textproduct: Sioux Falls

KEY MESSAGES

- Above normal temperatures continue through the rest of this week and into the weekend, with humidity increasing daily. However, we'll remain below heat advisory levels.

- Severe weather risks develop after midnight bringing pockets of strong winds and severe hail into Wednesday morning. Some uncertainty lingers on coverage of strongest storms.

- An unsettled pattern continues into the holiday weekend with nearly daily risks for convection focused in the evening and overnight hours.

- Beyond Wednesday's evening isolated to scattered severe risks, concerns are growing for more widespread severe storms Thursday evening into Friday and again Friday into Saturday with one or more overnight storm complexes possible.

DISCUSSION

Issued at 1247 PM CDT Tue Jun 30 2026

THIS AFTERNOON/EVENING: Overnight storms have driven drier air southeast into the CWA this afternoon, both at the surface but also aloft. Richer low-lvl theta-e airmass isn't too far away though focused along Highway 20 into portions of southwestern Nebraska. Therefore expect a continuation of quiet conditions, but still above normal temperatures into this evening. One thing to note today is the arrival of wildfire smoke through the region. This smoke layer is producing a milky sky, but also some minor downward mixing of smoke to the surface creating air quality impacts.

TONIGHT: Short term guidance continues to show a shortwave ejecting out of the Central Rockies later this evening. The approach of this wave will do two things. Firstly inducing a 40+ knot LLJ through the Plains which will begin the northward advancement of richer and more unstable air into the CWA after midnight. Secondly, inducing convection across southwestern and southern Nebraska by mid-evening. The approach of this wave will push convection northward into the MO River valley after midnight, with additional scattered convection forming on the advancing elevated warm front further east into Iowa. Soundings do show an increase in MUCAPE towards the 2000 J/KG mark ahead of this wave. Anticipating some stronger wind gusts forming with convection as it crosses Nebraska later this evening and any new updraft on the leading edge of advancing low-lvl moisture could produce some severe hail. The uncertainty tonight is just how focused any stronger cluster development could become. Latest HREF 2-5km updraft helicity plots suggest that at least a narrow corridor through SE South Dakota into portions of the Tri-State area could see some higher severe weather potential as mid-lvl flow turns parallel to storm movement. That said, would expect fairly widespread 30 to 50 mph wind gusts into the James River valley, with potential for a more localized pocket or more intense gusts that approach 70 mph with hail. The storm risk will continue through 12Z into SW Minnesota where we'll need to watch redeveloping updrafts try to form on the veering LLJ.

WEDNESDAY: Morning convection could do one of two things. Completely dissipate with the passage of the mid-lvl shortwave, or fester deeper into the morning hours as the LLJ continues to converge into SW Minnesota. Lingering convection could continue a low end hail risk. A more likely scenario is that we see some stabilization behind the departing wave with an EML beginning to build in by early afternoon. Guidance has backed off slightly on the potential for widespread redevelopment in the afternoon and evening. This is likely due to a lack of a strong lifting mechanism, continued lingering EML into the evening, and departure of mid-lvl jet. The nearby presence of mid-lvl vorticity across central and northern South Dakota and potential of left over boundary from morning convection, and then redevelopment of the evening LLJ will force at least a 20-40% POP for convection by the evening into the overnight hours mostly along and east of I-29 and north of Highway 14. Given instability and presence of sufficient remaining effective shear, isolated to scattered supercells could be possible, potentially merging into one or more eastward progressing clusters in the late evening. This would be favored over portions of southern Minnesota. Greatest concerns would be 2" hail but with significant mid-lvl dry air and steep 0-2km lapse rates strong winds would also be likely.

THURSDAY-FRIDAY: We'll stay in a highly unstable environment for the end of the week and into the upcoming holiday weekend the combination of the SERN ridge and western CONUS trough keeps southwest to quasi-zonal flow through the Plains. This pattern is one that will keep temperatures above normal, but also allow dew points to remain in the upper 60s to lower 70s. The combination will allow moderate to high instability to build each afternoon and continue into the overnight. By Thursday afternoon, we'll be keeping an eye on the development of a stationary front lifting northward as a warm front in the afternoon and evening. While and EML will be in place, any subtle wave could trigger isolated to scattered strong convection in the Tri-state area. Greater confidence however in the development of severe convection on the western High Plains and Black Hills region in the afternoon that would translate east as a strong to severe forward propagating high wind potential MCS into Friday morning.

We'll need to see how things play out Thursday into Friday to have a strong handle on the severe potential that may develop Friday evening and overnight. Some guidance this morning hints at the overnight MCS laying out a strong outflow boundary that could serve as a focus for renewed severe convection Friday evening and overnight.

4th of July: Confidence lowers each day given the uncertainty in the convective development the previous days. That said, the overall synoptic pattern remains problematic as a stationary boundary linger in the area and the flattened mid-lvl flow brings increased potential for daily shortwave activity eastward into the Plains. Temperatures remain near to above normal with humid, but not oppressive conditions favored. Bottom line is anyone with outdoor plans the 3rd and 4th needs to be aware of the forecast and the storm potential that may develop. Additionally, with the potential for multiple MCS, there may be some concerns for excessive rainfall in areas that see repeated convection. Continue to monitor this risk.

SUNDAY-MONDAY: The synoptic pattern shifts by Sunday into next week as mid-lvl ridging builds through the Plains. NBM probabilistic data would suggest a fairly normal 25/75th spread for high temperatures from the mid 80s to the lower 90s into early next week.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1216 PM CDT Tue Jun 30 2026

VFR conditions continue into the evening hours. Eventually thunderstorms over central Nebraska and western Iowa will spread an overcast mid-lvl cloud deck northward. This convection will spread northeast overnight impacting any one location for 1-3 hours. Strong wind gusts may be possible, but confidence is low on how high those gusts may be.

Once this convection passes, VFR conditions return with a light and variable surface wind.

FSD WATCHES/WARNINGS/ADVISORIES

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