textproduct: Sioux Falls

KEY MESSAGES

- Patchy valley fog may lead to visibility below one mile at times through 9 AM or so. Otherwise, dry and warmer today; breezy west of I-29.

- Storms may develop Friday late afternoon and evening. If storms develop, they may quickly become strong to severe. Confidence in development and coverage remains low due to strong capping potential.

- Additional moderate to high chances (50-80 percent) for showers and thunderstorms return late Saturday night into early next week. Heavy rain is possible Sunday, with isolated strong storms possible Monday.

- Cooler conditions arrive this weekend into much of next week. Occasional shower and storm chances linger mid next week.

UPDATE

Issued at 313 AM CDT Thu Sep 10 2026

No significant changes to the forecast this morning. Keeping an eye on potential for valley fog, but thus far have not seen much development. Any fog that does develop this morning should be largely confined to river valleys and quickly mix out an hour or two after daybreak, but visibility may fall below one mile at times. Temperatures are near seasonal averages, in the 50s this morning.

Still anticipate a warmer day as surface high pressure slides east and southerly LL flow returns. Highs in the 80s for most, with breezy conditions (gusts 30-35 mph) west of I-29. Winds increase tonight as the surface pressure gradient compresses ahead of a cold front Friday. Lows a bit warmer with WAA and southerly flow - in the 60s. Have kept the forecast dry for tonight into Friday morning as any moist layer aloft is very narrow and any shower/sprinkle that develops in the WAA/weak wave will struggle.

No major changes to the severe threat Friday afternoon/evening, as guidance continues to show the better forcing and dynamics to our north and east, with a strong cap overhead. CAMs largely keep convection out of our area, but if we're able to break the cap, storms may quickly become strong to severe. More details below in the DISCUSSION section.

Scattered showers and storms continue into early next week. Locally heavy rain looks to the main threat Sunday, with isolated stronger storms possibly returning to the area Monday.

DISCUSSION

Issued at 1251 PM CDT Wed Sep 9 2026

High pressure settle south tonight and should lead to some crisp morning temperatures on Thursday. Look for morning lows from the mid 40s in the lower spots to the lower 50s.

Return flow sets up through the day Thursday with southerly winds likely gusting to 25 mph west of I-29. Highs will generally climb into the 80s, with some 70s across parts of northwest IA and southwest MN.

The leading edge of a mid level wave will sneak into central SD late Thursday night into Friday morning, resulting in increased low to mid level warm advection. While most of the area is capped due to dry air, a small wedge of increased moisture around 8000 feet may bring weak, 200-400 J/kg, elevated instability based around 8000 feet. This could result in some ACCAS on Friday morning, with impacts on the minor side.

This wave will deepen a bit and track just north of the area on Friday afternoon and evening, leading to a wedge of increased temperatures in the low levels. This will lead to widespread highs in the mid 80s to lower 90s. The question then comes to what are the convective chances as this wedge of warm air settle south and cooler air filters in behind on Friday night. The environment ahead of this front will be fairly unstable, 2000-3000 J/kg, with about 40 knots of deep layer shear. The lower levels show a nice south to southwest inflow, suggesting that new updrafts may be on the southwest flank of any development. Given the instability and shear as well as the potential for discrete cellular development, all modes of severe weather will be possible, including golf ball sized hail, wind gusts to 70 mph and isolated tornadoes. The main negative will be the potential for a fairly strong capping inversion. This suggests that there may be a very small window shortly before sunset to get any strong updrafts going that could produce higher end severe weather.

As this system lifts east northeast Friday night, cooler and drier air will settle southward and bring a pleasant Saturday with highs in the 70s and dew points in the 45 to 55 degree range.

A stronger system works onto the Northern Plains Sunday into early Monday and should bring a more widespread area of showers and thunderstorms to the region. The latest ensemble output from the GEFS, EC and Canadian all suggest about a 30-60 percent chance for a half an inch or more of rainfall for much of the area with a slight lean towards the better chances near and north of I-90.

West to southwest flow aloft continues through mid week keeping the chances for showers and thunderstorms in the area during this time. With slightly cooler air in place behind the Sunday system and the potential for clouds and precipitation, temperatures will be a bit cooler with highs in the 70s and lows in the upper 40s to mid 50s.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 1220 AM CDT Thu Sep 10 2026

VFR conditions will prevail for the rest of the period. Besides some high level cirrus overnight, patchy VFR to MVFR fog will be possible as winds become more light and variable. Otherwise, should see VFR conditions return after daybreak. Light and variable surface winds overnight will become more southeasterly by Thursday afternoon and breezy with gusts between 20-30 mph expected. Lastly, a strengthening LLJ will lead to a couple hours of LLWS mainly at KFSD from Thursday night into Friday.

FSD WATCHES/WARNINGS/ADVISORIES

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