompson.. 06/09/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...UNR...CYS...BYZ... LAT...LON 41990471 42190525 43260516 44370528 45440411 45570305 45390245 45090173 43820177 43170286 42740330 42400386 41990471 NNNN