503 FXUS63 KUNR 051116 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 516 AM MDT Thu Jun 5 2025 .KEY MESSAGES... - Two shortwaves will bring shra/TS through Friday - Warmer and drier weather this weekend into early next week - Active southwest flow may develop for the middle of next week && .DISCUSSION...(Today Through Wednesday) Issued at 153 AM MDT Thu Jun 5 2025 07z surface analysis had trough from UT into northeastern WY, which was a reflection of shortwave across western WY into UT per water vapour loop. Regional radar loop shows cluster of shra/TS over WY heading into the CWA. Main forecast concern revolves around disposition of mean upper trough from central Canada to the southwest CONUS. Today/tonight, shortwave moves east/northeast across the CWA with modest QG forcing, but well-defined 800-700mb theta-e advection/frontogenetic forcing focused on the southern half of the area. MUCAPE <250J/kg, which will be insufficient to fuel nice 0-6km bulk shear in place, so TS should behave. Expect cluster of shra/TS to traverse the area today, tapering off this evening. Further north where solar insolation may break out, another day of popcorn convection will occur. LREF/HREF QPF amounts at least 0.50" (50-80% chance) over southern half of CWA. Much lower further north. QPF/PoPs painted to match. Temperatures will be near guidance, but confidence lowest where clouds/precipitation persists most of the day. Friday, the second shortwave swings through the northern Rockies into the central Plains. Best forcing/0-6km bulk shear misses the area to the southwest. 250-500J/kg mean SBCAPE will be released across the southwest half of the CWA, particularly near the Black Hills where terrain convergence will assist. Temperatures will be near guidance. Saturday/Sunday, upper ridge over the Rockies will kick upper trough away with drier northwest flow aloft developing. Several waves will move through with the best chance of weak convection Saturday as a cool front crosses the CWA. Breezy/windy spots behind the front given isallobaric forcing/lower tropospheric forecast soundings. Temperatures will be noticeably warmer Saturday and slightly cooler Sunday. Upper ridge influence will hold firm into Wednesday with temperatures 5-10F above normal. There are signs southwest flow will develop for the second half of next week portending increasingly active weather if moisture return is sufficient. && .AVIATION...(For the 12Z TAFS Through 12Z Friday Morning) Issued At 514 AM MDT Thu Jun 5 2025 A cluster of showers/isolated thunderstorms will affect northeastern WY through southern SD through this afternoon. Areas MVFR/local IFR conditions are expected. Northwestern SD will see scattered showers/isolated thunderstorms with local MVFR conditions today. Tonight, precipitation will taper off from west to east with MVFR/local IFR conditions slowly shifts eastward, but persisting over south-central SD through the period. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION/KEY MESSAGES...Helgeson AVIATION...Helgeson