647 FXUS63 KUNR 221706 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 1106 AM MDT Sun Jun 22 2025 .KEY MESSAGES... - Slight risk (2 out of 5) of severe thunderstorms later this afternoon/evening, especially over southern SD - Unsettled next week with seasonal temperatures with a slight risk (2 out of 5) of severe thunderstorms Tuesday && .UPDATE... Issued at 1008 AM MDT Sun Jun 22 2025 Low clouds are sticking around longer than originally anticipated, and so temperatures are cooler. Lowered highs today across parts of the western SD plains, including southwestern SD, where some CAMs show storms strengthening. Therefore, confidence is low on severe weather developing there this evening. && .DISCUSSION...(Today Through Saturday) Issued at 149 AM MDT Sun Jun 22 2025 07z surface analysis had cool front from central MN to KICR to northeastern CO with a low pressure over northeastern CO. Water vapour loop had upper ridge over the eastern CONUS and trough over the northwest CONUS. CWA had southwest flow aloft with next wave of interest over eastern ID/UT. Ahead of these features early this morning, 50kt low-level jet igniting TSRA (2-3KJ/kg MUCAPE, weak effective shear) over south-central SD with regional radars showing additional convection developing in/near MT/WY/ND borders per 700mb theta-e advection (1KJ/kg MUCAPE, 35-45kt effective bulk shear). Expect best convection to be northeast/north of CWA overnight, but can`t rule out a stronger storm mainly over northwestern SD. Effect of ID/UT wave the main short term forecast concern. Today/tonight, ID/UT wave lifts northeast with modest QG- forcing. Northeast CO low will move along cool front into eastern SD pushing cool front south of CWA tonight. Persistent theta-e advection ahead of it will promote isolated/scattered shra/TS in the north this morning and then over the western SD plains later this afternoon/evening. Buoyancy will average <1KJ/kg in post frontal environment with rapidly increasing values ahead of the cool front. 0-6km bulk shear best post-frontal. CAMs show active storms over southwestern SD (Black Hills downstream convergence per northerly winds helping convective initiation) later this afternoon, moving east into south-central SD this evening. Strongest convection should be associated with front east of CWA. Thus, marginal risk (1 out of 5) of severe thunderstorms reasonable over the CWA. High temperatures this afternoon will be tricky with post-frontal low clouds squashing potential temperatures in the northwest, so didn`t stray far from guidance. Next week, upper trough moves east of the area with west/southwest flow aloft and several perturbations zipping through the flow. Return flow Tuesday will promote increasing buoyancy and sufficient shear for the possibility of severe thunderstorms per SPC Day 3 slight risk. After that, harder to pinpoint focused areas of precipitation and/or active thunderstorms, but it`s June so wouldn`t be surprised to see spritzes of strong/severe TSRA with last nights CSU MLP portraying that scenario. && .AVIATION...(For the 18Z TAFS Through 18Z Monday) Issued At 1103 AM MDT Sun Jun 22 2025 MVFR ceilings will lift northeast this afternoon leaving mainly VFR conditions behind. Isolated to scattered showers and thunderstorms will become more numerous this afternoon and early evening with local IFR conditions, particularly across southern SD. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ UPDATE...Pojorlie DISCUSSION/KEY MESSAGES...Helgeson AVIATION...Smith