030 FXUS63 KUNR 290452 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 1052 PM MDT Sun Jun 28 2026 .KEY MESSAGES... - Severe thunderstorms with large hail and damaging winds expected overnight across western SD, mostly east of the Black Hills. - Strong winds expected Monday, with elevated to near-critical fire weather conditions. - Cooler Monday, but gradual warmup through the week. && .UPDATE... Issued at 1052 PM MDT Sun Jun 28 2026 A Severe Thunderstorm Watch is now in effect for portions of our south-central South Dakota plains overnight. Very strong deep- layer shear in excess of 65kts will favor supercells, and while a shallow stable layer may be present at the surface suggesting storms may be elevated, very thick mid-level CAPE profiles in forecast soundings with over 3,000 J/kg MUCAPE possible will support a very large hail threat. Convection may also be enhanced by gravity waves increasing a damaging wind threat with time, with some HRRR and RRFS guidance hinting at gusts over 80 MPH in far eastern portions of our CWA. A non-zero tornado risk exists as well with notable SRH, but the elevated nature of the storms may keep this risk low. Will also be watching for swaths of very heavy rain with storm training, with localized flash flooding not impossible...especially if storms train over areas that saw significant rainfall last night in our southern/eastern counties. Largely went with NBM and WPC guidance in the forecast, but adjusted PoPs and QPF to better match current radar trends and the new 00z HREF suite including CAMs. Breezy conditions remain expected Monday, and no changes were made to the ongoing WIND ADVISORY. These winds, along with minimum afternoon RH values of 12-18 percent, may support near-critical fire weather conditions especially from the Weston County area into the far southwestern South Dakota plains. Some areas have seen recent rainfall but may still carry critical fuels...confidence remains just low enough that we will continue to monitor these conditions and not issue a Red Flag Warning with this update. && .DISCUSSION...(This Evening Through Sunday) Issued at 1208 PM MDT Sun Jun 28 2026 Current Water Vapor and upper air models show the upper low currently over north central MT, with southwest flow over the forecast area. 17Z Surface analysis shows a boundary running from northwestern SD down into southeastern WY. Winds are currently light out of the south to southwest. Radar has some light returns in northwestern SD moving northeast into ND. Main concern in the near-term will be potential for severe thunderstorms tonight into Monday morning. Mostly dry conditions are expected this afternoon, but southeasterly LLJ ramps up this evening into the overnight hours, bringing moisture into the region. Surface low is expected to develop over northeastern CO and move northeastward into the area by tonight. As low enters the region and LLJ increases, strong to severe storms are expected to develop. While we could see some showers/storms develop in the early evening, HREF and HRRR show the stronger storms starting up between 03-06Z. CAMS currently show strong to severe storms developing in southwestern SD and the Black hills in this timeframe, then moving northeast. Thermal profiles will support elevated storms with hail being the main threat from these, however strong to severe wind gusts cannot be ruled out. Monday will be dry but windy, as strong mixing will support wind gusts 45 to 55 mph. A Wind Advisory has been issued for much of western SD, including the foothills late morning into the early evening. Another shortwave is progged to move through the central/northern plains late Tuesday into Wednesday, supporting the potential for some showers/storms. Southwest flow continues though the week, with weak disturbances prompting near daily chances for at least isolated precipitation the latter half of the week. Upper high in southeastern CONUS also builds over the week, supporting a gradual warmup. Temperatures climbing into the 90s will be possible Thursday through Saturday. && .AVIATION...(For the 00Z TAFS Through 00Z Monday Evening) Issued At 545 PM MDT Sun Jun 28 2026 VFR conditions generally remain expected this evening, overnight, and Monday across most of the region, but breezy diurnal SW winds this evening will relax and give way to the potential for isolated to scattered thunderstorms overnight, some of which may be severe. High-res guidance supports initial development between 02-04z/8-10pm over the southern Black Hills or southwest South Dakota, with storms tracking northeast from there through the early morning hours Monday (likely clearing KRAP by 10z/4am). Any storm could bring brief IFR conditions, wind gusts over 40kts, and hail. Light showers will be possible outside of this main corridor of storms with some CAMs wetter than others even back west into KGCC, but confidence remains low enough to only continue a PROB30 group for -TSRA at KRAP with no other predominant precip in the forecast at the TAF terminals for now. Some lower VFR to MVFR clouds are also possible Monday morning for a few hours in south- central South Dakota. Skies trend clearer over the course of the day Monday regionwide with breezy conditions developing after 14z/8am in northeast Wyoming and after 17z/11am in western South Dakota with gusts as high as 30-35kts. Confidence in VFR conditions is high. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...Wind Advisory from 10 AM to 8 PM MDT Monday for SDZ012-013- 025>027-030-031-041-042-072>076. WY...None. && $$ UPDATE...KSmith DISCUSSION...Dye AVIATION...KSmith