textproduct: Sioux Falls

KEY MESSAGES

- Showers and very isolated thunderstorms are likely tonight into Saturday morning, mainly near and east of Highway 81. Drizzle and spotty showers will be possible west of Highway 81. No severe weather expected.

- A more widespread rain returns later Sunday night into Monday night. The latest guidance suggests about a 60-90 percent chance for more than an inch of rain. Flooding is unlikely, but not zero. Additional rainfall is likely on Tuesday.

- A low confidence threat for low topped supercells Monday afternoon and evening in far southeast SD, northeast NE and northwest IA.

DISCUSSION

Issued at 148 PM CDT Fri Oct 30 2026

Showers remain likely tonight into Saturday morning as low level moisture deepens, roughly the lowest 5 km, and marginally dry, cooler air above this layer allows for weak instability, generally 200-500 J/kg CAPE. This should generate mainly showers, but a few lightning strikes will be possible. Rainfall amounts will mostly be light, but some pockets of a tenth of two will be possible.

Saturday night into Sunday should be mostly dry, but moist neutral soundings and lingering moisture/cloud cover may allow for some patchy drizzle and showers. Overall low impact, but likely not an entirely dry period.

A fairly well agreed upon trough of low pressure will move onto the Plains Sunday night, deepening on Monday as a strong southern stream jet strengthens. This should provide that area with widespread rainfall and if everything comes together timingwise, the threat for an isolated tornado over southeast parts of the area.

All models continue to indicate a widespread 1-2" of rainfall from Sunday night into Tuesday morning. Very little disagreement for the most part on timing and location of the rainfall. Given a fairly wet pattern the past 6 weeks or so river flooding could start to become a problem. But for now, the latest hydrologic modeling suggests at least 2.5-4" of rain would be needed to push rivers to action stage and minor flooding, so for now chances of river flooding are pretty low (<20 percent). Also suggestions that 1.5" of rain in an hour could produce some localized flash flooding, but for now the rainfall rates should not be quite that high. All in all, it looks like a band of warm advection rainfall will lift northward Sunday night into Monday. Later Monday afternoon into Monday night a dry slot could move in and if convection does not develop, a dry period or period of drizzle will be possible. Then later Monday night into Tuesday wrap around rainfall will move through.

While this is a very low threat probability, we will need to keep an eye on the development of surface low pressure Monday afternoon as the upper level wave moves through. Starting to see indications this surface low pressure could end up near southeast SD/northwest IA which could bring about a threat for some low topped supercells/isolated tornadoes. The 6z ensemble data has the EC placing this SFC low in southeast SD late Monday afternoon while the GEFS and Canadian Ensemble are in eastern NE. Obviously a big difference so trends will need to be monitored. The 12z GFS is now placing the surface low in southeast SD late Monday afternoon as well.

Tuesday will likely see some wrap around rainfall continue, but should diminish throughout the day. Wednesday through Friday should be mostly dry and cooler with highs from the upper 40s to mid 50s.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1231 PM CDT Fri Oct 30 2026

MVFR ceilings will continue to overspread the area from south to north through the afternoon. These ceilings will further fall into the IFR category after sunset through midnight for most locations. Scattered showers and very isolated thunderstorms will develop and move northward through the night into Saturday morning. This activity will diminish from mid morning into Saturday afternoon. Ceilings will then improve from south to north through the day Saturday.

FSD WATCHES/WARNINGS/ADVISORIES

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