textproduct: Sioux Falls

KEY MESSAGES

- Gusty winds will become light to calm overnight. Areas along and west of I-29 are most likely to become calm and may allow for patchy fog formation early Saturday morning along water ways and low areas. Any fog should burn off by mid-morning.

- Dry conditions and seasonable temperatures return for the weekend. For next week, shower and storms chances will return Monday night into Tuesday.

UPDATE

Issued at 837 PM CDT Fri Jul 31 2026

The forecast remains on track for the next 48 hours. Saturday early morning winds will be light, but it is uncertain if they will become light enough for fog to form. If it does, it will be patchy in nature and most likely confined to water ways and low laying areas. Any fog should burn off by mid-morning. Northerly winds will increase after sunrise and become slightly breezy gusting to 15-20 mph. Skies will be mostly free of clouds, however a milky haze will be present due to wildfire smoke. Highs will be on the low side of average in the mid 70s and low 80s due in part to weak CAA and the smoke to a lesser extent.

Overnight Sunday winds will become light and turn to the south- southeast as surface high pressure passes through the region from northwest to southeast. Southerly winds usher in warmer and moist air. Dew points will climb in to the upper 60s to low 70s. Slightly warmer highs thanks to the WAA will be in the upper 70s to mid 80s. The highest dew points and warmest temperatures will be offset, and so Heat Index values will be near to slightly warmer than the forecasted highs. Skies will once again be mostly clear but obscured somewhat by smoke. Overnight Sunday into Monday morning a subtle mid- level short wave and a strengthening LLJ may induce isolated showers and weak thunderstorms for areas along and north of Highway 14. A very dry subcloud layer will likely prevent most rain from reaching the ground, therefore we are not expecting much if any accumulation.

Monday's highs will be slightly warmer in the low 80s to low 90s over south central South Dakota. A cold front will move through from west to east late Monday afternoon into Tuesday bringing the next chances for showers and thunderstorms. At this time storms do not look to become severe, however there is also high uncertainty. We will monitor the trends over the next days. What follows for the remainder of the week looks to be a somewhat active pattern with multiple chances for showers and thunderstorms.

DISCUSSION

Issued at 247 PM CDT Fri Jul 31 2026

A nearly stacked low pressure system will continue to drift southeastward into central Iowa through the remainder of the afternoon, and with the surface low deepening, look for winds to increase a bit more mainly east of I-29 through the early evening hours. Most spots top out with wind gusts between 35 and 40 mph, but isolated pockets of gusts to around 45 mph will be possible over northwest Iowa through about 7 to 8 pm this evening. This should remain in short duration and isolated and so decided against wind headlines. Moisture also continues to wrap around this low which will keep mainly light rain in the forecast through this evening primarily east of I-29. Soundings show a little bit of elevated instability over parts of northwest Iowa, so can't rule out a rumble of thunder this afternoon, but chances for this are looking less and less likely. The last of the showers should exit northwest Iowa by 10 pm to midnight tonight, leading to dry conditions heading into the weekend.

Patchy fog is possible where winds can go very light to calm by early tomorrow morning, but it does look like winds should remain elevated enough to prevent widespread development. Trends will be monitored. Otherwise, a pleasant day is in store for tomorrow with highs in the upper 70s to lower 80s with dew points down into the mid 50s west to low 60s east. These lower dew points will lead to more comfortable conditions out there especially when compared to the past few days. The humidity relief will be short-lived however, as southerly flow returns on Sunday and allows dew points to rise through the 60s and potentially as high as the lower 70s in the afternoon. It won't be nearly as hot as it has been though as highs will still remain mainly in the 80s with a few pockets of highs near 90 in south-central South Dakota. Those hotter areas will likely be offset from the higher dew points though, so heat indices won't get too high. Temperatures will continue to warm on Monday and this will be out ahead of our next cold frontal passage. This cold front may bring a chance of stronger thunderstorms to the area, but the overnight timing of the frontal passage and the fact the better upper level support will be displaced to our north leads to a low confidence forecast for severe weather.

This frontal boundary may stall out or slow down near or south of the Highway 20 corridor as a large upper wave pivots slowly across the region. This will keep rain and storm chances in the forecast mainly south of I-90 through the day on Tuesday and potentially into Wednesday as well depending on where the frontal boundary stalls. Will have to watch this for perhaps some heavy rain potential as some of the lower resolution global models such as the 31.12Z ECMWF and Canadian model 48 hour QPF already shows a stripe of 1 to 3+ inches either near Highway 20 or near I-80 depending on the model. So we'll see what the higher resolution models come up with as we get closer, but these areas south of I-90 didn't receive as much rain with this most recent system, so the flood threat may still remain low anyway. Cooler weather immediately follows the cold frontal passage, with highs likely only staying in the 70s Tuesday and Wednesday before gradually warming up through the end of next week.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 1224 AM CDT Sat Aug 1 2026

VFR conditions are expected to prevail for the period. Winds are expected to be light to calm overnight. Some areas of patchy fog are possible along water ways and low areas, mostly west of I-29 where winds will be lowest. Confidence in winds going calm at any of the TAF sites is low, therefore left mention of fog out at this time. Any fog that does form will burn off by mid-Saturday morning.

After sunrise winds begin to increase ahead of an approaching surface trough axis. Gusts 15-20 kts are possible with the highest winds over northwest Iowa. The trough will push a surface high pressure to the east through the day. Winds will gradually become southerly through the afternoon and evening before becoming light and variable again Saturday night.

FSD WATCHES/WARNINGS/ADVISORIES

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