The first round of severe weather that prompted a severe thunderstorm watch across western South Dakota and parts of southeastern Montana began to weaken Sunday evening, but meteorologists cautioned that a new corridor of strong to severe storms could redevelop Monday.
Sunday evening: storms tapering, but hail and extreme gusts possible
National Weather Service and local forecasters said storm coverage was limited Sunday as an atmospheric cap suppressed widespread development, but the environment still supported the potential for intense, isolated storms. The primary hazard reported for the watch area was large hail, while isolated wind gusts of 60, 70 or even 80 miles per hour could occur with stronger updrafts that do manage to break through the cap.
Officials said most convection was expected to diminish between 6 and 8 p.m. local time, though a few pockets of stronger storms would remain possible into the evening, particularly across the northwestern portions of South Dakota.
Monday: renewed risk as conditions reset
Forecasters expect the atmosphere to recover overnight, allowing for a fresh round of storms to form by midday Monday. Showers and thunderstorms were forecast to develop around noon and advance toward Rapid City, with storm chances rising between about 11 a.m. and 1 p.m. across the hills and then moving into the Rapid City area.
Similar hazards to Sunday are expected on Monday: large hail and strong straight-line winds will be the principal threats, with the potential for an isolated storm to become particularly severe. Temperatures in the region were forecast to climb near 90 degrees Fahrenheit Monday afternoon, providing additional instability for storm development.
- Main threats: large hail and damaging wind gusts.
- Timing: storms expected around midday Monday, with peak chances late morning into afternoon.
- Areas of concern: western South Dakota, including Rapid City and surrounding hill country, and portions of southeastern Montana.
Outlook beyond Monday
After Monday’s heightened risk, conditions are forecast to settle by midweek. Models and forecasters indicated a boundary shifting southward that will help cool and dry the region, with Tuesday and Wednesday expected to be significantly calmer. Temperatures should drop into the lower 80s in the hills and mid-80s elsewhere, with only isolated shower chances south of Interstate 90.
| Day | Primary threats | Timing |
|---|---|---|
| Sunday evening | Large hail; isolated 60–80 mph wind gusts | Most storms fading 6–8 p.m.; isolated cells possible later |
| Monday | Large hail; damaging winds; isolated severe storm | Development around noon; increased risk 11 a.m.–1 p.m. |
| Tuesday–Wednesday | Calmer, isolated showers possible | Mostly dry |
Event planners and residents were advised to monitor local forecasts and watches. Rapid City-area organizers were told that evening activities at the Central States Fair were not expected to be significantly affected Monday evening, though isolated showers could linger southeast of the city in a localized, moderate-risk corridor.
When storms are in the vicinity, people should be prepared to take shelter quickly if warnings are issued and avoid exposed outdoor locations during strong thunderstorms. With hail and very strong wind gusts possible, unsecured outdoor equipment and vehicles may be at risk of damage.
Forecasters said there is reasonable confidence that the severe threat will be focused Monday into the Rapid City area and nearby hill country, but noted that severe weather remains inherently localized and that even capped environments can produce an isolated, intense storm.
