textproduct: Sioux Falls

KEY MESSAGES

- Warm and humid conditions continue this weekend. Afternoon heat indices will approach 100F along portions of the Missouri River Valley today and Sunday as temperatures climb into the 90s.

- Isolated strong to severe storms are possible between 9pm and 3am this evening and night along and west of the James River. Large hail up to 1 inch in diameter and damaging winds to 60 mph are the main hazards.

- Low chances (<= 25%) for rain will persist through the weekend and Monday. Chances for rain increase up to a 50-80% chance for Tuesday. Severe storms could accompany this chance for rain, so continue to monitor the latest forecast.

- Above normal temperatures and additional chances (20-40%) for rain persist for the rest of next week.

DISCUSSION

Issued at 229 PM CDT Sat Aug 29 2026

Clearing skies and warm temperatures have returned to the area this afternoon. Temperatures will warm a little bit more to the 80s to low 90s with heat indices up to the upper 80s and 90s. A few locations along the Missouri River Valley are expected to see heat indices touch 100F this afternoon before temperatures cool as the sun begins to set. A few light showers/sprinkles persist across parts of southwest Minnesota but will push east of the area over the next hour or two. Attention then turns to the evening timeframe where additional chances for rain look to return to the area. Showers and some storms look to develop across western Nebraska and southwest South Dakota. These showers will push eastwards into an increasingly stable airmass sitting over the forecast area. At the same time, vertical shear values will be weakening as well. Still, can't rule out the potential for an isolated strong storm or two between 9pm to 3am. Should a strong storm or two develop, it could produce large hail up to the size of a quarter (1 inch) and damaging winds to 60 mph IF the storm can tap into the boundary layer. The most likely location to see these potentially stronger storms is along and west of the James River. Elevated showers look to persist through the rest of the night.

Sunday will be a similar day with high temperatures once again expected to warm to the upper 80s and 90s. This will again push heat indices to the 90s with a few locations along the Missouri River again seeing heat indices touch 100F during the afternoon timeframe. A stronger shortwave trough will be passing mainly through Montana throughout the day. This wave however will take on a negative tilt and push into northeastern Montana and northwestern North Dakota. Severe storms are possible in this area but is much more questionable for our area. Especially as the cold front tied to this wave pushes into the forecast area due to limited moisture/instability and capping just ahead of the front. Thus, have left PoPs dry for Sunday evening and night.

The cold front will push through the area Sunday night through Monday morning. With the front just south of the area, Monday looks to be a continuation of warm and dry conditions with highs warming to the 80s to up to about 90F. Chances for rain look to return to the forecast on Tuesday as a weak shortwave trough pushes into the Northern Plains. The mass response from this wave will return the previously mentioned boundary northwards as a warm front. The ensembles generally show a 50-80% chance for rainfall totals to exceed a tenth of an inch. This will likely be contingent on where the front sets up and if the cap can be broken or not. As of now, latest machine learning (ML) guidance shows a 5-10% chance for strong to severe storms on Tuesday. Tough to say if trends will hold over the next few days so will keep an eye on Tuesday going forward.

Chances (20-40%) for rain persist for the rest of the week along with a continuation of above average. Highs look to remain in the mid to upper 80s Wednesday through Saturday. ML guidance shows low chances (<= 5%) for strong to severe storms. Thus, could see a continuation for strong to severe storms for the rest of the week but confidence in specific details remains low.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1240 PM CDT Sat Aug 29 2026

A few light showers/sprinkles begin the TAF period early this afternoon north of I-90. Should see any chance for these light showers/sprinkles wane over the next few hours. Clearing skies are expected for the rest of the afternoon hours. Another round of showers and isolated storms is possible this evening and into the overnight hours. The showers and isolated storms will move in from the west near to after 02z this evening. As such, have included a PROB30 group in KHONs TAF. There remains uncertainty how far east the showers can last, so have left out of all other TAFs at this time. Dry conditions are expected for the morning hours tomorrow. Winds will be backing through the rest of today for most locations before turning out of the southwest to end the period.

FSD WATCHES/WARNINGS/ADVISORIES

SD...None. MN...None. IA...None. NE...None.