textproduct: Sioux Falls

KEY MESSAGES

- Increased confidence in severe storm chances this evening and early overnight. Damaging winds to 75 to 85 mph are possible. Hail will be a secondary threat, possibly to the size of quarters.

- Extreme Heat Warning for areas along south of I-90 and along/west of Hwy 75 this afternoon into Sunday evening. Elsewhere a Heat Advisory remains in effect. Heat indices will peak in the upper 90s to around 110F each day, hottest in the warning area. If confidence in higher heat indices Sunday increases, additional upgrades are possible.

- While details are uncertain and confidence remains low, if storms develop Sunday evening into Sunday night, some may be strong to severe with damaging winds, isolated large hail and locally heavy rain possible.

- Still a good chance for highs in the 90s next week in most locations. Additional heat headlines are possible.

DISCUSSION

Issued at 117 PM CDT Sat Jul 25 2026

Heat:

Not much change as dew points in the upper 60s to mid 70s provide the area with an oppressive environment. As temperatures rise into the 90s today and Sunday, heat indices will jump to between 100-110 degrees in most locations. The hottest conditions continue to look to be along the James and Missouri River valleys.

For now Monday through Wednesday should see highs generally in the 90s but with a bit less humidity. This will keep the heat index in the 90s as well. Will have to keep an eye on the dew points trends as a few more degrees of moisture will push heat indices above 100.

A wave moving through on Wednesday will likely bring slightly cooler air into the area so the second half of the week may not be quite as hot.

Thunderstorms:

Overall a capping inversion will be in place for the area through the afternoon, so development is not expected. One exception may be in and around Gregory/Charles Mix counties where model soundings hint at possibly breaking the cap. If this can happen, an isolated storm with the potential for wind gusts around 70 mph are possible. CAPE values only running about 500-1500 J/kg with fairly weak shear, but with a very dry subcloud layer. Otherwise, development should take place west of the area and move in after about 6-8 pm. This cluster of storms will likely be a bit pulsy, but with better instability and still a fairly significant sub cloud dry layer wind gusts to 75 mph will be likely with the potential for a cold pool to develop. Hail to the size of quarters will also be possible, but wind will be the main threat. Many of the latest 12z models are jumping on this wind threat and the HRRR has been very consistent bringing this wind threat right down I-90 this evening.

Some lingering showers are possible from midnight into early Sunday morning, but are not expected to be severe and may even have trouble reaching the ground with a significant dry layer below. Still a lot of question marks regarding the severe threat tomorrow afternoon and tomorrow night. For now a significant amount of dry air in the low to mid levels should provide enough capping to avoid afternoon thunderstorm development. If a storm could develop, 2000 J/kg CAPE, 30-40 knots of deep layer shear and a significant dry layer in the lower levels would support wind gusts to 75 mph and hail to the size of half dollars. Otherwise during the later evening and overnight hours the models are really backing off on any potential for the area and keeping the isolated to scattered activity to the northeast.

A wave will move through the area Wednesday into Thursday morning and be the next chance for showers and thunderstorms. This will be the next threat for possible severe storms. The main threat for showers and thunderstorms should come on Thursday.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1216 PM CDT Sat Jul 25 2026

Fog and stratus have just about cleared from northwest IA. Otherwise the next concern will be a cluster of thunderstorms that will move through the area tonight. The better chances will be between 6 pm and midnight. The main hazard from these storms will be potential wind gusts of 75+ mph. Better chances near and west of the James River before 9 pm, and east of the James River from 9 pm to midnight. Outside of any thunderstorms, VFR conditions are expected.

FSD WATCHES/WARNINGS/ADVISORIES

SD...Heat Advisory until 8 PM CDT Sunday for SDZ038>040-052>056-061- 062. Extreme Heat Warning until 8 PM CDT Sunday for SDZ050-063>065- 068>071. Extreme Heat Warning until 8 PM CDT Sunday for SDZ057>060-066- 067. MN...Heat Advisory until 8 PM CDT Sunday for MNZ071-072-080-081-089- 090-097-098. IA...Heat Advisory until 8 PM CDT Sunday for IAZ001>003-013-014-021- 022-032. Extreme Heat Warning until 8 PM CDT Sunday for IAZ012-020-031. NE...Extreme Heat Warning until 8 PM CDT Sunday for NEZ013-014.