De Smet, SD 57231 Weather

This Hazardous Weather Outlook is for northwest Iowa, west central Iowa, southwest Minnesota, northeast Nebraska, central South Dakota, east central South Dakota, south central South Dakota and southeast South Dakota.

Day one

Tonight.

Patchy valley fog is possible tonight, mainly east of I-29. Visibility may briefly fall to less than 2 miles at times. Fog should burn off by mid- morning Friday.

Days two through seven

Friday through Wednesday.

Scattered rain and isolated thunderstorms are expected to move into region Friday afternoon. These will continue overnight and taper off Saturday afternoon. Rain totals are expected to be light, a few hundredths to a quarter of an inch. Highest totals expected over northwest Iowa.

Additional chances for accumulating showers the first half of next week.

Spotter information statement

Spotter activation is not expected at this time.

NWS Sioux Falls will discontinue the Hazardous Weather Outlook product (HWO) on November 8, 2026. Weather hazards and outlooks will continue to be provided through other standard NWS products, including weather briefing packets, forecast discussions, weather story graphics, the graphical hazardous weather outlook, and updated hazard messaging. All local products and visual tools are accessible directly at: weather.gov/siouxfalls.

Key messages

- Some very patchy fog is possible late tonight into Friday morning. Mainly along river valleys and east of I-29.

- Showers and very isolated thunderstorms will be possible Friday night into Saturday morning, mainly near and east of Highway 81. Drizzle and spotty showers will be possible west of Highway 81.

- More widespread rain returns later Sunday night into Monday. The EC/GFS and Canadian ensembles suggest about a 40-70 percent for more than an inch of rain.

Update

Issued at 845 PM CDT Thu Oct 29 2026

Broad surface high pressure settles over the southern Great Lakes region overnight. Winds will become southeast around 5-10 mph. This will likely preclude widespread fog formation, but patchy fog is still possible along river valleys and east of I-29 where winds will be lightest. Any fog that does form will quickly mix out after sunrise Friday. Overnight lows are expected to fall to the mid 30s to 40s.

Tonight and through the day Friday a mid-level wave will slowly work northeast into the region. As it approaches stratus will fill in from south to north. This will work to limit highs in the 50s. Prior to the arrival of the main wave periodic, light, WAA driven showers may form along and south of Highway 18 beginning Friday morning. These will be very hit or miss in nature, and areas to the north will likely not see any precipitation during the day. By late Friday afternoon the main wave pushes north into the region. Rain showers will become more numerous and widespread as they move north overnight and through most of the day Saturday. While severe weather is not anticipated, a few hundred Joules of MLCAPE may be enough to produce some lightning. Rain tapers off through the afternoon. There remains disagreement in exact track of the wave, with the GFS taking a more easterly track and the EC, CAN, and NAM a more westerly track. This would impact who sees rain and how much. As of this forecast, the highest totals will be along and south of Highway 18, and may see a tenth to a quarter of an inch. North of there, a few hundredths up to a tenth.

Discussion

Issued at 104 PM CDT Thu Oct 29 2026

Weak ridging aloft moves through the area tonight into Friday. This will allow for an increase in south to southeast flow in the lower levels. Models soundings point towards some possible patchy fog again later tonight, but stratus should increase from south to north late tonight into Friday afternoon. So for now not anticipating widespread fog issues. Other than the increasing stratus through the day, Friday should mostly be dry. By afternoon into the evening a wave will rotate northward bringing slightly cooler temperatures aloft above the increasing low level moisture. This should bring some weak instability with maybe 200-500 J/kg CAPE and no real shear to speak of. This the expectation will be for mainly scattered showers with isolated thunderstorms. The better chances for showers and isolated thunderstorms should be near and east of I-29 with areas near and west of the James River possibly capped and seeing a better chance for drizzle with roughly the lowest 5000 feet saturated and weak lift moving through. For now rainfall amounts look light with some spotty tenth of an inch or so possible.

Saturday the challenge will be trying to break through a fairly deep stratus layer as weak upper level support gradually diminishes. For now expect cloud cover the linger and temperatures to not reach their full potential, likely topping out in the lower 60s in most locations. Still mild for this time of year.

Saturday night into Sunday expecting mainly dry conditions as saturation aloft diminishes and any weak instability is gone. Sunday will likely see a resurgence of stratus ahead of the next wave coming Sunday night into Monday. This should again keep high temperatures mostly in the lower 60s.

Sunday night will see a surge of warm air advection in the lower levels as low pressure deepens to the west southwest and an initial wave races by to the northeast. Would not be at all surprised if we see enough instability Sunday night into Monday morning to produce a few thunderstorms as the band of strong warm advection moves through. After this a few question marks on low pressure development. With the jet still pretty strong and southwest of the main trough, expect low pressure to deepen across KS/NE area, then lift east or northeast into Tuesday. The low pressure movement is fairly low confidence as the models are yet to agree upon how much jet energy wraps around to the east side of the low, but if enough does, we could see rainfall continue well into Tuesday. For now even on the backside of this system it is a bit too warm for snow, so thinking all rain.

If this system were to wrap up as much as the ECMWF suggests, a few snow showers would be possible Wednesday into Thursday, but not a lot of support from other models, so nothing more than something to keep an eye on.

As for precipitation amounts, the latest GEFS is still bullish bringing over an inch of rainfall to many locations, with a 50-60 percent chance in far southeast SD, northwest IA and northeast NE. The latest AI model information leaning towards the lower side on rainfall amounts which worked well with the rain event this past Monday when many models (lower and hi res) and ensembles were indicating a widespread 1-2.5" of rain and we saw something closer to 0.50 to 1.25 inch rainfall amounts.

Aviation

Issued at 650 PM CDT Thu Oct 29 2026

MVFR ceilings and visibility will prevail for the majority of the period. Winds will be east to southeasterly and light around 10 kts. Winds will likely be too strong for widespread fog formation, but patchy fog is possible along river valleys and east of I-29 where they will be lightest. Confidence in fog impacting TAF sites was too low to include at this time. Any fog should burn off by mid-morning.

Stratus will flow in from south to north early Friday morning ahead of an approaching wave from the southwest. Ceilings will begin to lower as periodic light showers form along and south of Highway 20 around sunrise. Friday afternoon ceilings will become MVFR to IFR as showers become more numerous and move north, continuing through the end of the period. Afternoon winds will be southeast with 15-20 kt gusts.

Watches, warnings and advisories

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