textproduct: Sioux Falls

KEY MESSAGES

- Hot conditions are expected Friday 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.

- Smoke from upstream wildfires could affect the area Friday and this weekend. 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.

UPDATE

Issued at 848 PM CDT Thu Jul 16 2026

Very few changes to the forecast this period. Winds will be light and variable tonight with warm lows in the upper 60s to low 70s. Patchy areas of fog are possible Friday morning, most likely along water ways and low laying areas. Friday morning winds become southwesterly but remain light at around 10 mph or less. This will usher in drier air that will reduce dew points for areas west of the James River into the low 60s. East of there mid 60s to low 70s are expected for dew points. The lower dew points will result in lower relative humidity values for most of the region. Deep mixing will boost afternoon highs temperatures into the 90s and low 100s, warmest west of Highway 81. Despite slightly lower dew points Heat Index values are still expected to climb into the mid to upper 90s, with localized areas of 100+ west of Highway 81. Since values above 100 F will be localized and limited to a couple hours in the afternoon, have decided to forego a heat headline at this time. Still, conditions will be very hot and dangerous for those working outside without proper hydration and breaks out of the heat. Please continue to check on your friends and neighbors.

Friday morning a weak cold front will be draped from far northeast Minnesota through South Dakota and into Wyoming. This front will gradually begin to push into our CWA around mid-day. As the front continues to progress southeast a modest 800-700 mb layer of moisture will be pushed down into the region from the north. Soundings indicate this layer developing modest instability Friday afternoon. With the weak forcing from the front a few isolated mid- level showers and possibly thunderstorms may develop. Severe weather is not anticipated, and rainfall totals will be minimal at a few hundredths. Showers are most likely to form north of I-90 into southwestern Minnesota in the late afternoon and evening.

One final note: smoke from Canadian wildfires will continue to impact the Midwest over the next several days. While the worst of the smoke will remain over the Great Lakes area, eastern South Dakota and southern Minnesota could begin to see effects from smoke Friday, and especially this weekend. Areas at elevation along the Buffalo Ridge Sunday are most likely to see the worst impacts. Skies could begin to take on a milky look, air quality is likely to decrease somewhat, and you may even be able to smell the smoke. Sensitive populations may need to take precautions such as remaining in doors or wearing a mask.

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 /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 620 PM CDT Thu Jul 16 2026

VFR conditions are expected to prevail through the period. Skies will be mostly clear. Southerly winds will become light and variable overnight. By mid-day Friday a cold front will be draped roughly from northeast to southwest South Dakota. Behind the front winds become northerly and lightly breezy.

FSD WATCHES/WARNINGS/ADVISORIES

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