textproduct: Sioux Falls

KEY MESSAGES

- For today, heat indices will continue to be near 100 degrees through this afternoon mainly west of I-29, so continue to stay hydrated out there! Also, a pop-up shower or storm is possible near and south of the Missouri River Valley this afternoon, but severe weather is not expected.

- Chances for showers and storms increase Thursday morning, continuing Thursday night into early Friday. Some storms may be strong to severe late Thursday into Thursday night with strong wind gusts to 65 mph and heavy rain the main threats.

- Overall beneficial rainfall is expected Thursday through Friday morning, with a 60-90% probability of at least 0.50 inches and a 30-70% chance of at least an inch for the area. This rainfall could however lead to isolated flash flooding in urban and flood prone areas, so be sure to remain weather aware.

DISCUSSION

Issued at 241 PM CDT Wed Jul 29 2026

Lines of cumulus clouds have developed near and south of the Missouri River Valley this afternoon. Without much upper level support to get storms going, we will need to rely on spots reaching convective temperatures to get storms to initiate. According to soundings, this will be around 95 degrees or so. Chances for storm development with this is low, but either way severe weather is unlikely given weak mid level lapse rates and weak shear. However, can't rule out a wind gust up to 55 mph in any collapsing thunderstorm if they even develop in our area in the first place. Otherwise another very warm and humid afternoon continues, with heat indices pushing 100 degrees at times especially west of I-29 into the Sioux City metro. Doesn't look like these 100 degree heat indices will be too widespread and dew points do look to drop off a bit more through the afternoon, so did continue to hold off on any heat headlines. However, it's still important to be hydrated and take some breaks when working or playing outdoors this afternoon!

Showers and storms over western South Dakota will be knocking on south-central South Dakota's door by daybreak Thursday; however, this activity will likely be weakening as it moves into the area. Additional showers and storms will likely develop as an upper level wave moves across the area and will likely have enough with it to break the cap in the fairly weakly capped environment. This morning activity is unlikely to be severe and should help limit full destabilization from occurring before any afternoon/evening activity develops. However, we will still likely see a line of stronger thunderstorms develop in the afternoon over central South Dakota and move southeastward across the area through the evening hours associated with a cool front. 65 mph winds and quarter sized hail will be the main threat with this afternoon/evening activity.

There is an alternate, but less likely scenario where we don't get much if any rainfall during the Thursday morning time frame due to a stronger than expected cap, allowing for more destabilization to occur. In this scenario, like shown in the 29.12z HRRR, a stronger line/MCS would develop in the afternoon and evening and bring wind gusts potentially up to around 75 mph. Trends will be monitored, so keep up to date with the latest forecast. A secondary wave and an upper level low will close off near the area Thursday night into early Friday morning, likely keeping general showers and thunderstorms continuing into the night. This will also lead to some flash flooding concerns Thursday afternoon into the night. Wet grounds from morning showers/storms will combine with the stronger afternoon storms and overnight storms to lead to some flash flooding concerns mainly in urban areas that see multiple thunderstorms. Rainfall totals through Thursday night/early Friday morning will be around a half an inch to 1.5", but localized amounts exceeding 4+ inches will be possible. Make sure to stay weather aware and keep up to date with the latest forecast!

After this next storm system passes, an upper level ridge will build into the area and help to keep us dry. And with northerly flow in place, high temperatures for Friday and Saturday will be a lot more pleasant with some areas especially on Friday having highs staying only in the 70s! Southerly flow returns again by Sunday, so we should start to see another warm up, though we should stay below heat advisory criteria even as highs warm back up to the middle 80s to lower 90s. The next appreciable rain chances will return Monday night into Tuesday as cold front moves into the area. It looks like there may be enough instability and shear for at least some severe threat, but uncertainty remains high at this time.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 625 PM CDT Wed Jul 29 2026

Latest satellite shows a diurnally driven CU field across the Missouri River Valley early this evening. Am not expecting any new thunderstorm development in this area so should see the CU field dissipate over the next few hours. Thunderstorms across the western part of the state will slowly push eastwards through the evening and overnight hours while on a weakening trend. There remains uncertainty as to whether or not they will survive all the way to the area so have left out any chance for rain in all TAFs. A few models suggest that low level stratus could develop across tomorrow morning. However, this has a low probability (~20%) of occurring so have also left out of all TAFs. Will monitor trends through the rest of the evening and overnight hours.

Another round of showers and storms is expected tomorrow afternoon. Storms look to develop west of I-29 during the afternoon timeframe. These storms will be pushing eastwards to end the period.

FSD WATCHES/WARNINGS/ADVISORIES

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