textproduct: Sioux Falls

KEY MESSAGES

- Isolated to scattered showers and thunderstorms are possible for the rest of the evening for areas along and north of I-90. Severe weather is not anticipated, however some stronger storms may produce wind gusts to 30-40 mph and brief heavy downpours.

- A second round of isolated to scattered showers and thunderstorms are possible between 6 am to 10 am Saturday morning for areas around highway-20 in northwest Iowa. Low end severe storms are possible with large hail up to half dollar size.

- 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.

UPDATE

Issued at 910 PM CDT Fri Jun 12 2026

Showers and a few thunderstorms continue to push east across the area this evening. This is for locations mainly along and north of I- 90. Severe storms are not expected but lightning and brief gusty winds up to 30-40 mph. These showers will continue to weaken through the rest of the evening hours. This will leave a short period through part of the overnight hours where dry conditions are expected. However, another weak shortwave trough will push into the area late tonight. This will strengthen the low level jet (LLJ), resulting in warm and moisture advection aloft. This will increase instability values up to about 1,500 J/kg. Effective shear values look to reach up to about 40 knots as well. This will support a low end severe weather threat late tonight into early tomorrow morning across parts of northwest Iowa. Locations along highway-20 have the highest chances to see strong to severe storms. Think large hail up to half dollars is possible in the strongest storms. The severe weather threat will end by about mid morning. However, trailing showers may persist through portions of northwest Iowa the rest of the morning and even the afternoon hours. Aside from rain chances, Saturday will be a seasonable day with high temperatures warming to the 70s to low 80s across the area. Northwest winds will gust up to 20-35 mph as well.

Sunday will be a dry day as high pressure pushes into the area from the northwest. High temperatures look to remain in the 70s while winds weaken with gusts only up to 20-25 mph in the afternoon. With broad troughing and northwest flow in place, the next appreciable chance for rain looks to come by the middle of next week. Details remain uncertain.

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 /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 639 PM CDT Fri Jun 12 2026

Showers have developed north of I-90 and west of I-29 late this afternoon. These showers are moving off to the east. Have included a TEMPO group in KHON's TAF but left out of KFSD's TAF. Trends will be monitored to see if a PROB30 group needs to be added to KFSD's TAF. These showers will dissipate over the course of the evening hours. However, dry conditions will be short lived as another round of showers and storms looks to develop late tonight into early tomorrow morning along the highway-20 corridor, including KSUX. These showers and storms will push eastwards through the rest of the morning hours. Once these showers and storm push east of the area, breezy northwest winds with gusts up to 15-30 knots will finish out the TAF period.

FSD WATCHES/WARNINGS/ADVISORIES

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