textproduct: Sioux Falls

KEY MESSAGES

- After light showers exit this afternoon, more isolated showers may re-develop (10-20% chance) over southwest Minnesota by the late afternoon/early evening. Isolated wind gusts around 45 mph possible with this activity.

- More widespread rain risks return late Saturday into Sunday, though high uncertainty remains on the track of this system.

- Greatest severe weather risks remain focused south of the Missouri River and Highway 20 corridor Saturday.

- Forecast rainfall totals vary significantly through Sunday, though greatest potential for excessive rainfall remains just south of the forecast area. Ensemble probabilities for over an inch are 30-50% near the Missouri River.

UPDATE

Issued at 314 AM CDT Fri Jun 19 2026

Next wave is moving across the Dakota early this morning. Clouds increase, with isolated sprinkles through daybreak. Dry air should preclude precipitation for most of the area into mid morning. With light winds, some guidance hints at patchy fog east of I-29; however, confidence is low (less than 20%) in development with increasing clouds. Temperatures this morning have fallen into the 50s - on the cooler side for mid/late June.

Lowered highs for today from the NBM by a 2-4 degrees with the expected cloud cover and scattered periodic showers, especially with 925 mb temperatures near 20 deg C. This puts highs into the lower to upper 70s. If rain lingers into more of the day, would not be surprised to see more of the area in the lower 70s. Showers may struggle especially initially in the day due to drier low levels, but should increase in coverage through the late morning/early afternoon. Guidance maintained the later and more easterly shift in diurnally driven convection in MN later today, but still can't rule out an isolated stronger wind gusts around 45 mph (< 20% in occurrence) along/east of MN State Hwy 60. A couple rumbles of thunder are possible; severe weather is not expected.

Showers diminish tonight, with another cooler June night ahead.

DISCUSSION

Issued at 1247 PM CDT Thu Jun 18 2026

Still indications of some weak instability this afternoon, mainly over parts of southwest MN. This could generate a few showers, of which some gusty winds to 40 to 50 mph will be possible. This activity will be driven mainly by the heat of the day so should dissipate by about 9-10 pm.

A weak wave moves through Friday morning into the afternoon. The combination of a modest increase in moisture in the mid levels with weak instability above this moist layer, 700-500mb lapse rates about 7 degrees C, should allow for some ACCAS and showery activity during this time. If the clouds and mid level moisture can exit by mid afternoon, isolated diurnally driven showers may also pop up late afternoon into the evening. Impacts from this will be minor, but once again some gusty winds will be possible if some diurnally driven showers can develop with fairly unidirectional winds with height and fairly strong winds aloft.

Surface high pressure settles in Friday night into Saturday morning, which could result in a little patchy fog.The better chances look to be near the Big Sioux River Valley, but confidence is too low to include in the forecast.

Saturday should be a fairly pleasant day with increasing clouds and a fairly light easterly wind. Continued low humidity and highs mostly in the 70s.

Upper level low pressure rocks northward later Saturday night into Sunday morning. This lift will continue to fight the lower level dry air, but especially south of I-90 rain and very isolated thunderstorms will increase. With more confidence in this dry layer, rainfall amounts have trended downward.

Sunday into Monday poses more problems as the models disagree on handling the low pressure exiting. Rain chances should linger Sunday into Monday but confidence on where and especially amounts is very low.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 636 AM CDT Fri Jun 19 2026

VFR conditions expected through most of the period, outside of heavier showers. Scattered showers and isolated thunderstorms are expected through the afternoon hours. After showers move out of southwestern MN late this afternoon/early this evening, additional showers may develop. This later shower activity could produce some wind gusts to around 40 knots.

Winds through Saturday morning will vary from southwest to northwest, with gusts around 20 to 25 knots today (strongest north of I-90). Winds tonight become light and variable, with very patchy fog possible

FSD WATCHES/WARNINGS/ADVISORIES

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