textproduct: Sioux Falls

KEY MESSAGES

- Dry and seasonably warm through this afternoon. Breezy south winds gust 30 to 40 mph, highest west of I-29.

- Shower and storm chances return later today through tonight. Isolated strong to severe storms are possible in portions of southeastern South Dakota and far western Minnesota later this evening. Wind gusts to 65 mph and quarter sized hail are the main threats.

- Cooler temperatures mid week with scattered showers and storms. Seasonal temperatures return late week, with low and uncertain rain chances into the weekend.

UPDATE

Issued at 334 AM CDT Mon Aug 3 2026

Pleasant and warm start to the morning, albeit a bit breezy with southerly wind gusts 25-30 mph. Winds are light across northwestern IA, so may see some brief and extremely patchy fog toward/east of the US Hwy 59 corridor. With compressing SPG ahead of the surface cold front, expect wind gusts today around 30-40 mph, with a few isolated higher gusts west of I-29. Seasonal conditions prevail.

No significant changes to the short term forecast. Minor adjustments to the Day 1 SPC outlook, shifting the Marginal (level 1 of 5) risk back to the west slightly. Biggest challenge in the short term remains the timing and development of convection with the surface front and the trailing wave as well as how much we destabilize. Some of the latest guidance indicates that there may still be a modest cap in place (especially looking at soundings), and that instability and shear may be offset slightly through the evening hours. There may be a narrow window this evening from 7 PM through midnight where strong to severe storms (likely elevated storms) may produce wind gusts to 65 mph and quarter sized hail in the western parts of our forecast area.

Showers and storms may become more widespread through the overnight hours as the mid/upper level wave and front move in, providing the synoptic support. However, decreasing instability and still slightly offset shear should limit severity as storms continue to press east overnight into early Tuesday.

DISCUSSION

Issued at 151 PM CDT Sun Aug 2 2026

Clear skies persist across the area this afternoon as high temperatures have warmed to the 80s. Winds remain more on the breezy side, mainly for locations along and west of the James River where gusts up to 20-30 mph are being observed. Winds will weaken some through the evening hours but remain elevated overnight as an upper level wave begins to eject into the Northern Plains, strengthening the low level jet (LLJ). The LLJ will also keep low temperatures on the warm side with lows only falling to the 60s to low 70s overnight. Patchy valley fog is possible again tonight though northwest Iowa will have the best potential for fog as winds will be weakest there.

Monday will be a warmer day as high temperatures warm to the 80s and 90s. With will remain breezy with gusts up to 35 mph expected during the afternoon time frame. A cold front will be pushing into the area from the west by the late afternoon and early evening timeframe. This front may have the potential to develop showers and thunderstorms. However, steep mid level lapse rates will yield a stout capping inversion. There also looks to be mid to high level clouds situated above the front throughout the day on Monday that could result in slightly cooler temperatures. That said, both the HREF and REFS have decreased their probabilities for a strong cap to remain in place. They now show a 40-70% chance for convective inhibition (CIN) to remain at -50 J/kg or less. This suggests that the cap could be weak enough for one or two storms to develop along the cold front as it pushes into the Missouri River Valley. This potential is still uncertain as the latest 12z hi-res guidance shows some variance in storms developing along the front. This may be a scenario where storms develop in the evening along the elevated portion of the cold front where CIN will be less. Should storms develop, they continue to look to be just ahead of the stronger vertical shear. Still not out of the question for these isolated storms to be strong to severe. Effective shear values look to be on the order of about 40 knots while min to max theta-e difference values will be down to about -15K. Thus, large hail up to the size of half dollars and damaging winds to 60 mph will be possible if the isolated storms do develop. Chances for strong to severe storms will be waning into the overnight hours but rain showers look to persist through the night along the elevated front.

The surface front will push through the forecast area during the overnight hours. However, the elevated front will remain over mainly northwest Iowa for the day. This is where the bulk of the rain is expected to fall. The rain and cloud cover will keep high temperatures on the cool side with highs only reaching up to the 70s. The rain will persist through the entirety of Tuesday and through Wednesday morning before pushing southeast of the area. The ensembles continue to show moderate to high probabilities between a 50-80% chance for rainfall amounts to exceed a tenth of an inch. Their probabilities decrease to 0-40% and are concentrated along and south of highway-20. Thus, light rainfall amounts of a tenth of an inch to possibly exceeding a quarter of an inch is most likely at this time.

With lingering cloud cover around, Wednesday will be another cool day with highs only warming to the 70s. Broad troughing will will reside over the Northern Plains for the back half of the week and next weekend. Temperatures look to warm back to near seasonable in the 80s to potentially 90s each day. There could potentially be more chances for rain but these chances are uncertain for now.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 625 AM CDT Mon Aug 3 2026

VFR conditions prevail through much of the period. Main aviation concerns will be breezy conditions today, showers/storms late this evening into the overnight hours which could lead to reduced visibility/ceilings, and some lower level smoke (restrictions uncertain).

Southerly winds increase through this morning with gusts this afternoon 25-35 knots, strongest and isolated higher west of I-29. Some directional LLWS is expected through 14z west of the James River. Winds remain strong into tonight, but shift northwesterly behind a cold front.

Showers/storms develop late this evening and into tonight near the aforementioned cold front. Some uncertainty in exact timing and coverage, so maintained PROB30 groups for now. A stronger storm could produce wind gusts around 55 knots or higher and quarter size hail after 04.00z through around 04.05z. Expect storms to produce MVFR and possibly lower conditions in heavy rainfall. Showers/storms continue moving east through the end of the period.

Finally, models bring some higher concentrations of smoke to the surface later in the period. Given uncertainty in impacts, have left out of TAFs for now.

FSD WATCHES/WARNINGS/ADVISORIES

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