ZCZC SPCSWOMCD ALL ACUS11 KWNS 191722 SPC MCD 191722 WYZ000-192115- Mesoscale Discussion 1876 NWS Storm Prediction Center Norman OK 1222 PM CDT Tue Oct 19 2021 Areas affected...portions of eastern/central Wyoming Concerning...Heavy snow Valid 191722Z - 192115Z SUMMARY...Ongoing moderate to heavy precipitation will gradually transition to snow this afternoon across central and eastern WY impacting travel conditions. Snow rates above 1 inch per hour with occasional reductions in visibility due to heavy and blowing snow are possible. DISCUSSION...As of 1700 UTC, WV imagery showed the core of a well-defined upper low was located near the western CO, UT and WY borders. To the north and east of the upper low, large-scale forced ascent was supporting the development of widespread stratiform precipitation across much of western and central Wyoming. Over the last hour, regional radar imagery showed additional banded precipitation developing ahead of the low from the vicinity of KRIW to KLAR. Likely in response to increasing lift near a region of strong 700 mb frontogenesis, as well as orographic ascent, additional precipitation development/intensification within this band appears likely over the next several hours. Surface temperatures across much of Wyoming remain just above freezing suggesting initial precip type will be rain below 7k feet. However, as column saturation takes place, dynamic cooling and increasing low-level cold advection from surface pressure falls ahead of the upper low should result in a transition to snow by early afternoon. As the upper low continues eastward along the CO/WY border, strong height falls (60-90 DM/12 hr) should support moderate to heavy snow within the developing frontogenetic band as it wraps north/northwestward around the low. Hi-res guidance and regional model soundings show support for snow rates near or exceeding 1 inch per hour through the afternoon driven in part by steep mid-level lapse rates near the cold core of the upper low. Additionally, weak convective buoyancy as well as negative EPV (indicative of slant-wise instability) suggest some potential for convective elements/banding favorable for locally higher snow rates through the afternoon. While the transition from rain to snow is likely to be gradual, moderate to heavy snow appears likely across much of central and eastern Wyoming through the afternoon. The potential for heavy snow and gusty north winds may result in occasional blowing snow/low visibility disruptive to travel. Weakening ascent and increasingly dry mid-level air should end the heavy snow threat as the upper low shifts to the northeast this evening. ..Lyons/Bunting.. 10/19/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...UNR...CYS...RIW... LAT...LON 43590504 43330483 42870478 42530471 42240473 41850484 41670516 41580560 41700621 42100671 42460760 42580804 42860833 43260838 43730775 43820720 43810640 43790598 43590504 NNNN