textproduct: Sioux Falls

KEY MESSAGES

- Additional periods of scattered showers and non-severe, isolated thunderstorms continue into this evening - mainly south of Interstate 90. Severe weather is not expected.

- Milder temperatures through Wednesday with above normal temperatures Friday into the weekend. Although details are uncertain, rain chances may return to the region this weekend.

UPDATE

Issued at 347 AM CDT Tue Aug 4 2026

Showers and elevated storms continue to move east this morning across northwestern IA into the MO River Valley. Severe weather risk is very low. Stronger storms may produce wind gusts to 50 mph and/or dime size hail through 5 AM. Storms have been very pulsy in nature, likely due to decreasing shear and instability. Still expect showers and very isolated storms to linger through today and into tonight as the front stalls then sinks slowly south. Severe weather is not expected. Rain should end by late Tuesday night along the US Hwy 20 corridor.

Northerly flow, clouds, and CAA keep temperatures today and tomorrow cooler than average. Increased sky cover from the NBM to account for thicker concentrations of wildfire smoke aloft through Wednesday evening. May see some surface smoke as well, so maintained mention as those who are very sensitive to the smoke may feel impacts. Do not expect impacts to visibility.

DISCUSSION

Issued at 130 PM CDT Mon Aug 3 2026

Elevated, post frontal thunderstorms are expected to develop around the James River Valley later this evening. Timing appears to support the better chances from about 9 pm to midnight for any stronger updrafts. Assuming the models are correct with the moisture around 800-700mb behind the front, about 1000-1500 J/kg CAPE is expected with about 30-40 knots of effective shear. This may support hail to the size of quarters and with DCAPE about 1000-1500 J/kg some stronger gusts of 65 to 70 mph are possible. Of note is that the freezing level is around 14000 feet which will limit the hail threat a bit.

Tuesday will see some mid level moisture and weak elevated instability linger, which should drive scattered showers throughout the day. The better chances will be south of I-90. Amounts will not be very high, but a few locations should get 0.10" to 0.25". The widespread cloud cover and scattered showers will limit temperatures as well, with highs generally in the mid 70s.

Another wave will move by on Wednesday, with more cloud cover and rain chances near and south of roughly the Missouri River. With cloud cover and somewhat cooler low to mid level temperatures highs will again be below normal, ranging from 75 to 80 near and north of I-90 to the mid 70s south.

A warming trend will set up for the weekend as west northwest flow aloft becomes more westerly. Temperatures should climb into9 the 80s on Thursday, then mid 80s to lower 90s Friday and Saturday with some question marks for Sunday as a wave could bring slightly cooler conditions. While there is no rain in the forecast during this time, each of the models generates weak waves, with little to no agreement on when. So, as the weekend approaches, there may be a couple of brief periods when showers and thunderstorms develop.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 621 AM CDT Tue Aug 4 2026

Most of the area remains at VFR conditions, with some MVFR stratus across northwestern IA. Additional MVFR conditions are possible along and south of I-90, where periodic showers and isolated thunderstorms are expected into tonight. Left mention of SHRA out of KFSD for now with lower confidence in coverage. Additionally, confidence in timing at KSUX is low regarding precipitation later in the period as guidance remains quite varied in location of convection.

Winds become light and variable toward the latter half of the period.

FSD WATCHES/WARNINGS/ADVISORIES

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