textproduct: Sioux Falls

KEY MESSAGES

- Patchy fog remains possible (30-60% chance) through about 8 am for northwestern Iowa and adjacent areas of far southwestern Minnesota and far southeastern South Dakota. Widespread fog is not expected.

- Greatest severe weather threat remains focused south of the Missouri River through the weekend.

- Models remain consistent in keeping the highest rainfall south of the Missouri River and into south central South Dakota through Sunday. Chances for exceeding an inch of rain through Sunday night in this area is 35-60%.

- Below normal temperatures and periodic rain chances continue into the start of next week. Severe weather chances remain low.

UPDATE

Issued at 304 AM CDT Sat Jun 20 2026

Forecast remains largely on track this morning, with some minor adjustments through Sunday to pops.

Satellite and observations show some patchy fog developing across parts of northwestern IA. Guidance limits the extent to mostly river valleys and other low lying areas. Some locations could see visibility below a mile for a brief time; however, one wrench in extent will be the mid/upper clouds moving in from the west. We're starting off cool with temperatures in the upper 40s and 50s.

Most of the day remains dry, with rain chances increasing late this morning for the MO River Valley, spreading north through the day and tonight. Highs in the 70s.

For the weekend, severe weather risk remains very low with weak (< 750 J/kg) of 0-3km MUCAPE - highest Sunday in Gregory county. Although we'll have ample shear and some increase in mid level lapse rates, better dynamics and forcing are focused south of our area.

Ensemble probability of 0.5" or more in any 6 hour period through the weekend remain around 45% or less, focused along and south of the MO River and into portions of south central SD tonight into Sunday. For most of the MO River Valley where guidance shows the heaviest rainfall, 6 hourly flash flood guidance is near or above 3 inches, with even some locations near 4" in a 6 hourly period. With ensembles showing a low (30% or less) chance for more than 1.5" of rain through Sunday night, flash flooding continues to look unlikely.

DISCUSSION

Issued at 134 PM CDT Fri Jun 19 2026

Showers will exit the area late this afternoon as the weak wave pushes east. Rainfall amounts continue to remain on the light side. A very small chance for an isolated shower/thunderstorm in southwest MN this evening. If something can develop a wind gust to 40 mph will be possible. Otherwise, behind the weak wave that brought these showers, surface high pressure will nudge into the area with temperatures expected to fall into the upper 40s to lower 50s on Saturday morning.

Saturday looks dry and mild with light winds. After the cool morning starts, highs should mostly be in the 70s.

Saturday night into Sunday will see upper level low pressure settle into the area with broad low to mid level warm air advection locking into place. Overall the instability is on the weak side so severe weather chances remain very low. Even the heavy rain threat is pretty muted, with mainly the Missouri River area seeing a chance for an inch or more of rainfall into Monday morning. Given the very dry conditions will need to see much more then 1-2" of rain over a 24 to 36 hour period to have any concern for flooding or flash flooding. And given the expected weaker instability, brief rainfall rates of 2-4" per hour also seem very unlikely.

Next week will see continued northwest flow aloft which will limit any instability that can build into the area. There will be a few waves that move through the area in this northwest flow, but the threat for heavy rain and severe weather will be low. This northwest flow will also keep cooler conditions in place with below normal temperatures expected each day.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 1230 AM CDT Sat Jun 20 2026

Patchy fog remains possible (35-55% chance) through about 20.13Z mainly for northwest Iowa and adjacent portions of southwest Minnesota and southeast South Dakota. Widespread fog is not expected and dense fog is unlikely (<15% chance). After fog lifts, expect VFR conditions through the rest of the period, except for areas near and south of the Missouri River Valley. This is where a developing storm system will send MVFR CIGS and showers/isolated thunderstorms gradually through the late afternoon and into the early evening hours.

Winds will be fairly light through the period for most of the area. However, higher winds are expected over south-central South Dakota, where sustained southeasterly winds will generally be around 10-15 kts this afternoon and evening. Gusts in these areas will top out around 25 kts.

FSD WATCHES/WARNINGS/ADVISORIES

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