textproduct: Sioux Falls

KEY MESSAGES

- Warm conditions Saturday with highs in the upper 80s and low 90s. Southeast winds will be breezy, gusting 25-35 mph over central South dakota and decreasing as you move east.

- Low chances (<25%) for showers and thunderstorms along and south of Highway 20 Saturday evening and overnight. - A system wraps north Sunday into Monday and will bring scattered showers and thunderstorms to the area. Severe weather chances are currently low.

- Temperatures heat up this weekend into next week. There is an increasing chance (30-70%) of highs exceeding 95 degrees mainly near and west of the James River by Tuesday and especially Wednesday. Be prepared to enact any heat related safety measures.

UPDATE

Issued at 841 PM CDT Fri Jun 5 2026

Mostly clear skies along with light and variable winds will allow for good radiational cooling tonight. Patchy dense fog is possible as a result. The most likely areas to see fog are near and east of Highway 81, and along the James River Valley. As you make your way early Saturday morning, please ensure you are prepared for changing driving conditions. Fog should burn off by mid-morning.

For the rest of Saturday mostly clear skies will prevail as highs climb into the upper 80s and low 90s. For reference, average high temperatures for early June are in the mid to upper 70s. However, we will still be ten or more degrees off from breaking any high temperature records. Overnight lows will be warm in the mid to upper 60s.

A lee trough develops late Saturday afternoon over eastern Montana, Wyoming, and Colorado. As this pushes east the SPG will tighten and the LLJ will intensify. Southeast winds are well aligned from the surface through the 800-750 mb layer. Good mixing will tap into the LLJ and we can expect increasing wind gusts at the surface. The strongest winds will be for areas west of Highway 81, where 25-35 mph gusts are possible. East of there to I-29 gusts of 15-25 mph are expected, and east of I-29 gusts will be around 15 mph or less. Winds will remain on the gusty side overnight as cyclogenesis slowly begins to work its way east.

A warm front associated with this feature will drape from eastern Wyoming, through western South Dakota and southeast into Nebraska and southern Iowa. As an upper shortwave works through the pattern the front will move north into southeastern South Dakota. As it does so low chances (<25%) for isolated showers and thunderstorms are possible Saturday evening and overnight for areas along and south of Highway 20. Moderate instability of 1000-1500 J/kg will be present, but lapse rates of less than 6 deg C/km and 0-6 km bulk shear of less than 20 kts are not supportive of severe weather. However, some thunderstorms could still produce wind gusts of 45 mph. Showers may linger into Sunday morning. As far as totals are concerned, they should be very light. Ensemble guidance indicates only around a 35% probability of measurable rain (0.01").

DISCUSSION

Issued at 245 PM CDT Fri Jun 5 2026

Storms have developed over far western Minnesota and are moving east-southeast this afternoon. This activity is associated with an upper wave that will be moving across the northern Midwest into the Great Lakes region through tonight. With the better upper level support off to our northeast, the chance for thunderstorms is low and the chance for severe weather is even lower in our southwest Minnesota counties. If a storm were to sneak in (<20% chance), then it will have around 1,000 to 1,500 J/kg of MLCAPE and around 35-40 kts of shear to work with, which could support an isolated 60 mph wind gust or instance of half dollar hail. The main time frame for this highly conditional threat is through 9-10 pm.

Otherwise, tonight will feature mainly clear skies with calm winds, and thus patchy fog will be possible in spots. The NBM favors areas near and east of I-29 for fog while the REFS favors north of I-90. Would lean towards REFS on this one as there is plenty of moisture north of I-90 left behind from recent thunderstorms and these areas will cool the fastest towards the dew point tonight. Clouds may also linger longer near and south of Highway 20 as well tonight associated with storms to our south, so this could limit fog potential there. Speaking of those storms, they look to develop over eastern Nebraska and southwestern Iowa through the evening hours, but this is expected to remain south of the area through tonight. One thing worth watching with these storms is any potential outflow boundaries that are left behind that could affect weather for Saturday. Some CAMs including the 05.12Z HRRR and RRFS-2 show some storms developing over the Highway-20 corridor tomorrow afternoon and evening, perhaps associated with one of these potential boundaries lifting northward into our area, so that will be something to watch. But when looking at overall chances according to the REFS and HREF, the chance of rain is less than 20%. So otherwise, dry, sunny, and very warm weather is expected on Saturday, and with ridging aloft, look for highs in the upper 80s to lower 90s, hottest along the Missouri River Valley.

On Sunday, guidance shows and upper low moving north across the central Plains. To the west, a surface low will drag a cold front into western South Dakota. The EC Ensemble shows an up to 60% chance of measurable precipitation as early as Sunday morning over northwest Iowa associated with aforementioned upper low but most other guidance brings better rain chances into the afternoon. Cloud cover ahead of this system will mean poor destabilization ahead of any thunderstorms over northwest Iowa, so the severe weather threat potential looks low at this time. The cold front off to our west will help fire off strong to severe storms over the northern High Plains Sunday afternoon/evening, and some of these will try to push into areas west of I-29 into early Monday morning. However, waning instability and storms potentially outrunning the best shear will mean the chances for severe weather locally with this is also fairly low at this time.

The main story heading into the next work week will be the building heat, starting Tuesday. That's when highs look to climb into the 90s area-wide, with the potential for highs nearing 100 along the Missouri River Valley. Then Wednesday may be even hotter as a front turns winds more southwesterly in south- central South Dakota. The NBM has come down a little bit in temperatures, but looking at the LREF, it has a 30-50% chance of highs above 95 in south-central South Dakota and then a 40-70% chance on Wednesday in that area. One limiting factor to this heat being realized on Wednesday is that storms may form along and ahead of the front and so that could affect heating. Either way, keep up to date with the latest forecast and be prepared to take heat related safety measures!

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 1058 PM CDT Fri Jun 5 2026

VFR conditions are expected to prevail this period. Mostly clear skies and light and variable winds will allow for patchy dense fog formation. Though the best chances look to be near and east of I-29, low laying areas and river bottoms may also see development. Fog should burn off by mid-morning.

Winds will become southeast through the morning and increase. Areas west of I-29 will see gusts ranging from 15 kts to 30 kts, with the strongest over south central South Dakota. East of I-29 gusts will be less than 15 kts. Gusty winds continue through the end of the period.

FSD WATCHES/WARNINGS/ADVISORIES

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