textproduct: Sioux Falls

KEY MESSAGES

- Areas of patchy fog will continue through mid-morning mainly along our waterways and low lying spots. Be prepared for temporary visibility reductions.

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

- 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.

UPDATE

Issued at 326 AM CDT Sun Aug 30 2026

Taking a look across the area, the forecast remains on track with the strongest activity continuing to progress across northcentral and northeastern SD this morning. While the quieter conditions persist across our area this morning, can't completely rule out the development of some "popcorn" showers and non-severe storms towards daybreak as the LLJ strengthens across the U.S. Highway-20 corridor. With increasing dPVA developing ahead of an approaching shortwave, decided to slightly increase POPs through about mid-morning mainly along the highway-20 before this developing activity pushes eastwards.

Otherwise, another hot and humid day is ahead with highs mainly in the upper 80s to mid 90s. This combined with dew points in the upper 60s to low 70s will likely lead to heat index values in the low to upper 90s for most areas and a few spotty lower 100s around the Missouri River Valley. While some spots could briefly touch heat advisory criteria, decided that things would be just isolated enough to forgo a heat headline at this time. Nonetheless, moderate to major heat risk is expected this afternoon especially across the Missouri River Valley and portions of northwestern IA so make sure to stay hydrated and limit any prolonged outdoor activities!

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 temperatures. 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 /06Z TAFS THROUGH 06Z MONDAY/

Issued at 1250 AM CDT Sun Aug 30 2026

Isolated showers and storms are possible along the Highway 20 corridor early this morning, but confidence is low on this potential so only put in a PROB30 group for -SHRA at KSUX to account for this. Patchy fog has occasionally developed in a few places so far tonight, and this will continue into the daybreak hours. Widespread issues are not expected, but the best chances for fog overnight will generally reside around the Highway 14 corridor, though confidence was not high enough to include any at KHON.

Other than the potential for a few light showers east of I-29 during the daytime hours today, dry conditions are expected through the rest of the period. Winds will be mainly light and variable through the mid morning hours, then become mostly out of the southwest as winds pick up to around 7-10 kts this afternoon. Winds will begin to turn more west-northwest in south-central South Dakota towards the end of the period as frontal boundary moves into the area.

FSD WATCHES/WARNINGS/ADVISORIES

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