textproduct: Sioux Falls

KEY MESSAGES

- Showers and storms should be a bit more widespread tonight (50-70%). Locally heavy rain and isolated severe storms are possible. Coverage and intensity have been trending down a bit however.

- Monday evening and night could see an isolated severe storm, with the better chances in central SD and also near highway 14.

- Otherwise most days through next week will see highs in the 80s and lows in the upper 50s to mid 60s.

DISCUSSION

Issued at 237 PM CDT Sun Aug 23 2026

A pair of waves are affecting the area, or nearby, today. The first is moving southeast through Nebraska and is keeping any instability to the south and west bottled up. Model soundings not hinting at a whole lot of activity this afternoon, with a fairly dry and stable air mass in place.

Tonight a second wave will pass by to the north and will swing a little bit of mid level moisture into the area. As this moisture moves in, some weak elevated instability, likely 500-750 J/kg CAPE develops. This will support some scattered shower and isolated thunderstorm activity, but for now severe weather looks unlikely. A few pockets of heavier rain are also possible, but also trending downward.

Monday will see temperatures warm a bit with humidity likely to increase as well. This is in response to strengthening southerly flow as a stronger wave moves east along the Canadian border. This will increase instability, especially to the northwest of the area, and should bring scattered thunderstorms to parts of central SD and near the highway 14 corridor. With the potential for about 1000-1500 J/kg CAPE and decent unidirectional shear, and isolated severe storm will be possible in these locations. One area to watch will be near northwest IA late Monday afternoon and evening where there are some hints the cap could weaken a bit as elevated moisture advection bring some instability to that area. Low confidence, but something to monitor.

Northwest flow aloft Tuesday into the weekend will keep seasonally warm temperatures in place with highs in the 80s and lows from the upper 50s to mid 60s. Starting to see a little more consistency on the next better chance for showers and thunderstorms on Friday. The latest Canadian, GEFS and EC ensembles all indicate about a 30-5- percent chance for a tenth of an inch or more of precipitation.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 647 PM CDT Sun Aug 23 2026

Scattered showers and storms look to develop late tonight, favoring areas near and south of I-90 through daybreak Monday. Confidence remains fairly low as to whether or not this activity hits KFSD and KSUX or remains just south and west of the sites, but still kept the PROB30 groups with some adjustments to timing, notably a later possible arrival time for KSUX.

Winds will generally remain southeasterly through the period while staying moderately breezy. Winds will be sustained around 8-12 kts through the period with occasional gusts to around 20 kts this evening and again during the day Monday.

FSD WATCHES/WARNINGS/ADVISORIES

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