textproduct: Sioux Falls

KEY MESSAGES

- Isolated to scattered severe thunderstorms have begun this evening and will continue into the overnight hours. The more concerning threat will possibly come from about 11 pm through 4 am in and near northwest IA where wind gusts to 80 mph, hail to ping pong ball and locally heavy rain will be possible.

- The heat headlines will continue into this evening. After today, the heat index for most of the area should remain below 100 degrees through the week. There may be a few times when heat headlines are needed with the better chances in northwest IA. Moderate to major heat risks are expected however through the week.

- An active pattern this week leads to periodic threats for locally heavy rain and scattered severe storms. At this time the better chances appear to be Tuesday night and Thursday into Thursday night.

UPDATE

Issued at 710 PM CDT Mon Jun 29 2026

As of 7:00 pm CDT, storms have begun to fire along a cold front draped from Niobrara, Nebraska through Sioux Falls into eastern North Dakota and western Minnesota. Storms are expected to move northeast with the front through the next few hours, impacting eastern South Dakota and western Minnesota and Iowa. Storms have the potential to become severe and produce winds up to 80 mph, hail up to the size of ping-pong balls, and brief heavy downpours. Though the risk is low, a tornado or two cannot be ruled out. This first round of storms looks to move out of the region by around 11 pm.

A second round of storms are expected to form as a weak wave pushes northeast out of Nebraska after midnight. Threats will be very similar, very strong damaging wind gusts, large hail, heavy rain, and possibly a tornado. This second round is expected to have the largest impacts along and east of a line from Yankton, to Sioux Falls, to Marshall, Minnesota. This round should be clear of the area around or shortly after 7 am Tuesday.

DISCUSSION

Issued at 108 PM CDT Mon Jun 29 2026

Late this afternoon and Tonight:

An unstable environment will be in place today as a weak front works into areas between about the James River and I-29 this afternoon. This may be a focus for isolated thunderstorms as a weak wave begins to move northeast from Nebraska ahead of the main wave to the west of the area. CAPE values sitting around 3000 J/kg with the 0-3km and 0-6km shear values sitting about 30-40 knots. The questions for the late afternoon and early evening activity will be getting enough convergence to overcome the capping inversion. However, given these parameters and a quick look at the model soundings showing a decent amount of dry air below about 600mb, wind and heavy rain will be the main threats. Wind gusts to 80 mph and locally heavy rain will be the main threats. Hail to half dollar will be a threat as well.

Current thoughts are that there will likely be two areas of convection to watch for. The first will be from roughly 6 pm to 9 pm along the surface front and more driven by day time heating. This will likely be near I-29 and is a bit lower confidence given a strong capping inversion and weak low level convergence. The next, increasingly more likely threat will be tied to a weak wave moving out of Nebraska and an increasing LLJ. The better chances for this will be from about 11 pm to 4 am and this is also when the threat for the highest winds is expected.

Tuesday into Wednesday:

Tuesday should prove to be a fairly nice, albeit very warm, summer day with lighter winds and dew points back into the 50s and 60s and highs from the upper 80s to mid 90s. Currently do not anticipate any heat headlines but parts of northwest Iowa do get close to a 100 heat index so there will be some potential at least.

Model output continues to point to Tuesday night into Wednesday as a period with a good chance for showers and thunderstorms. A wave will rotate northeast through Nebraska and bring a strong increase in the LLJ into southern SD by about 6z and northwest IA and southwest MN shortly after. Given the shear profile and expected instability around 2500 J/kg, a few severe storms will be possible. The low level remain fairly dry so given the amount of instability we may see some potential for 75 to 80 mph winds as well as pin pong ball sized hail.

Wednesday afternoon and evening may see some scattered showers and storms with the better chances in northwest IA as a front lingers after the likely morning showers and storms. With the threat for clouds and a post outflow air mass, heat headlines are again not expected.

Thursday into the weekend:

The next good chance for showers and thunderstorms moves in Thursday into Thursday night as another well agreed upon wave moves through. Will likely continue the threat for locally heavy rain and isolated severe thunderstorms depending upon where any outflow boundaries end up.

Friday into the weekend continues the trends of near daily waves as the upper level flow transitions to a bit more westerly direction. This hints at a chance for showers and storms Friday and Saturday with a potential break by Sunday into Monday as a weak ridge aloft builds in. For now this time frame is pretty low confidence given all of the activity tonight through Thursday night.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 648 PM CDT Mon Jun 29 2026

Showers and thunderstorms have begun to fire in northeast Nebraska along a cold front draped from there through eastern South Dakota and North Dakota. These storms are expected to move northeast and continue to form along the front. KHON does not look to be impacted but KFSD and KSUX could begin to see storms in the next 2-5 hours. Risks include damaging wind gusts up to 70 kts, hail up to a half dollar, and brief heavy downpours. Storms move northeast through the region, and should be out of the region shortly before sunrise.

VFR conditions are expected to prevail through the period except under areas experiencing thunderstorms.

Gusty southerly winds will decrease and become light and variable overnight. After sunrise they will become more westerly but remain light.

FSD WATCHES/WARNINGS/ADVISORIES

SD...Heat Advisory until 9 PM CDT this evening for SDZ039-040- 054>056-060>062-065>070. Extreme Heat Warning until 9 PM CDT this evening for SDZ071. MN...Heat Advisory until 9 PM CDT this evening for MNZ071-072-080- 081-089-090-097-098. IA...Heat Advisory until 9 PM CDT this evening for IAZ001>003. Extreme Heat Warning until 9 PM CDT this evening for IAZ012>014-020>022-031-032. NE...Heat Advisory until 9 PM CDT this evening for NEZ013. Extreme Heat Warning until 9 PM CDT this evening for NEZ014.