textproduct: Sioux Falls

KEY MESSAGES

- Pockets of heavy rain will be possible mainly near and south of highway 20 in northwest IA late this morning into this afternoon. Confidence on the extent of heavy rain is low.

- Low stratus and fog remain possible tonight into Saturday night. Lower confidence for stratus and fog Sunday into Sunday night with a small push of drier air.

- Monday night into Tuesday night is the next better chance for showers and thunderstorms. Isolated severe storms and pockets of heavy rain will be possible.

DISCUSSION

Issued at 1236 PM CDT Fri Aug 14 2026

Low pressure continues to track east northeast into western IA through this afternoon. Scattered showers and isolated thunderstorms will be possible with this feature. The main effects should be this afternoon and confined to areas near and south of highway 20 in northwest IA. With PWAT values around 1.75" to 2", locally heavy rain will be possible, especially near this low pressure along and south of highway 20. Some question marks surround the air mass in Woodbury and Ida counties, locations that have received the most rainfall the past two days, as the morning stratiform rainfall seems to be providing some stability to the area and suppressing stronger convective activity. The latest Hi-res models continue to trend away from heavier rain near highway 20, with mainly spotty activity expected. A few downpours could lead to very localized amounts around an inch or so, but flash flooding is unlikely. Farther northwest, spotty showers will be possible with weak, diurnally driven instability. The overall effects of these diurnally driven showers will be low.

Saturday will likely start with stratus and fog in many locations. A weak wave will move through the area and likely lead to spotty showers and thunderstorms. Some hints that the better instability (about 1000 J/kg) will be north of I-90, but overall weak shear and 13 kft freezing levels suggest that pockets of heavy rain will be the main threat.

By Saturday night this wave will move southeast of the area, leaving mainly dry conditions in place for much of Saturday night into Sunday morning. Model soundings hint at the potential for some morning fog, but the depth of the low level moist layer looks much shallower, so a better chance to burn off in the morning. Drier northerly flow should lead to a pleasant Sunday with highs of 75 to 80 and dew points likely in the lower to mid 60s for most locations.

Sunday night into Monday should see mostly dry and warm conditions continue. Monday night into Tuesday night will be the next better chance for showers and storms as a trough digs in to the north and northeast. For now, the threat for severe storms and heavy rain looks low, but this will be a time frame to watch for changes.

Cooler and more stable air should settle in behind this system, with highs mostly in the 70s Thursday and Friday and only isolated chances for showers and storms.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1236 PM CDT Fri Aug 14 2026

Widespread MVFR and IFR conditions are expected through most of the TAF period. Scattered showers, drizzle and isolated thunderstorms, mainly northeast NE, southeast SD and northwest IA are expected through about 2z. Spotty heavy rain is possible in northwest IA this afternoon.

FSD WATCHES/WARNINGS/ADVISORIES

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