textproduct: Sioux Falls

KEY MESSAGES

- Hottest conditions are most likely Friday and again Sunday where heat indices could climb to around 100, especially west of I-29. Saturday should see a slight break from the heat as winds turn northerly behind a weak front.

- Very patchy morning valley fog is possible daily, but widespread dense fog remains unlikely. Fog could reduce visibility below two miles at times.

- Smoke from upstream wildfires could affect the area Saturday into Sunday but confidence is a bit low on this for now. The better chance will likely be near and east of the Buffalo Ridge Sunday morning.

- Precipitation is very unlikely (less than 10%) through Saturday night. Isolated to scattered shower and storm chances return Sunday evening and night, but confidence is low on details.

DISCUSSION

Issued at 1247 PM CDT Thu Jul 16 2026

Upper level flow goes through a touch of a transition Friday into early next week. The first will be a glancing blow from some stronger northwest flow aloft that drops south through northern MN. This will bring a weak front into the area Friday night into Saturday. Ahead of this front temperatures should warm quite a bit with some enhanced mixing as surface winds turn a bit southwest. This should lead to highs more widespread in the mid and upper 90s. With dew points expected to be in the 60s, heat indices in the afternoon could approach 100 degrees.

By Friday night winds will turn more northerly which will allow for a bit of a break from the heat for many. Highs will likely range from the mid 80s in southwest MN to the mid 90s closer to the Missouri River.

As the next wave approaches the Canadian border Sunday, surface winds will turn southerly and bring hotter temperatures back to the area. The hottest will be west of I-29 while east of I-29 the return flow will be slower to set up. The combination of temperatures and humidity may push heat indices above 100 near and west of highway 81.

Ahead of this wave later Saturday night into Sunday morning some mid level moisture and weak instability may allow for some ACCAS showers/very isolated thunder. Will have to watch trends through the day Sunday as this mid level moisture could linger and bring some enhanced cumulus and spotty showers throughout the day. Very low confidence in this right now however.

As this wave moves through ND into MN Sunday night another front will sag south and may have enough forcing, instability and moisture to allow isolated to scattered showers and storms to develop, mainly north of I-90. Confidence remains a bit low, but an isolated severe storm will be possible.

Monday is a tough call on temperatures and precipitation chances. Model agreement on surface frontal position not real high and this will play a decent role in how hot it gets. Monday could be another day with heat indices above 100, especially south of I-90. Will be a bit of a wait and see, especially considering how temperatures have been coming up short of expectations for several days now.

Tuesday into Thursday should see spotty chances for showers and storms with near to a bit below normal temperatures, generally highs in the 80s and lows in the upper 50s to mid 60s.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1155 AM CDT Thu Jul 16 2026

VFR through the period. Some diurnally driven cumulus about 4-6 kft will dissipate around sunset. Patchy early morning fog in low lying areas remains possible.

FSD WATCHES/WARNINGS/ADVISORIES

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