textproduct: Sioux Falls

KEY MESSAGES

- Patchy fog will impact areas near and west of I-29 early this morning, especially in areas which received more substantial recent rainfall. Any fog should burn off by mid-morning.

- Dry conditions and seasonable temperatures will prevail through the weekend.

- Shower and storm chances return Monday night into Wednesday. An isolated strong to severe storm is possible in portions of southeast South Dakota Monday evening, if storms can develop.

UPDATE

Issued at 405 AM CDT Sat Aug 1 2026

Seeing patchy fog developing via satellite and surface obs, mainly west through north of Sioux Falls where more substantial rainfall was reported over the past 24-36 hours. At this time, dense fog is not expected to become widespread enough to warrant any headlines.

Otherwise no significant forecast changes early this morning. A Level 1 of 5 risk for severe storms was introduced in the Day 3 outlook, mainly for Monday evening as a cold front pushes into southeast SD. If storms can develop along the boundary, there may be enough overlap between instability ahead of the front and greater wind shear behind to support an isolated strong to severe storm. Confidence remains low at this time, though, so if you have outdoor plans Monday evening, continue to monitor the forecast for the latest updates.

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 /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 635 AM CDT Sat Aug 1 2026

Patchy fog producing sporadic MVFR-locally IFR visibility as we start this TAF period, though not directly impacting TAF sites at this time. Conditions should quickly improve to VFR by 14Z.

North winds increase slightly through the morning, most notably along/east of I-29 were occasional gusts 15-20kt are expected through the afternoon. Any gusts quickly diminish by sunset with light/variable winds becoming light south into Sunday morning.

FSD WATCHES/WARNINGS/ADVISORIES

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