textproduct: Sioux Falls

KEY MESSAGES

- Isolated to scattered showers and thunderstorms are possible late this afternoon and into the evening for areas along and south of Highway 14. Severe weather is not anticipated, however some stronger storms may produce wind gusts to 45 mph and brief heavy downpours.

- A second round of isolated to scattered showers and thunderstorms are possible beginning around daybreak Saturday for areas along and north of Highway 18 and east into northwest Iowa. Severe weather is not expected, but some storms may produce wind gusts to 45 mph, brief heavy downpours, and possibly some small hail.

- Seasonably cool conditions are expected for this weekend and into the first half of next week. Highs will be mainly in the 70s to low 80s with low relative humidity.

DISCUSSION

Issued at 155 PM CDT Fri Jun 12 2026

Mostly clear skies, WAA on breezy southwest winds, and deep mixing will help our high temperatures this afternoon warm into the 80s. Looking aloft we see a strong upper low over eastern Canada. A cold front drapes southwest through northern Minnesota, through North Dakota, and into Montana. This front will drift southeast bringing chances for showers and thunderstorms with it. As the front approaches our western border this evening, an area of surface convergence will form ahead of it. Increases in low- level Theta-e contributes to a modest increase in instability, though MUCAPE remains on the low side, around 500-800 J/kg. At the same time mid-level lapse rates increase, and 0-6 km bulk shear will be in the 50 kt range. While severe weather is not anticipated, the stronger shear could allow a few isolated updrafts to organize enough to produce small hail. Though, with cloud base heights of 8000-10,000+ ft AGL the chances small hail will survive to the surface is low. Tall, skinny CAPE profiles on soundings indicate that some brief heavy downpours are possible. Soundings also indicate a deep, very dry subcloud layer. Evaporational cooling could result in wind gusts to 45 mph, and is the most likely threat with any stronger storms. Convection is expected to begin as a weak mid- level short wave intersects the front around 6-8 pm. The strongest storms are expected along the Highway 14 corridor from roughly Huron east into Minnesota. Weaker, more showery storms may drift as far south as I-90. Storms should be east of the CWA around midnight.

As the cold front continues to progress southeast through the overnight, another surface low and attendant warm front will be moving northeast out of Colorado/Wyoming. Between the two fronts will be a slightly stronger area of convergence. Similar to Friday evening, instability increases as an area of rich Theta-e moves north into the region. Mid-level lapse rates increase into the favorable range for stronger storms, as well as bulk shear at 40-50 kts. However, several questions remain. First, the environment is strongly capped, for storms to form they will have to fire along the 925 mb front. The second question is how far north the richer Theta- e air will advect. The CAN and NAM12 have higher values working into the area as far north as Highway 18 and east into northwest Iowa, while the GFS and EC are more conservative and higher values remaining south of Highway 20. Third, when will the mid- to upper wave arrive? There is enough variance in guidance to leave confidence in strong storm formation low (10%). Enough forcing looks to be present to initiate isolated to scattered elevated showers and thunderstorms. The main threat will again be wind gusts to 45 mph and brief heavy downpours. Unlike Friday, the cloud base heights are around 900 ft AGL. So while small hail is still unlikely, it has a better chance surviving to the surface should it form. Any stronger storms are most likely to occur as convection initiation begins around daybreak, 5-7 am. Storms will weaken and gradually move east through the early afternoon Saturday.

Behind the cold front, winds will become northwesterly and cooler air will flow into the region. Highs for Saturday will depend on where you are within the CWA. For those north of I-90 low to mid 70s are expected. To the south, mid to upper 70s. Clear skies Sunday with a couple of dry short waves reinforcing the CAA limit highs to the low to mid 70s. Monday a return to westerly flow and mostly sunny skies will bring highs back into the mid 70s to low 80s. Monday evening a stronger shortwave will work through the pattern, bringing chances for showers and thunderstorms. While some thunder is possible, severe weather is not anticipated at this time. Tuesday will be mostly sunny with a stronger push of WAA. Highs will be in the mid 70s to mid 80s along the Missouri River Valley. Highs for the second half of the week will remain in the 70s and 80s for the most part. From here guidance begins to diverge. Multiple chances for showers and storms exist, though details are uncertain at this time. One final note: Those with outdoor plans, rejoice! This weekend through the first half of next week will not only be on the cool side of average for this time of year, but relative humidity values will also be low. Get out and enjoy the pleasant weather!

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1259 PM CDT Fri Jun 12 2026

VFR conditions are expected to prevail for the majority of the period. Winds will become southwest behind a cold front that is approaching from the northwest. Afternoon gusts of 20-30 kts are expected for areas west of I-29, 15-20 kts to the east. Winds generally decrease to light and variable after sunset. Areas along the Missouri River Valley will continue to gust 15-20 kts through roughly midnight before becoming light and variable. Winds become northerly and increase around daybreak, gusting 20-30 kts, with the highest gusts over south central South Dakota.

Chances for showers and thunderstorms begin for areas north of I-90 late this afternoon into the evening. Severe weather is not expected, but some storms could be marginally strong and produce wind gusts to 45 mph, and brief heavy downpours. Possibly some small hail as well but confidence in hail is low. The area most likely to see marginally strong storms will be along Highway 14 from roughly Huron east into Minnesota. Storms clear east shortly after midnight. A second round of showers and thunderstorms are possible around daybreak on Saturday, this time along and south of Highway 18. Similar conditions are expected, wind gusts to 45 mph, brief heavy downpours, and possibly small hail. These storms linger in northwest Iowa through the end of the period.

Finally, LLWS is expected as the previously mentioned cold front moves through the region beginning around midnight from roughly Wagner, South Dakota northeast to Pipestone, Minnesota and southeast. At first shear will be a directional hazard, but as boundary layer winds become light and variable speed shear will also become a hazard. The area of shear will track with the front to the southeast through roughly daybreak Saturday.

FSD WATCHES/WARNINGS/ADVISORIES

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