textproduct: Sioux Falls

KEY MESSAGES

- Warm and humid conditions continue this afternoon. Afternoon heat indices have warmed to the 80s, 90s, with a few locations touching 100F. Drink plenty of water this afternoon!

- Low chances (<= 25%) for rain will persist through the rest of today and Monday. Chances for rain increase up to a 50-80% chance for Tuesday. Severe storms could accompany this chance for rain though details remain uncertain. Please continue to monitor the latest forecast.

- Near to above normal temperatures look to continue through the entirety of this week. Chances (20-40%) are possible on Wednesday and Thursday before decreasing for the rest of the week.

DISCUSSION

Issued at 231 PM CDT Sun Aug 30 2026

Hot and humid conditions continue this afternoon as high temperatures have warmed to the 80s and 90s with dew points in the 60s and 70s. This is resulting in heat indices up to upper 80s and 90s with a few locations touching 100F. A shortwave trough continues to take on a negative tilt over eastern Montana/western North Dakota. This will keep the majority of strong to severe storms in this area. This wave will also be responsible for a cold front that remains on track to push into the forecast area late tonight. Latest hi-res guidance shows little to no rain developing along this boundary due to large capping in place ahead of the boundary. At the same time, cloud cover will increase aloft. Despite the front pushing through the area, low temperatures look to stay quite warm overnight with lows only falling to the 60s and 70s. In fact, some locations will come within 3 degrees of their record warm lows. With dew points remaining in the 60s overnight, tonight will continue the muggy conditions we have experienced this weekend.

Monday will be similar to the weekend though a touch cooler as the thermal ridge gets pushed off to the south and east thanks to the previously mentioned front. That said, high temperatures still look to remain in the 80s to potentially reaching 90F in a few locations. The previously mentioned cold front will fully push through the forecast area by Monday afternoon, resulting in most likely another dry and hot day. Dew points will lower to the 50s and 60s, keeping humidity values lower than what we saw this weekend. If rain were to develop along the front, thunderstorms may be possible though this is unlikely (<= 10% chance) to happen. Low temperatures will remain warm though a bit cooler than Sunday's lows, with temperatures bottoming out in the 60s.

A shortwave trough will eject out from the Rockies and into the Northern Plains on Tuesday. The mass response from this wave will return the previously mentioned front northwards, but this time as a warm front. Latest guidance still varies on how far north this front will return. A few of the hi-res models show the front returning well into the forecast area. But the ensembles as well as the machine learning (ML) guidance keeps the front just south of highway- 20 down to around I-80. Tough to say how far north the front will return but the ensembles continue to show moderate to high probabilities (50-80%) for rainfall amounts to exceed a tenth of an inch of rain across the area, signaling at least elevated showers and storms are on the table north of the front. Instability values will also depend on where the front sets up. Thus, severe weather remains possible as supported by the latest ML guidance showing a 5- 15% chance for strong to severe storms.

Chances (20-40%) for rain will remain in the forecast for the rest of the week and next weekend. The highest probabilities look to come on Wednesday and Thursday as a more active pattern continues aloft. Medium range guidance is becoming more consistent with upper level ridging building over the central CONUS towards the end of next week and next weekend. This would result in warmer temperatures, potentially back into the 90s, and most likely drier conditions. In fact, this pattern is shaping up to be an omega block pattern. Pattern recognition and forecast experience suggests that this pattern may retrograde west over the coming days. The ensembles are also in favor of this as their trends have already been amplifying the ridge as well as pushing the ridge axis further west as well. Surface features are more uncertain, so questions remain regarding surface moisture and resulting humidity. Will be keeping an eye on how this pattern evolves over the course of the week.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 642 PM CDT Sun Aug 30 2026

VFR conditions expected through the period. Can't rule out some low stratus developing behind a cool front around daybreak, but chances for this are low (<=20%). This eastward moving front will turn southwesterly winds to the north-northeast late tonight through early tomorrow morning. There looks to be a slight uptick in winds immediately following the frontal passage in south-central South Dakota, but will likely see sustained winds only pick up to around 10-15 kts during that time. Though a few showers are possible ahead of the front, thunderstorms look unlikely through the period.

FSD WATCHES/WARNINGS/ADVISORIES

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