textproduct: Sioux Falls

KEY MESSAGES

- Some patchy valley fog is possible early Thursday morning. Be prepared for changing visibility on your morning commute.

- Temperature will continue to trend near to above normal into the weekend with highs mainly in the 80s to low 90s.

- Besides some smaller periodic rain chances (20% or less), mostly dry conditions are expected through Sunday.

DISCUSSION

Issued at 137 PM CDT Wed Aug 5 2026

Today will be mostly sunny and quiet under high pressure with light winds and highs in the upper 70s to low 80s. Northwest flow aloft will bring smoke into the region from wildfires out west. The smoke is expected to remain mostly aloft and currently throughout our CWA the air quality is good. For more on air quality and to get an air quality forecast for your location please see AirNow.gov

Patchy valley fog is possible early Thursday morning as winds become light to calm. Fog is most likely east of I-29 over northwest Iowa. Any fog that forms should burn off by mid- morning. As the high pressure moves off to the east this afternoon and evening winds will become southerly. At the same time from the west an upper shortwave will approach the region, strengthening the LLJ. Overnight winds will begin to increase from the west to the east. During the day Thursday good mixing up through the 850 mb level will bring down stronger gusts of 20 to 30 mph for much of the region. Portions of northwest Iowa will remain lighter at 15 to 20 mph gusts. Conditions are expected to be dry and warmer thanks to modest WAA. Highs will range from the low to upper 80s with warmest conditions over central South Dakota.

Thursday night another subtle upper wave will pivot over the region bringing chances for showers and thunderstorms. There are a few trends we will need to monitor over the next 24 to 36 hours. A narrow band of modest moisture return looks to set up over central South Dakota, but areas to the east look to remain fairly dry. Moderate surface based instability of around 1000 J/kg of CAPE will build through Thursday afternoon over central South Dakota. However, as you move east there is an increasingly strong cap in place. Instability above the cap is lacking, so elevated convection would struggle to initiate. So while an isolated strong to severe storm is possible over central South Dakota, confidence in any strong storms making it farther east than US Highway 281 is low. If storms should form it would between roughly 6 pm and midnight.

Friday sees the return of higher dew points in the upper 60s to low 70s. With highs in the 70s to 80s it will be a bit of a muggy day. A series of subtle waves will keep low PoPs in the forecast for much of the day. A more defined wave pivots through Friday evening into Saturday morning bringing chances for more organized convection, mainly east of I-29. Periodic storm chances continue through the rest of the weekend and into the beginning of next week. However, confidence in timing, coverage, and severity of storms is low as this is the point where mid-range guidance begins to diverge.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1233 PM CDT Wed Aug 5 2026

VFR conditions are expected to prevail for this period. Few to scattered clouds in conjunction with wildfire smoke aloft will partially obscure the sky. Winds for the most part during the day today will be southerly and light to light and variable. This evening and through the overnight stronger winds will spread east. By sunrise wide spread gusts of 15-20 kts are expected. Through the day Thursday winds continue to increase with widespread gusts between 20-27 kts. Areas of northwest Iowa will see lower gusts generally 20 kts or less.

FSD WATCHES/WARNINGS/ADVISORIES

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