textproduct: Sioux Falls

KEY MESSAGES

- Scattered showers and thunderstorms are expected this afternoon into the evening over northeast NE and northwest IA. There is a very small risk for severe storms, with the main threats quarter sized hail, wind gusts to 60 mph, and locally heavy rain.

- Severe weather possible on Friday afternoon and evening. Confidence is low due to the potential for a stronger cap.

- Additional very good chances (50-80 percent) for showers and thunderstorms return on Sunday.

- Cooler conditions arrive this weekend into early next week.

DISCUSSION

Issued at 111 PM CDT Tue Sep 8 2026

The right entrance region of the upper level jet will move across the area this evening, helping increase convergence along the low to mid level boundary. Much drier air was filtering in behind the surface front, with 30 and 40 degree dew points in central SD. With 1500-2000 J/kg CAPE ahead of this front and about 40 knots of deeper layer shear, a few stronger updrafts will be possible later this afternoon. For now the better chances appear to be from northeast NE towards Storm Lake and points south. The main severe threat should exit the area by early evening as cooler and drier air settles in behind the exiting right entrance region.

Wednesday should prove to be a pleasant day with decreased humidity and seasonally warm temperatures in the upper 70s to lower 80s. Northwest winds may gust as high as 25 mph, with lighter winds across northwest IA. High pressure at the surface will drift across the area tonight and allow for some cool morning lows, mainly low to mid 50s but a few lower spots could see lows as cool as the upper 40s.

Upper level troughing digs across the Northern Rockies Thursday which will swing lower level winds around to the south, allowing for slightly warmer temperatures, generally lower to mid 80s.

As this upper level trough spreads onto the Plains Friday, an environment that potentially supports severe weather will set up. The challenge that day will be breaking the cap. If the cap can be broken, 2000-3000 J/kg CAPE along with about 30-40 knots of deep layer shear would support a few severe updrafts.

Once this front moves through Friday night, much cooler air will settle into the region. Highs Saturday through Monday will likely be in the 70s, with some 60s possible on Sunday. Lows each morning should be roughly 45 to 55.

Sunday into Sunday night will see another fairly strong trough move through which increases warm air advection and should bring fairly widespread showers and thunderstorms. For now any sever weather looks to remain very isolated.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1230 PM CDT Tue Sep 8 2026

A front will drift southeast through the area this afternoon into the evening. Some brief MVFR ceilings will be possible near this front. Otherwise scattered showers and thunderstorms will move through parts of northeast NE and northwest IA through early evening. An isolated storm could become severe. Otherwise mainly VFR conditions are expected. Some patchy fog in northwest IA will be possible late tonight into Wednesday morning.

FSD WATCHES/WARNINGS/ADVISORIES

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