textproduct: Sioux Falls

KEY MESSAGES

- Late tonight into early Thursday morning showers and thunderstorms are expected to develop across the region. Storms will move east through early afternoon Thursday.

- A few strong to severe storms may develop early Thursday morning (5-9 am). Wind gusts to 65 mph and hail up to ping pong ball size would be the main threats. These storms look to mainly track along I-80 but there remains the possibility that they could push up to and near the highway-20 corridor.

- Friday through the first half of next week will see cooler highs in the 70s to 80s and lower relative humidity values.

- Saturday will see a chance of thunderstorms over mainly northwest Iowa. At this time severe risk appears to be low.

UPDATE

Issued at 924 PM CDT Wed Jun 10 2026

Quiet conditions continue across the area this evening. Convection has developed on a cold front stretching all the way from northern Minnesota down through Iowa, southeast Nebraska, and Kansas. This current convection will push off to the east over the coming hours. This boundary is not done yet though as another shortwave trough currently over Wyoming will dive to the southeast. This mass response to this wave will strengthen the low level jet (LLJ) and begin to retreat this boundary northwards. This boundary will bring much greater moisture and instability along and north of I-80 and potentially reaching up to about highway-20 or so. Latest CAMs show convection developing just ahead of this surface front initially. With broad southwest to northeast flow in place, these new storms will push off to the northeast while the front continues to return northwards, allowing for a transition from elevated storms to surface based storms to take place. A mesoscale convective system (MCS) is possible. This environment will be characterized by large buoyancy with instability values up to around 3,000 J/kg and effective shear values potentially up to about 80 knots. This environment will be conducive for large hail up to ping pong ball size and damaging winds to 65 mph. The main uncertainty regarding these storms is precisely where they will track. Latest hi-res guidance is in decent agreement that these storms will track near I- 80. However, there remains the potential that these storms could reach up to about highway-20 late tonight into early tomorrow morning, roughly between 5 am to 9 am. Do think that the hi-res models are in the right ball park with the severe storms staying just south of the forecast area. Trends will be monitored through the night as a shift back to the north is possible.

Thursday will be a cooler day with high temperatures remaining in the 70s as stratiform rain will overspread the area for most of the morning hours before exiting the forecast area during the afternoon timeframe. A stray shower or two is possible for the rest of the afternoon timeframe. Rainfall amounts look to be light with amounts between a few hundredths to a tenth or two. Rainfall amounts that could exceed a quarter of an inch will be associated with weak thundershowers that may develop within the overall stratiform rain area. Winds remain on track to strengthen behind the departing system with gusts up to 30-40 mph. The strongest winds look to occur west of I-29, especially over central and south central South Dakota.

Friday continues to look dry with highs warming back to the 80s to low 90s. The next chance for showers and storms looks to return on Saturday, with the highest chances (20-40%) across parts of northwest Iowa.

DISCUSSION

Issued at 147 PM CDT Wed Jun 10 2026

A cold front draped from central Canada south through the central Plains will gradually make its way east through the afternoon today. To the east of the front an influx of moisture advection will work to destabilize the atmosphere. As the upper wave passes over the cold front it will work as a focus for shower and thunderstorm initiation. Short term guidance is in fairly good agreement that any stronger storms will be well east of the region into central Iowa this afternoon and evening, where the better dynamic setup is. One thing to watch this afternoon is a band of vorticity advection and enhanced stretching potential that could result in brief funnels late this afternoon for areas along and east of Highway 60. If any funnels form they should be weak and short lived.

Late Wednesday night into early Thursday morning an area of weak WWA coupled with an increasing LLJ swings through central South Dakota. This may trigger showers and thunderstorms. These storms will progress northeast through early Thursday afternoon. Instability is low, less than 500 J/kg, but could be enough for a few lightning strikes. For areas north of Highway 18, severe weather is not anticipated, however a few brief, heavy downpours are possible. Around daybreak a surface low will move northeast out of central Nebraska. Instability will rapidly increase ahead of the low as 0-6 km Bulk shear ramps up 70-75 kts. In addition, synoptic support in the form of a jet streak right entrance region, a mid-level trough axis, and continued intensification of the LLJ may work to focus storms into a more organized area of supercells. These will then quickly grow upscale into a mesoscale convective system (MCS). There remains some uncertainty in the track of the low, with most guidance keeping the initial stronger supercells just to the south of our CWA. However, a few bring isolated strong to severe supercells into our northeast Nebraska counties and into northwest Iowa, mostly east of Highway 60. These stronger storms will be capable of producing hail to ping-pong balls and wind gusts of 65 mph. As the strongest storms are expected during the morning commute, roughly 6 - 9 am, we will need to monitor the trends. Any lingering showers and thunderstorms should be east of the CWA by the early afternoon. Highs Thursday afternoon will be cooler thanks to CAA behind the wave, in the 70s.

Mostly zonal flow aloft and dry conditions are expected for Friday. At the surface west winds become southerly through the day. A strong push of WAA will warm afternoon highs in to the 80s and 90s. Friday overnight a weak cold front pushes through the region, brining low chances (<25%) of rain to areas along and north of Highway 14. As the front progresses to the southeast there will be additional low to medium chances (<40%) for light rain over portions of southeast South Dakota, northeast Nebraska, and northwest Iowa from roughly daybreak through the afternoon. Highs Saturday will be slightly cooler in the upper 70s to mid-80s. Northwesterly flow in the mid- levels keep cooler temperatures in the forecast for Sunday as well, with highs in the low to mid 70s. This trend of 70s for highs continues into the first half of next week. Dew points during this time will also be lower, in the 40s to low 50s. If you have any outdoor projects, this would be a great time to work on them without the heat and humidity.

Monday night into Tuesday a strong upper wave will work through the region bringing chances of rain to the area. Details on instability and potential for strong storms are uncertain at this time.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 1233 AM CDT Thu Jun 11 2026

VFR conditions begin the TAF period. Latest satellite shows mid and upper level clouds beginning to expand into the area from the west. The low levels remain dry but radar is beginning to pick up some returns. Expect to see rain develop and become more widespread through the overnight hours. Thunderstorms remain possible along and south of highway-20 late tonight into tomorrow morning. Confidence is still not high enough to include mention in KSUX's TAF but trends will be monitored. Rain will persist through the morning hours before pushing east of the area by the mid afternoon timeframe. Ceilings look to remain mainly VFR with visibilities dropping to MVFR levels. Once the rain pushes east of the area, VFR conditions will return to the area with winds strengthening out of the northwest. Gusts up to 20-35 knots is expected for the back half of the afternoon hours, strongest towards south central South Dakota. The northwest winds will be weakening tomorrow evening to end the TAF period.

FSD WATCHES/WARNINGS/ADVISORIES

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