textproduct: Sioux Falls

KEY MESSAGES

- Elevated to critical fire danger is expected on Sunday. A Red Flag Warning has been issued for locations along and west of the James River where confidence is highest in critical fire danger conditions being met. The Warning is in effect from noon to 7 pm Sunday.

- Showers and storms remain in the forecast for the weekend. Chances for storms remains low (15-30%) with locations across northwest Iowa having the highest chances for seeing rain. A strong to severe storm is possible.

- Monday brings the best chances (30-60%) for strong to severe storms. However, there remain uncertainty regarding the location in where storms develop. Continue to check the forecast for the latest updates.

- Chances (30-50%) for showers and storms look to persist through the rest of the week. Details remain uncertain at this time.

DISCUSSION

Issued at 300 PM CDT Sat Apr 11 2026

Warm advective rain showers have pushed off to the east this afternoon. However, moist low levels has kept low level stratus around. This has kept high temperatures in the mid 40s to mid 60s, warmest across south central South Dakota. This is due to winds taking on a south/southwest component across south central South Dakota, resulting in clearing the stratus across this area. Breezy winds will be persistent though and last through the overnight hours. With breezy winds and stratus in place, only have low temperatures falling to the 50s across the area. There remains the possibility of a rouge storm or two late tonight. Should a storm develop, it would be across parts of northwest Iowa. This seems unlikely (15% chance) as of now as warm air advection (WAA) strengthen aloft without advecting sufficient moisture with it. This will lead to an increasing cap above the moist stable later. If a storm can form, then it would have the potential to be strong to severe given sufficient

Low level winds will turn westerly for the day tomorrow and remain breezy. High temperatures look to significantly warm into the upper 70s and and low 80s across the area. With drier westerly flow in place, humidity levels will drop, resulting in critical fire danger being reached. More details can be found in the fire weather discussion below. The westerly winds will advect drier air into the area throughout the day. However, guidance is persistent in showing this drier air shoving the better low level moisture all the way down to portions of northwest Iowa. This moisture boundary would be the location for a rouge storm to develop on. However, a weak shortwave trough will already be east of the area, promoting subsidence on its backside. Thus, Sunday looks to be mostly dry though there remains the outside chance (15-30%) that a few showers or storms develop along and southeast of this boundary. Any fire danger will come to an end during the evening hours as the boundary layer stabilizes. WAA will restrengthen aloft ahead of an incoming exit region of an upper level jet tied to a shortwave trough. Moisture looks scarce above 900mb and with the WAA strengthening the low level inversion. Again, the potential for any showers remains low at 15% or less through the night. If a storm is able to form, it could be strong to severe. Low temperatures will fall to the 40s and 50s overnight.

Monday looks to have the highest chances for strong to severe storms as medium range guidance is in decent agreement in a shortwave trough pushing through the Northern Plains. The mass response to this wave will result in southerly return flow and moisten dew points across the forecast area. With mid level lapse rates to above 8C/KM aloft. This will result in the potential for large buoyancy. There remains some uncertainty though as some of the guidance shows the bulk of the moisture getting advected to the east of the area. This possibility would happen if the surface low races east of the area and and introduces westerly surface winds on its back side. If the incoming shortwave is slower aloft, then the surface low will not quickly race off to the east and thus leave a broader warm sector across the area. The other component to potential severe weather is the cap. Latest guidance continues to support a strong cap above the warm sector. At this time, the longer range CAMs such as the RRFS, NAM3km, and FV3 do show convection firing along the warm front. But, this front is just north of the area. With the mean wind remaining out of the southwest, these storms would quickly push off to the northeast. Latest REFS also suggests this solution as well as convergence is strongest along the warm front north of the forecast area. As of now, only the deterministic Euro, Euro ensemble, and AIFS (AI Euro) show the warm front remaining draped across I-90 and thus producing convection Monday afternoon. Think the current SPC Day 3 outlook remains valid given this remaining uncertainty.

The warm sector looks get shoved further south and east of the forecast area on Tuesday. While the main wave will eject out of the Rockies on this day, keeping severe storm chances around. If the boundary remains off to the south and east, then storms chances would be lower. If the boundary remains across the forecast area, then storm chances would increase across the area. Tough to say which solution is correct at this time but something to keep an eye on over the next few days. The upper level pattern diverges towards the middle and end of next week but additional chances for showers and storms remain possible. Aside from rain chances, high temperatures look to remain above average in the 70s and 80s through Friday.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 644 PM CDT Sat Apr 11 2026

A mix of VFR down to LIFR across the region this evening due to layer of lingering stratus from roughly the James River and east. Clouds are expected to lift and thin through the overnight hours becoming scattered to clear with VFR ceilings shortly after sunrise. There is a low chance, < 25%, for light showers to drizzle to form after midnight. However, confidence is too low to include at this time.

Breezy southeast winds gusting 20-25 kts will continue through the overnight. Around sunrise winds will turn southwest as low pressure passes through eastern North Dakota. Winds will ease briefly while changing directions but then increase again to gusts of 20-25 kts.

FIRE WEATHER

Issued at 300 PM CDT Sat Apr 11 2026

Temperatures are expected to warm to the the upper 70s and low 80s across the area tomorrow. Dew points will lower to the 30s and 40s for most locations outside of northwest Iowa. This will result in humidity values down to 15-35%, lowest across south central South Dakota. Winds will be strongest in the morning but remain breezy with gusts up to 30 mph through the daylight hours. There remains some uncertainty regarding the dryness of available fuels across the area due to today's morning showers and lingering drizzle. Although low level winds are expected to turn westerly by tomorrow morning, pushing today's low level stratus out of the area. Confidence is higher in this possibility (~60%+ chance). However, if the stratus does not clear as quickly as currently expected, then temperatures will be cooler and thus humidity will be higher. As of now, have issued a Red Flag Warning for locations along and west of the James River where confidence is highest in critical fire danger conditions being met. The Warning is in effect from noon to 7 pm. Expansions to the Warning is possible.

FSD WATCHES/WARNINGS/ADVISORIES

SD...Red Flag Warning from noon to 7 PM CDT Sunday for SDZ050-052- 053-057>060-063>065-068-069. MN...None. IA...None. NE...None.