textproduct: Sioux Falls

KEY MESSAGES

- Scattered showers and thunderstorms will continue through mid-Tuesday morning.

- Warm and humid today with highs in the 80s and 90s. Heat index values will climb into the mid to upper 90s. While no headlines are anticipated at this time, proper hydration and breaks out of the sun remain essential.

- An active pattern continues with chances for strong to severe thunderstorms nearly every evening/overnight for the rest of the week. Details remain uncertain as storms will depend on how the previous day's storms evolved.

UPDATE

Issued at 421 AM CDT Tue Jun 30 2026

Another round of strong to severe thunderstorms are ongoing as of 4:00 am CDT. These are the result of a mid-level wave moving through the region overnight. Increasing mid-level lapse rates ahead of the wave in an already strongly unstable environment coupled with deep layer shear of 40-50 kts result in an environment capable of producing very strong wind gusts of 70-80 mph and heavy rainfall. Large hail to the size of a ping-pong ball is also possible. Area most at risk is along and east of I-29. Storms are expected to continue through daybreak.

Tuesday should be a mostly sunny, lightly breezy day with highs in the mid 80s to mid 90s. Dew point temperatures will be in the 50s for southeast South Dakota and southwest Minnesota, and in the mid 60s to low 70s in northeast Nebraska and northwest Iowa. Apparent temperatures will once again be warm in the low to mid 90s for most of the region, but in the mid to upper 90s in northwest Iowa. Not high enough or widespread enough to need a Heat Advisory, but still enough that proper hydration and breaks out of the heat will be necessary.

Throughout the day moisture rich air will flow north and pool along a stationary front draped from south central Nebraska northeast into the Arrowhead of northeast Minnesota. Steep mid-level lapse rates, 2000-3000 J/kg of MUCAPE, and 30-40 kts of deep layer shear will work together to result in another environment capable of producing strong to severe thunderstorms. SPC Day 1 Outlook includes a Marginal Risk (level 1 of 5) for our CWA Tuesday evening into the overnight. Similar to the past couple of days, a strong cap will be in place. However, as the LLJ begins to ramp up in the mid to late evening a few discrete super cells are possible in northeastern Nebraska. With initial storm development large hail up to 1 to 1.5 inches are possible. One thing to note, the freezing level is greater than 13,000 ft AGL. This may have an impact on hail size, as it will have plenty of time to melt on the way down. Heavy rain and damaging wind gusts are also possible. Storms are expected to become elevated as they quickly grow upscale into a QLCS, possibly with bowing segments. At this point the threats will transition to wind, with 70 mph gusts possible. Storms will progress northeast through the overnight into southwest Minnesota where they may linger through about mid-day.

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 /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 542 AM CDT Tue Jun 30 2026

Lingering showers and thunderstorms over northwest Iowa and southwest Minnesota will taper off by mid-morning. Mostly clear skies and VFR conditions will prevail for the majority of the period. Winds will be west-southwest and light. After sunset winds become light and variable.

Chances for showers and thunderstorms return tonight. Storms will push into south central South Dakota from nebraska around midnight and progress northeast through approximately 01.15Z. Storms have the potential to become strong to severe with hail up to 1.5 inches, wind gusts up to 70 mph, and heavy rainfall.

FSD WATCHES/WARNINGS/ADVISORIES

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