textproduct: Sioux Falls

KEY MESSAGES

- 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.

- Scattered showers and a few storms are likely to develop Saturday afternoon especially near and east of I-29. Heavy rainfall will be the main concern, but a wind gust to 45 mph can't be ruled out in the strongest storm.

- 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.

UPDATE

Issued at 953 PM CDT Fri Aug 14 2026

Ample moisture across the area will lead to the continued development of low stratus and even some fog after midnight. Locally dense fog will be possible especially where skies can clear up a bit. Make sure to use extra caution on the roads tomorrow morning as visibilities may be fine in your location but not in the place you are heading to! Any fog should lift by 9 am. Due to cloud cover, temperatures won't fall all that much overnight, with lows by sunrise mainly in the middle to upper 60s.

Low clouds that linger into the morning hours will begin to lift and erode by the late morning and into the early afternoon. The sunshine that breaks through these clouds should provide efficient destabilization in the afternoon as a weak wave and cool front moves across the area. This will lead to shower and storm development especially near and east of I-29 where the front moves through closest to peak daytime heating. There will be little CIN and around 1,000 to 2,000 J/kg of SBCAPE, with CAPE profiles once again favoring heavy rain as the main threat. Some of the CAMs are showing some pretty high rainfall rates (potentially up to 2" an hour); but this activity should be progressive enough to preclude flash flooding concerns. But be prepared to take it slow on the roads if driving through this heavy rain!

Shear will be a bit better Saturday than what we had today, but still fairly weak overall and so this should limit severe potential. But with better instability and a bit of dry mid level air, can't rule out a wind gust to 45 mph especially south of I-90 where the better instability lies. If morning clouds take a bit longer to clear, then the chance for heavier thunderstorms will be lower. Guidance also hints that additional showers and isolated thunderstorms may also develop along an 850 mb boundary that will trail the cool front, but this would only really be a very isolated lightning concern for those with outdoor activities planned.

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 /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 658 PM CDT Fri Aug 14 2026

MVFR to IFR and locally LIFR stratus will impact the area through tonight and into tomorrow morning. Patchy fog is also possible late tonight and into early tomorrow morning. This stratus should gradually lift and erode through the early afternoon hours on Saturday generally from west to east across the area.

Thunder potential will remain very low through the early morning hours tomorrow, though a better chance of some pop-up thunderstorms will be from the mid-morninng onwards. Confidence in thunder potential remains low for tomorrow afternoon, so left out any mention in the TAFs at this time.

Winds will be light and variable through the early morning hours, with a slight uptick in west-northwesterly winds during the afternoon hours Saturday. Highest gusts will only be around 15 kts or slightly higher Saturday afternoon.

FSD WATCHES/WARNINGS/ADVISORIES

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