Area Forecast Discussion
Issued by NWS Rapid City, SD
Issued by NWS Rapid City, SD
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920 FXUS63 KUNR 200814 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 214 AM MDT Mon May 20 2024 .KEY MESSAGES... - Widespread showers/isolated thunderstorms today/tonight. - Potential for light snow accumulations for higher elevations of the Black Hills tonight. - Active pattern continues through Memorial Day holiday weekend. && .DISCUSSION...(Today Through Sunday) Issued at 212 AM MDT Mon May 20 2024 Current surface map places low across northeastern South Dakota with cold front into the southern Nebraska Panhandle. Water vapor shows upper trough over the Rockies/Great Basin with southwest flow over the forecast area. Showers expected to increase across the area later this morning into early afternoon with robust 850-600mb frontogenesis associated with a period of enhanced upper divergence. Highest rainfall amounts set up from central Wyoming into the Black Hills area. HREF precipitation is showing 80-100% probability of >0.25" around the Black Hills and a 30-50% probability of 0.50". Frontogenesis wanes this evening as shortwave moves through the central Rockies. The shortwave tracks through Nebraska Tuesday, with surface low deepening over Minnesota. Northern portion of deformation zone will bring widespread showers/thunderstorms over south central South Dakota tonight through Tuesday morning with rainfall amounts of 0.50"-1.00". Showers continue over the rest of the area as secondary impulse rotates through eastern Wyoming/western South Dakota. Thermal profiles show lowering of web bulb temperatures tonight, with transition to snow for the higher elevations of the Black Hills. Some snow accumulation is possible, mainly above 5000 ft msl. HREF probability of accumulated snowfall (assuming 10:1 SLR) shows 80-100% probability of >1" and 40-60% of >3" for areas above 6000ft msl. Active pattern continues through the weekend with a daily chance of showers/thunderstorms. A weak impulse crosses the area Wednesday with a few showers. There is a better chance of showers/thunderstorms on late Thursday into Friday and again lateinto Friday followed by another late Saturday into Sunday.Saturday into Sunday as stronger shortwaves swing through the area. && .AVIATION...(For the 06Z TAFS Through 06Z Monday Night) Issued At 1013 PM MDT Sun May 19 2024 Breezy northwesterly winds will continue behind cold front overnight, gusting to over 35 kts on portions of the SD plains. Winds will gradually decrease Mon morning. VFR conditions can be expected overnight into Monday. Chances for showers will increase from west to east across northeast WY and southwest SD during the late morning and afternoon on Monday, with local MVFR conditions expected in the afternoon. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION/KEY MESSAGES...7 AVIATION...JC