textproduct: Sioux Falls

KEY MESSAGES

- Widespread showers with isolated thunderstorms will continue today. With pockets of moderate to briefly heavy rain expected, accumulations between 0.50" to 1.00" inches is expected for most areas with slightly higher accumulations possible east of I-29.

- While severe weather is not expected, developing thunderstorms could produce strong wind gusts up to 45 mph and pockets of heavy rainfall mainly across northwestern IA. A very brief funnel cloud risk will also be possible with developing storms.

- Below normal temperatures will continue through Saturday before warmer conditions return from Sunday onwards.

UPDATE

Issued at 354 AM CDT Fri May 22 2026

A dreary day is ahead! Taking a look across the area, we're continuing to see light to moderate showers progress through portions of northwestern IA this morning mainly in response to increasing lift ahead of our main wave. As we head towards daybreak, should see shower coverage gradually become more widespread as the 850mb LLJ strengthen within the warm air advection regime. Increasing precipitation rates could lead to rapid accumulations at times. However, most areas are still on track for between 0.50" to 1.00" inches with slight higher accumulations (1.25"-1.75") possible along and east of I-29. Shifting gears here, a low CAPE/high shear environment could lead to some convection developing across portions of northwestern IA and the lower Missouri River Valley this afternoon.

While severe weather is not expected, developing thunderstorms could produce wind gusts up to 45 mph and pockets of heavier rainfall. Otherwise, with a vertically stacked low overhead and veering wind profiles according to soundings; the enhanced stretching potential could lead to few cold air funnels between the James River Valley and I-29 corridors this afternoon. While the chances are low, the lower LCLs and environmental factors should be conducive for some brief development mainly between 2pm to 8pm. Lastly, with most of this activity lifting out of our area by this evening; could see some patchy fog develop mainly in our river valleys.

DISCUSSION

Issued at 230 PM CDT Thu May 21 2026

Scattered clouds will increase late this afternoon ahead of an approaching upper trough and embedded shortwave. Good mixing will allow southeast winds to tap into a modest LLJ. Resultant afternoon winds will be breezy gusting 20-25 mph. Winds decrease slightly after sunset but remain on the breezy side overnight gusting to 20 mph. Highs today will be cooler, in the 60s and 70s. Overnight lows look to fall to 40s. Chances for showers increase late this afternoon and evening as the previously mentioned short wave enters south central South Dakota. Isolated to scattered showers will gradually flow in from the south, expanding in coverage across most of the region by sunrise. Severe weather is not expected.

Beginning very early Friday morning plentiful moisture will advect north thanks to a weak theta e ridge and pool ahead of an approaching cold front. Despite the push of warm and moist air, instability remains low, generally less than 300 J/kg. However, this is enough for a few rumbles of thunder. By Friday mid- morning a region of enhanced vorticity enters central South Dakota and WAA and the LLJ ramp up. The increased forcing will result in scattered showers becoming more numerous and broader in areal coverage. Lightning risks increase as well. Periods of heavier rainfall may occur, up to around 0.25 inch per hour. As the cold front continues to progress east Friday afternoon a region of strong vorticity advection associated with the surface low will work to focus storms into a more organized convective line. A few stronger storms may produce frequent lightning and wind gusts up to 40 mph, but severe weather is not expected. Brief heavy down pours are possible under any of the stronger storms that form. The more organized line looks to set up just to the west of I-29 and progress eastward between 2 and 10 pm CDT. Storms should push east of the region shortly after midnight. Additional light showers are possible as moisture wraps around the low, mainly along and north of Highway 14 Saturday morning. Very little additional accumulation is expected. HREF LPMM indicates rainfall totals of a quarter of an inch up to 1 inch for the majority of the region. Portions of northeast Nebraska and northwest Iowa could possibly see 1.25 inches plus. Guidance has in general been trending totals up the past few runs, if this trend continues some areas may even see up to 2 inches.

Winds continue to increase through Friday afternoon as the SPG tightens further. Peak winds are expected in the late morning to early afternoon. Widespread gusts of 25-30 mph are expected with occasional gusts to 35 mph possible. Winds will decrease after sunset, becoming light overnight. Highs for Friday will be cool in the 50s to low 60s. Lows will be in the 40s.

Saturday, mostly cloudy skies will become scattered through the day. Winds will be light and highs will be slightly warmer in the upper 60s to mid-70s. A few isolated light showers are possible in the very early hours Sunday morning as an upper wave axis crosses through the region. Very little accumulation is expected. Showers end shortly after sunrise. The rest of Sunday will be beautiful day with mostly clear skies and highs in the upper 70s to low 80s. Afternoon southerly winds will be on the breezy side, gusting around 20 to 25 mph.

Late Sunday night into Monday morning another round of showers and thunderstorms are possible as an upper wave and WAA make their way through the region. While convective parameters are generally good, confidence in strong storms is low due to a wide variance in guidance. Showers should clear out Monday late morning. Highs will be in the 80s and 90s with breezy afternoon southerly winds. From Tuesday onward an upper ridge will build over the region. Dry conditions are expected to prevail with highs in the 80s. By Thursday night a more progressive upper wave may move through the region. But details are uncertain at this time.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1247 PM CDT Fri May 22 2026

Showers and thunderstorms have begun to wane this afternoon. Areas to the east of I-29 will continue to see more organized showers and possibly a thunderstorm or two for the next couple hours. Precipitation should be fully clear of the area by early evening tonight. A mix of MVFR down to LIFR ceilings and visibilities will improve in concert with the showers as they move to the northeast. VFR conditions should be widespread once again around midnight.

Afternoon winds are southeasterly ahead of the surface front, becoming westerly behind. Breezy gusts of 15-25 kts will taper off after sunset becoming light. As they do so patchy dense fog may develop early Saturday morning. Any fog should burn off by mid- morning.

FSD WATCHES/WARNINGS/ADVISORIES

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