textproduct: Sioux Falls

KEY MESSAGES

- Areas of fog are once again likely tonight into Sunday morning. Dense fog is a little less likely.

- The next better chance for rain will come Sunday night into Monday. Thunderstorms will be very isolated and severe weather is not expected.

- Below normal temperatures will persist through next week.

DISCUSSION

Issued at 1247 PM CDT Sat Sep 19 2026

The low levels remain saturated to near saturated tonight into Sunday morning which will keep the potential for fog in place, as well as patchy drizzle. Dense fog will again be fairly sparse, but some locations will see the visibility fall to a half mile or less at times.

Overall, Sunday looks to be a pretty dreary day with low level saturation deepening through the day. While the visibilities will likely improve a bit through the morning, stratus will remain fairly low and will not dissipate. As this low level moisture deepens, a weak wave will approach from the south and bring slightly cooler temperatures aloft and a bit more elevated moisture. This should allow for scattered showers to develop, but with only very weak instability thunder looks unlikely. As this wave rotates northward, a slightly stronger wave will move eastward through northern NE into northwest IA which should keep an expanding area of rain in place across the area. Given the placement of the upper level wave and the associated instability, parts of south central and southeast SD down the Missouri River will likely see the better chances for an inch or so of rain. The 12z Nam, RRFS and HRRR all paint these higher rainfall amounts near and south of I-90.

This wave slowly moves through on Monday, so expect to see showers slowly dissipate from west to east through late afternoon. Stratus will once again be difficult to shake as the push behind this wave is pretty weak and lighter northeast to east flow will be in place in the lower levels. Some hints in the soundings that clearing will be possible on Monday night, but with light winds and a moist boundary layer, fog will then become moire likely for late Monday night into Tuesday morning.

Tuesday and Wednesday will see some weak upper level ridging with afternoon temperatures likely only rising into the 60s.

Wednesday night into Thursday a trough of low pressure will approach from the west and bring a chance for showers and isolated thunderstorms. Severe weather looks unlikely. For now the better chances will likely be west of I-29.

Temperatures should remain a touch below normal Thursday into Friday with some potential for spotty showers. Highs generally in the upper 60s to lower 70s.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 647 PM CDT Sat Sep 19 2026

MVFR to IFR stratus will continue to impact the area through most of the period. Under the stratus will be some light fog in spots along with patchy drizzle through tomorrow morning. Locally LIFR cigs will be possible late tonight into tomorrow morning, though confidence was not high enough to include in the TAFs at this time. Scattered shower chances will increase through the daytime hours Sunday, but thunder still looks quite unlikely. Winds will be mainly out of the northeast through the period. Strongest winds will generally be during the daytime hours Sunday where occasional gusts to around 20 kts is possible.

FSD WATCHES/WARNINGS/ADVISORIES

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