ZCZC SPCSWOMCD ALL ACUS11 KWNS 152020 SPC MCD 152020 NEZ000-SDZ000-MTZ000-WYZ000-152245- Mesoscale Discussion 1480 NWS Storm Prediction Center Norman OK 0320 PM CDT Mon Jul 15 2019 Areas affected...portions of eastern Wyoming...southwest South Dakota...western Nebraska Concerning...Severe potential...Severe Thunderstorm Watch likely Valid 152020Z - 152245Z Probability of Watch Issuance...80 percent SUMMARY...Storm coverage will increase this afternoon/evening across portions of the central/northern High Plains. Severe hail and wind are the main threats, and a severe thunderstorm watch issuance is likely. DISCUSSION...An upper-level disturbance is moving over western South Dakota and northwest Nebraska while another disturbance is moving over western Wyoming. These disturbances are helping to provide forcing for ascent and aiding convective initiation along with insolation, terrain, and surface boundaries. The best buoyancy is located across western Nebraska and south/east of the Black Hills in South Dakota where surface dewpoints are in the 50s to upper 60s F and temperatures in the 80s to low 90s F. Storms will move eastward off the higher terrain in Wyoming and onto the High Plains this afternoon/evening. Additional development is also possible along the cold front in South Dakota and along surface convergence ahead of this (possibly a pre-frontal trough). Supercells are possible, at least initially, given the 40-50 knots of effective bulk shear across the area, but upscale growth and a mixed storm mode are likely this evening with the upper-level forcing. Storms will likely intensify with time as they move into better instability. Large hail and damaging wind gusts are the main threats and a severe thunderstorm watch issuance is likely for a large portion of the MCD. ..Nauslar/Dial.. 07/15/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LBF...UNR...CYS...BYZ...RIW... LAT...LON 41730110 41040225 41040328 41250421 41610519 42300602 42940648 43480655 45050560 45510536 45620464 45430389 44300234 43570164 43320087 42940012 42739983 42549975 42270001 42060043 41730110 NNNN