textproduct: Sioux Falls

KEY MESSAGES

- Isolated showers and storms diminish very early this morning.

- A band of showers and isolated thunderstorms are likely Tuesday evening and night, with the better chances northeast of a Huron to Spencer IA line. Severe weather is not expected.

- Wednesday will be windy as a spring-like system moves through. Gusts of 45 to 50 mph are likely. Scattered afternoon and evening showers may also bring additional gusty wind threats.

UPDATE

Issued at 846 PM CDT Mon Jun 15 2026

Scattered showers and very isolated thunderstorms move southeast through this evening, diminishing through the late evening hours. Showers have been producing gusts at times earlier in the evening to around 55 mph, but highest recent gusts have been closer to 50 mph over the last hour. Rainfall amounts have been light given the very high cloud bases - generally a couple hundredths of an inch or less (outside thunderstorms). Activity should move out of the area by midnight or a bit after.

Temperatures behind these showers are falling into the 60s, and fall into the 50s later tonight. With some clouds around, it will be another pleasant June night. Winds become a bit lighter overnight, which may lead to some fog development in the James and MO River Valleys, as well as between the James River Valley and the Buffalo Ridge. Confidence is low given the spread in the models, but patchy fog may reduce visibility into the early part of the Tuesday morning commute.

No significant changes to Tuesday onward; see below for details.

DISCUSSION

Issued at 1257 PM CDT Mon Jun 15 2026

Model soundings and the latest hi-res models continue to indicate the potential for strong wind gusts with any shower and thunderstorm activity that develops this afternoon and evening. These wind gusts will be tied to surface based instability of about 200-500 J/kg. Given the diurnal nature of this activity, the best chance for the strong wind gusts will be roughly 4 pm to 9 pm. Only very isolated activity will linger through about 10 pm to midnight. Otherwise a little patchy fog will be possible around the Kingsbury and Brookings county areas late tonight and early Tuesday morning.

An unseasonably strong jet max will dive southeast Tuesday into Wednesday. As this jet max moves into the area Tuesday, warm advection will increase with the chances for showers and isolated thunderstorms arriving possibly during the afternoon, but the better chances will be at night. While forcing is fairly strong, instability is lacking due to a fairly deep dry layer in the lower levels. However, with the EML running around 7.5 C and some decent forcing, showers and isolated thunderstorms will be possible with this shot of lift. The better chances appear to be near and northeast of a Huron to Spencer IA line with the best chances in southwest MN.

This almost spring or fall like system will bring strong surface winds to the area Wednesday. Gusts of 45 to 50 mph will be likely during the day as mixing brings down some very strong winds aloft. The latest models show a 130 knot jet around 300 mb, with unidirectional flow from the west northwest throughout the atmosphere. While we will have a small convective threat on Wednesday afternoon and evening, model soundings indicate weaker instability than today, but still some 100-300 J/kg surface based CAPE mainly north of I-90. With the strong, unidirectional winds, wind gusts around 50 mph with these showers will be possible.

Broad troughiness moves through Thursday and should bring quieter weather and seasonably cool conditions.

Weak upper level ridging builds on Friday and will keep quiet weather in place with temperatures back into the upper 70s to mid 80s.

Saturday will see a system pass by, possibly a bit to the south. However this will be the next better chance for showers and storms with isolated severe storms possible. Something worth keeping an eye on.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1220 AM CDT Tue Jun 16 2026

Very isolated showers/storms near US Hwy 20 come to an end by 07z. Seeing some occasional wind gusts around 20 knots, but these should remain infrequent for the next couple hours, with winds becoming light. Light winds may lead to some very patchy fog development in river valleys and between the James River and the Buffalo Ridge, but confidence in occurrence remains below 20%.

Winds shift westerly through the morning Tuesday, becoming southerly toward the end of the period with gusts around 20 to 25 knots. LLWS is possible toward the end of the period along/south of I-90; however, directional shear is marginal and speed shear looks to be below 30 knots with any gusts, so have omitted for now.

Scattered showers and thunderstorms return to the area Tuesday afternoon and continue through Tuesday night. Confidence is too low to mention any late afternoon/early evening convection at KHON or KFSD. Best chances move into northern US Hwy 14 corridor after 17.00z, so have included mention in a PROB30 group at KHON for now.

FSD WATCHES/WARNINGS/ADVISORIES

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