textproduct: Sioux Falls

KEY MESSAGES

- Areas of fog will lead to varying visibility through the morning commute, perhaps below a mile at times. Fog will be more likely near rivers/ponds and other low-lying areas.

- Warmer and more humid air returns Friday through the weekend with moderate (40-60%) chances for storms by later Friday evening into Friday night.

- Periodic shower and storm chances continue this weekend into early next week. Confidence on any details is low.

- Temperatures will be above normal this weekend into the middle of next week. Highs likely in the 90s Saturday and possibly Sunday.

UPDATE

Issued at 410 AM CDT Thu Aug 27 2026

As temperatures dip into the mid 50s early this morning, we are seeing areas of fog around the area per satellite, airport obs and web cams. Do not expect widespread dense fog, but variable conditions with localized visibility below a mile are possible through the morning commute.

The remainder of the forecast is on track, with the main question revolving around the timing of potential storms Friday into Friday night. As mentioned in the latest SPC Day 2 outlook, potential for development during the afternoon to early evening looks to be on the lower side given decent capping inversion, though depending on timing of a lead mid-level wave, isolated development is not out of the question. Better overall storm chances may wait until later in the evening and overnight, as the low level jet ramps up and interacts with a trailing portion of the mid-level wave. In either case, shear and instability appear sufficient for isolated severe storms with large hail the primary threat given less favorable DCAPE values.

DISCUSSION

Issued at 108 PM CDT Wed Aug 26 2026

Surface high pressure remains in place through Thursday resulting in quiet weather across the area. Lows in the 50s tonight with highs on Thursday in the lower to mid 80s.

Elevated moisture moves in around the 700-800 mb layer late Thursday night into Friday morning. This could result in spotty showers and isolated thunderstorms. Shear is weak and CAPE values running about 500-1000 J/kg. Very dependent upon this small layer of moisture however, so confidence is low for now.

Southerly flow become established at the surface on Friday with gusts around 25 to 30 mph likely. With south to southeast flow at the surface any instability that develops through the day will likely remain capped, however with some potential for a wave to move through on Friday afternoon this capping could weaken and allow a few thunderstorms to develop. With moderate shear and 1000-1500 J/kg CAPE, an isolated severe storm will be possible. A secondary wave and slightly deeper instability on Friday night may lead to additional shower and thunderstorm chances with additional severe weather threats.

Temperatures warm across the area on Saturday as the wave moves by to the north. Even with stronger west southwest flow aloft and decent mid level warm advection, weak mid to upper level ridging should suppress any convective activity. Highs should climb into the 90s near and west of I-90.

Sunday may be a day to keep an eye on we a wave tracks by along the Canadian border and a weaker sub tropical like wave drifts northeast into the area. With another day expected to climb into the 90s and some weak forcing aloft, we could see a few storms develop. For now confidence is too low to include in the forecast.

Southwest flow aloft remains in place through the middle of next week and the next wave of interest has some agreement and may arrive Monday night into Tuesday. Otherwise temperatures will remain above normal Monday int Wednesday.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 629 AM CDT Thu Aug 27 2026

Valley fog is resulting in areas of IFR-LIFR visibility as we start this period, though impacts at TAF sites are minimal. After the fog dissipates, which is expected by 13Z-14Z, VFR conditions will prevail through tonight with variable winds under 10kt.

FSD WATCHES/WARNINGS/ADVISORIES

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