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Area Forecast Discussion
Issued by NWS Rapid City, SD
Issued by NWS Rapid City, SD
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998 FXUS63 KUNR 180448 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 1048 PM MDT Wed Jul 17 2024 .KEY MESSAGES... - Near average temperatures with a daily chance of thunderstorms through the weekend. Isolated severe storms possible. - Trending warmer and drier for the first half of next week. && .DISCUSSION...(This Evening Through Wednesday) Issued at 140 PM MDT Wed Jul 17 2024 Current analysis shows northwesterly flow aloft, resulting from an upper ridge building to the west of the forecast area and a trough sweeping across the Great Lakes Region. At the surface, high pressure over the ern Dakotas/wrn MN is producing light northeasterly surface winds over the forecast area. Dewpoints in western SD are in the mid-50s to around 60F and in the 40s over northeastern Wyoming. MLCAPE has risen to around 500J/kg over much of the area, with a max of >1500J/kg over southwestern SD and near the eastern slopes of the Black Hills. Due to the instability, scattered thunderstorms have already initiated along the convergence zone over the central and southern Black Hills, with large hail reported earlier this afternoon near Hot Springs. Damaging wind gusts will also be possible today. Storm motion for the stronger storms coming off the hills has been nearly straight south, with the weaker storms moving a bit more to the southeast. Storms have also developed over the higher terrain to the west and southwest of the forecast area. Storms developing in the vicinity of the Bighorns may track into Campbell county Wyoming and then eastward into Weston county as the afternoon progresses, and then possibly continuing eastward into southwestern SD this evening. The setup looks to be much the same for Thursday, with the best chances for strong to severe storms again over and near the Black Hills, extending southward into southwestern SD. A stronger shortwave will round the upper ridge Thursday night, dropping across the western Dakotas on Friday. This will bring scattered thunderstorms to much of the area Friday afternoon/evening with again a wind/hail threat. The ridge will becomes a bit more amplified over the weekend with northerly flow aloft over the Plains. Embedded impulses will keep chances for thunderstorms in forecast each day. Early next week, eastern the Pacific trough will nudge the ridge to the east, resulting in warmer/drier conditions across the forecast area. && .AVIATION...(For the 06Z TAFS Through 06Z Thursday Night) Issued At 1048 PM MDT Wed Jul 17 2024 Isolated storms will affect portions of the area Thursday through Thursday night, resulting in local MVFR conditions and gusty, erratic winds. Otherwise VFR conditions are expected through the forecast period. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION/KEY MESSAGES...10 AVIATION...13