textproduct: Sioux Falls

KEY MESSAGES

- Steady rain/drizzle exits off to the northeast through the afternoon. Scattered showers will redevelop this afternoon mainly east of the James River, but not everyone will get rain from this activity.

- Additional showers and storms look to redevelop in northwest Iowa this evening into the early overnight. Severe weather is not expected, but brief heavy downpours can be expected if a thunderstorm develops.

- After a brief break late Sunday into Monday, rain chances return Monday night into Tuesday. Pockets of heavier rainfall will again be the primary concern.

DISCUSSION

Issued at 257 PM CDT Sat Sep 26 2026

The area of steady moderate rain that impacted the area this morning is exiting off to our northeast; however, patchy drizzle continues and will continue on and off through the afternoon where clouds ceilings are lowest, which is generally from far eastern South Dakota into southwest Minnesota. Farther west, we've seen some breaks in the lowest clouds, allowing for some destabilization to occur. Up to 500-1,000 J/kg of MLCAPE has developed per latest SPC Mesoanalysis along the Missouri River Valley, and as a secondary mid level wave moves across the area, a few weak thunderstorms have already developed over northern Nebraska and are lifting northward. Severe weather is not expected given weak shear across the area, but we will likely continue to see some additional showers and isolated thunderstorms develop through the afternoon and evening. The best chance of rain (30-60%) with this activity will be over western Iowa, far northeast Nebraska, and far southeast South Dakota, stretching to far southern Minnesota by the late night hours. Tall, skinny CAPE profiles and deep warm cloud layers suggest heavy rain will be the primary threat with any thunderstorm. This could lead to a few pockets of ponding in low- lying and poor drainage areas, but flash flooding is unlikely.

Heading into tonight, the areas that saw some clearing stratus (primarily near and west of the James River) will see some fog develop, meanwhile the stratus deck elsewhere is expected to lower through the night and become fog. Locally dense fog is likely given all the near surface moisture, though coverage and exact locations where the densest fog will reside precludes a need for a Dense Fog Advisory at this time, but trends will be monitored. This fog will gradually lift through the mid morning hours, but likely become low stratus heading into much of the day on Sunday. Still the potential for some of this stratus to mix out a bit and allow for brief breaks of sun mainly near and west of the James River, but this will likely be the exception, not the norm across the area. Some instability in the low cloud layer may allow for a few sprinkles to spits of drizzle, but it's not looking as persistent as it has been the past couple of days.

Heading into early next week, a trough over the West Coast will begin to dig into the Desert Southwest. Ahead of this, an upper wave will move into the area late Monday into the day on Tuesday and bring our next round of rain and storms to the area. Latest GEFS shows around a 30-40% chance of at least an inch of rain mainly focused over northwest Iowa and adjacent areas. This is a bit higher than other guidance, but appears to be the most reasonable at this time given ensemble PWATs show anomalies nearly of +1" in place as this system moves through. The aforementioned trough over the Desert Southwest will absorb the remnants of a Pacific Ocean tropical cyclone as it ejects to the north and east during the middle to end of the next work. This may help to keep a decent amount of moisture in place over primarily northwestern Iowa into the end of the upcoming work week, though at this point it looks like the heaviest rain associated with this will stay south of the area.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1249 PM CDT Sat Sep 26 2026

An area of steady light to moderate rain exits off to the northeast to start the period, though some drizzle will continue in its wake. Starting to see clouds scatter out in portions of South Dakota west of the James River early this afternoon, which will likely be confined to these areas. However, stratus where it does stick around with lift a little bit through the afternoon, with the return of MVFR cigs expected west of I-29, with perhaps some brief pockets of MVFR cigs along the I-29 corridor late this afternoon. Cigs will drop area-wide once again tonight, and fog looks to develop, some of which could be locally dense at times. Fog should lift by the mid-morning Sunday, though IFR stratus likely lingers after it to end the period.

In terms of rain chances this evening and overnight, a few showers and isolated thunderstorms look to develop mainly near and east of I- 29, with the better chances (20-40%) of a thunderstorm over northwest Iowa, northeast Nebraska, and far southern Minnesota. Southeasterly winds will gradually diminish through the afternoon and evening, with winds becoming light and variable to calm overnight. Light northeasterly winds will end the period during the late morning.

FSD WATCHES/WARNINGS/ADVISORIES

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