textproduct: Sioux Falls

KEY MESSAGES

- After a brief reprieve today, hotter conditions resume on Sunday and likely Monday where heat indices could climb into the low 100s.

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

- Wildfire smoke returns today. Temporary reductions in visibility will be possible through Sunday especially across southwestern MN. Any sensitive groups should begin to monitor their local air quality.

- Precipitation is very unlikely (less than 20%) through Sunday. Isolated to scattered shower and storm chances return Sunday evening and night, but confidence is low on details.

UPDATE

Issued at 408 AM CDT Sat Jul 18 2026

Taking a look across the area, the focus continues to be on the wildfire smoke this morning. In the wake of this morning's surface cold front, it seems like some higher smoke concentrations are being pulled down to the surface leading to slight visibility reductions being observing across parts of the area. While this has mostly affecting our higher elevation areas north of I-90, could see additional visibility reductions along and east of I-29 throughout the day. With the air quality index (AQI) citing moderate to unhealthy concentrations of smoke, make sure to pay attention to your local forecast especially if you're apart of a sensitive group. Otherwise, its gonna be a nice summer day with highs mainly in the mid 80s to mid 90s. Surface winds will remain mostly light and turn to the northeast behind the previously mentioned front. Lastly, could see a few scattered showers to isolated thunderstorms develop along and south of the Highway-20 corridor this afternoon with the southward propagating front. While severe weather is not expected, an occasional stroke of lightning and pockets of moderate to heavy rainfall will be possible IF things can develop.

DISCUSSION

Issued at 1251 PM CDT Fri Jul 17 2026

A weak cool front will sag south tonight into Saturday. Moisture and forcing along this boundary are very weak, so showers and storms are very unlikely. Parts of northwest IA late this afternoon could see a spotty shower or storm as a few of the models indicate a weakening cap, but with no shear and about 500 J/kg of skinny CAPE, brief heavy rain should be the only concern.

Otherwise Saturday should see a bit of a reprieve from the heat for many with highs expected to range from the mid 80s in southwest MN to the mid 90s along the Missouri River. One concern on Saturday will be the potential for some surface based smoke from the fires across northern MN. With winds turning north and then northeast, some of this could leak into the area. For now smoke concentration look to remain fairly low.

Sunday will see a return of southerly flow and hotter conditions as upper level ridging builds ahead of a strengthening jet along the Canadian border near MT. Still some hints of elevated moisture and very weak instability late Saturday night into Sunday morning which could lead to isolated showers and a very isolated thunderstorm. However, the latest model runs are drier aloft than previous runs, so confidence in this is waning. Otherwise, may need a heat advisory for areas near and west of I-29 Sunday afternoon and evening with heat indices likely above 100. Sunday night will see fairly strong southerly flow in place which will lead to very warm lows in the 70s.

Monday still has a few question marks on heat, but for areas near and south of I-90 there will again be a very good chance for heat indices of 100 or greater. This is due to that jet max to the northwest now diving southeast into the area and dragging some cooler air south. For now coverage of any showers and thunderstorms looks isolated to scattered with the better chances Sunday night into Monday evening. Frontal timing and mid level moisture will play a bog role on coverage.

Once this front sags south Monday evening, stronger northwest flow aloft will remain in place which will bring temperatures back to normal or a bit below normal for the remainder of the week. While there will likely be a couple of weaker waves during this time confidence on anything more than isolated is low.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 625 AM CDT Sat Jul 18 2026

Mostly VFR conditions with occasional MVFR vsby are expected today. The main focus continues to be on the wildfire smoke which as promoted temporary MVFR vsbys to areas along and east of I-29. While this will likely persist intermittently through Sunday as the plume sits overhead, not expecting many other impacts. Otherwise, northeasterly winds will persist for the most of the day to end the TAF period.

FSD WATCHES/WARNINGS/ADVISORIES

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