textproduct: Sioux Falls

KEY MESSAGES

- Strong to severe storms are possible tomorrow. Some uncertainty remains but locations along and near highway-14 from Brookings, South Dakota to Marshall, Minnesota have the highest chances for seeing strong to severe storms. The main timeframe for severe weather is between 3 pm to 9 pm Monday. Continue to check the forecast for the most up to date information.

- Chances (20-60%) for showers and storms look to persist through the rest of the week. Details remain uncertain at this time.

UPDATE

Issued at 921 PM CDT Sun Apr 12 2026

Winds have become light and variable this evening. There is a low to moderate probability (30-40%) for patchy fog development over northwest Iowa early Monday morning. Brief reductions in visibility are possible down to around 2 miles. Please be prepared for changing conditions as you make your morning commute. Fog is expected to burn off by mid-morning.

Monday chances for showers and thunderstorms return to the forecast area. High temperatures will climb into the upper 70s to mid 80s. At the same time a plume of moisture will pool to the east of dryline that stretches south from a surface low pressure located on the borders of central South Dakota and Nebraska. This moisture advection aids in destabilization of the warm sector as the low gradually moves northeast through the day. Overall dynamic parameters are favorable for isolated to scattered strong to severe thunderstorms to develop Monday afternoon. However, a very strong cap will be in place through much of the day. Mixing will work to weaken the cap but will it be enough that a surface based parcel can break through? That is the main question and will have the most impact on storm evolution and threats. The most likely scenario is elevated thunderstorms begin to fire in the afternoon in east central South Dakota and southwestern Minnesota as the southwest to northeast oriented LLJ begins to ramp up along and east of I-29. The primary threat with these would be large hail up to 2 inches in diameter, and damaging wind gusts of 70 mph. These storms quickly move northeast of the forecast area. A second round of storms may be possible as a secondary west to east oriented LLJ forms over central South Dakota. As the jet interacts with the triple point, an isolated supercell or two is possible. Should these develop not only is large hail and damaging wind a threat, but a tornado or two cannot be ruled out. The area most likely to see this second round is along Highway 14 from roughly central South Dakota east into southwest Minnesota. As 00Z data has begun to flow in some of the CAMS guidance has begun to pick up on this development.

DISCUSSION

Issued at 243 PM CDT Sun Apr 12 2026

Fire danger persists this afternoon along and west of I-29. More details can be found in the fire weather discussion below. Breezy westerly winds persist with high temperatures warming to the 70s to low 80s, making for a warm April day. Fire danger will come to an end this evening as temperatures cool and winds weaken. Low temperatures will fall to the upper 40s and 50s overnight.

Winds will turn to out of the south/southeast on Monday, resulting in moist southerly flow and moistening dew points back into the 40s, 50s, and even low 60s. High temperatures will warm to the upper 70s and 80s across the area as a warm front pushes northwards. There remains uncertainty in where the warm front sets up. Some of the latest hi-res models bring the warm front to the vicinity of highway- 14. Some push the front just north of the highway while others are just south. This will have a big effect on any severe storm potential during the afternoon hours tomorrow. A stout elevated mixed layer (EML) will be in place. Sounding climatology would place this EML at the very top of climatology for this time of year! This EML will result in capping across the warm sector, limiting more widespread convective coverage. It could completely prohibit any storms from developing across the area though again that depends on where the warm front sets up. This uncertainty also extends to the location of the surface low tied to the warm front. Latest ensembles are in line with the latest hi-res guidance in lifting the surface low through the center of the forecast area. This would then turn surface winds to out of the west both within and behind the low. The westerly winds will advect much drier air into the area. This drier area will make for a much narrower warm sector with the best instability residing just along the warm front itself where moisture is still able to pool. CAPE values look to reach up to 1500 to 2000+ J/kg along the front in tandem with more than sufficient vertical shear in place thanks for an upper level jet sitting over the area. As of now, the best convergence along the warm front is along highway-14 from Brookings, South Dakota to Marshall, Minnesota. This looks to be the main area for convective development as sufficient low level moistening and convergence looks to be just enough to overcome the cap. Should storms develop, it looks to be a smaller number of storms, only about 1 to 3 storms. Thus, large hail up to 2 inches in diameter, 70 mph winds, and an isolated tornado is possible. The main timeframe for convection would be between 3 pm to 9 pm.

Tuesday will be a quieter day as Monday's boundary will be pushed off to the southeast. This will keep any instability along with strong to severe storm chances out of the area. However, there remains the potential for some light rain if a deformation zone can set up. Though if it does, any rainfall would be light at a tenth of an inch or less. Tuesday will also be slightly cooler with high temperatures in the upper 60s to upper 70s.

Chances for strong to severe storms look to continue through the rest of the week. Wednesday could be the next chance for severe weather as medium range guidance shows another wave pushing through the area. These models do show that this wave may close off which could bring a warm front further north, thus bringing more instability with it. As of now, the ensembles show the low staying south and east of the forecast area. Will still keep an eye on trends over the coming days in case the low comes north. As of now, high temperatures look to warm to the upper 60s to low 70s.

Thursday looks to be a quiet day as shortwave ridging pushes through the Plains. A stronger upper level wave looks to eject into the Plains on Friday. A stronger cold front will be tied to this wave. Severe storms could be possible along this front though currently medium range guidance shows the cold front either just about to fully pushing through the forecast area by Friday evening. This could preclude severe weather chances if the front pushes through the forecast area quickly. Something to keep an eye on as we progress through the week. Chances for precipitation could continue through Saturday before dry conditions return for Sunday.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 657 PM CDT Sun Apr 12 2026

VFR conditions are expected through the period. Gusty northwest winds are beginning to decrease this afternoon and will gradually become light and variable after sunset. There is a 30-40% chance of patchy fog development tonight focused over northwest Iowa, including KSUX. Visibility may drop to less than 2 miles at times. Fog is expected to burn off by mid-morning.

A few light showers are possible over central South Dakota early Monday morning, moving northeast through about daybreak. Confidence in showers forming is low, less than 20%, so have left them out of KHON at this time. As the day continues chances for thunderstorms increase (30-50%) for areas along and north of I-90, to include KFSD and KHON. A few of these storms could be strong to severe producing large hail (2+ inches) and wind gusts up to 70 mph. The area most likely to see severe storms is along Highway 14 in southwest Minnesota. While unlikely, a tornado in this area is possible. Storms will move northeast through the end of the TAF period.

FIRE WEATHER

Issued at 243 PM CDT Sun Apr 12 2026

Temperatures have warmed to the 70s to low 80s across the area. Dew points have lowered to the mid 30s to 40s across the majority of the area. The exception is locations across northwest Iowa and parts of southwest Minnesota where dew points have remained in the 50s to about 60F. Thus, humidity values have fallen to about 20-30% across the majority of the forecast area, excluding northwest Iowa and parts of southwest Minnesota. Winds remain westerly with gusts continuing to remain above 30 mph. Thus, critical fire danger conditions have been met. Have expanded the Red Flag Warning another row of counties north and east to account for the rest of the fire danger. The Red Flag Warning remain in effect until 7 pm this evening when cooling temperatures and weakening winds will end the fire danger.

Elevated fire danger remains possible tomorrow as low humidity is expected along the Missouri River Valley. However, winds will be much lighter as they turn from southeasterly to westerly with gusts only up to 15 to 25 mph. Thus, only high fire danger is expected.

FSD WATCHES/WARNINGS/ADVISORIES

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