textproduct: Sioux Falls

KEY MESSAGES

- Low stratus continues to dissipate through this afternoon.

- Moderate to high confidence in fog redeveloping tonight across much of the region. It may be dense at times resulting in visibility reductions to less than 3 miles at time.

- Potentially strong to severe thunderstorms are possible Thursday evening into Friday morning, and again Friday afternoon and evening. Main threats with both rounds is hail the size of pennies to quarters, and possibly a wind gust of 60+ mph.

- Rain is expected to transition to a wintry mix before becoming all snow overnight Friday. Snow tapers off my mid-morning Saturday.

DISCUSSION

Issued at 204 PM CST Wed Mar 4 2026

Stratus is expected to linger for areas east of I-29 late this afternoon and evening. This will likely work to limit our afternoon highs in that area. Have adjusted them down slightly with a blend of NBM and CONSShort. Overnight weak moisture advection on light southerly to southeasterly winds may result in another round of patchy dense fog. Most guidance keeps fog roughly east of the James River. However, some soundings indicate patchy fog may be possible as far west as central South Dakota. Will monitor conditions to see if any headlines are needed.

Tonight a low pressure system skirts to our southeast. While the main area of forcing and rain will be well south of our region, a weak band of positive vorticity advection and WAA may be enough to trigger light sprinkles to light rain over portions of northwestern Iowa and southwestern Minnesota. Confidence in sprinkles is low due to a wide variance in track of the system. Used a blend of NBM and HRRR to get mention of sprinkles into the forecast. Very little accumulation is expected, enough to wet the sidewalk up to a tenth of an inch. Overnight lows will fall to the mid 30s.

For the rest of Thursday expect partly sunny skies and breezy southeasterly winds. Gusts west of I-29 will peak in the afternoon around 25-35 mph, with slightly lower gusts of 20-25 mph expected to the east. Highs will be warm in the upper 50s to 60s. This coupled with the gusty winds will result in areas of central to eastern South dakota and Nebraska experiencing High to Very High Grassland Fire Danger. The good news is minimum relative humidity values will remain above critical thresholds, in the upper 30% or higher. The bad news is if a fire can start, the winds could rapidly accelerate fire through the dry grasses and field stubble. Please use caution with sources of sparks.

In addition, through the day Thursday a deepening mid to upper level trough will progress east through the Rocky Mountains. As it exits out onto the central Plains rapid lee cyclogenesis will couple with an increasing LLJ to bring chances for convection to the region. The latest 12Z runs of the GFS, EU, CAN, and NAM all show this wave sweeping northeast through our region. Ahead of it lapse rates sharpen steeply and MUCAPE increases to between 500-800 J/kg. The 0- 6 km bulk shear has also increased to greater than 45 kts. Given these conditions, elevated strong to severe thunderstorms are possible along and south of I-90 early Friday morning. Primary threat will be hail to the size of pennies (3/4 inch) to quarters (1 inch). Though less of a concern wind gusts in excess of 60 mph are also possible. This threat is covered well by the SPC day 2 outlook.

Rain and thunderstorms remain in the forecast for the majority of the day Friday as a cold front moves through the region. As it does so winds become northerly and increase behind the front. Widespread gusts of 25-35 mph are expected with isolated gusts up to 40 mph possible. Convective parameter's increase through the afternoon and by Friday evening another round of strong to severe thunderstorms is possible. The question with this second round is location of the most favorable conditions. While the track of the storm is fairly consistent across guidance, the location of the best forcing varies from I-29 to the southeast, to southeast of Highway 60. Main threat again will be penny to quarter sized hail with 60+ mph gusts possible. This round is highlighted in the SPC day 3 outlook.

From here guidance begins to diverge on the evolution of the wave. The GFS has the mid-level wave wrapping tightly into a closed low that cuts through the heart of our region. The EU, CAN, and NAM maintain an open wave. All indicate a period of transition on the backside from rain to a wintry mix to all snow late Friday night into early Saturday morning. The GFS indicates a potentially significant band of snow, while the others indicate accumulating snow, but to a much lesser extent. At this time uncertainty is too high to speculate on totals, however confidence is high that most of the region will see at least some accumulating snow. While winds overnight will decrease they will continue to gust 20-30 mph during the period when snow is expected to be falling. Some reductions in visibility due to blowing and drifting snow are possible.

The system is expected to exit northeast of the region by late morning Saturday. Clouds will decrease and highs will warm into the 40s. For Sunday winds will gradually become southwesterly ushering in a much drier air mass and warmer temperatures. Highs will climb into the 60s with a few 70s possible. Monday will be similar with even more WAA increasing afternoon highs into the 60s and 70s along and south of Highway 20. Monday afternoon a cold front moves through the region turning winds northerly and bringing periodic chances for rain and snow through mid-week. Highs Tuesday will be in the 40s and 50s, while Wednesday they will fall into the 30s.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 526 PM CST Wed Mar 4 2026

Latest satellite shows MVFR stratus sitting along and east of I-29 late this afternoon. This stratus will continue to sit over this area and will gradually expand to the west. At the same time, fog remains possible tonight as well. Some uncertainty remain in how expansive the fog will be so have continued with MVFR mist at this time. Fog will be included in TAFs when confidence increases in the development and expansiveness of it. Any fog that does form will burn off during the morning hours tomorrow. Winds will strengthen by the afternoon timeframe with southeast winds gusts up to 15-30 knots, strongest west of I-29, to end the TAF period.

FSD WATCHES/WARNINGS/ADVISORIES

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