textproduct: Sioux Falls

KEY MESSAGES

- Hot conditions will continue this afternoon and again Sunday where heat indices could climb to around 100, especially west of Highway 81. 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.

- Wildfire smoke will return over the weekend. While lower surface concentrations are expected, any sensitive groups should begin to monitor their local air quality.

- 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.

UPDATE

Issued at 356 AM CDT Fri Jul 17 2026

Taking a look across the area this morning, mostly clear and quiet conditions persist. Similar the last few days, a few patchy spots of areas of valley fog have developed this morning mainly due to lighter winds and linger low level moisture. While this fog won't likely hang around long, there could be some temporary visibility reductions through mid-morning so make sure to drive with care. Otherwise, the focus continues to be on the heat today. Similar to the past few days, highs will likely peak in the low to upper 90s with the warmest conditions slightly offset from the highest dew points. However, with a southwesterly wind in place and weak warm air advection aloft (WAA); we could get just enough of a push to break into low 100 degree heat index values across parts of the area this afternoon. With this in mind, went ahead and issued an area- wide heat advisory from 1 pm to 9 pm so make sure to stay hydrated! Lastly, a cold front will progress through the area this afternoon and evening. While this could potentially lead to few spotty showers mainly along the Highway-14 corridor, not expecting any stronger activity at this time.

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 /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 630 AM CDT Fri Jul 17 2026

Mostly VFR conditions will persist this TAF period. Taking a look at satellite imagery, patchy valley fog continues across the area promoting shallow MVFR to LIFR vsby at times. Should see the fog gradually erode by mid-morning. Otherwise, VFR cigs and vsby will return with light southwesterly winds ahead of an approaching cold front. While some spotty showers will be possible, none of our TAF sites will be affected besides a few wind shifts. Lastly, southeasterly winds will become more northeasterly with the frontal passage.

FSD WATCHES/WARNINGS/ADVISORIES

SD...Heat Advisory from 1 PM this afternoon to 9 PM CDT this evening for SDZ038>040-050-052>071. MN...Heat Advisory from 1 PM this afternoon to 9 PM CDT this evening for MNZ071-072-080-081-089-090-097-098. IA...Heat Advisory from 1 PM this afternoon to 9 PM CDT this evening for IAZ001>003-012>014-020>022-031-032. NE...Heat Advisory from 1 PM this afternoon to 9 PM CDT this evening for NEZ013-014.