textproduct: Sioux Falls

KEY MESSAGES

- Isolated strong to severe storms remain possible into the late afternoon hours. Brief downburst winds of 50 to 60 mph will be possible over NW Iowa and adjacent SD/NE counties.

- Heavy rain will be the primary risk into the evening with rainfall rates of 1-3" per hour and local totals of 3-5" possible. A flood watch for flash flooding continues into late evening.

- Isolated strong to severe storms will again be possible late Monday afternoon into Tuesday morning. These risks may continue into NW Iowa Tuesday afternoon.

- Quiet but continued warm conditions are expected for the rest of the work week.

DISCUSSION

Issued at 1246 PM CDT Sun Sep 6 2026

THIS AFTERNOON: Strong convection continues to develop in areas along but mostly east of I-29 this afternoon. The area continues to reside in a moderately unstable environment, but lacks any meaningful shear and mid-lvl lapse rates. However, climatologically significant PWATs are in place, with enough DCAPE to suggest an increased risk for wet microbursts over the next 1-3 hours in a narrow corridor from Madison to Sioux Falls, Sioux Center, Cherokee, Storm Lake, Le Mars, and Sioux City. Rainfall may be the most impactful hazard this afternoon with 1-2 hr totals of 3-4" already in portions of southern Minnesota. Additional convection is likely to continue to produce 2-4" totals in pockets of NW Iowa, though cold pool development may help push storms off an area before extreme values may be produced. The stronger MCV will also nudge it's way northward later this afternoon, and may work to produce additional northward/northeastward convection with it.

TONIGHT: This shortwave/MCV will drag it's feet eastward this evening, with some expected weakening of convection with the lost of daytime heating and general stabilization of the environment nearby. However, an increased LLJ may begin to develop after 02Z which could bring returning elevated showers and isolated thunderstorms to the CWA late this evening and continuing into the overnight hours. This activity will likely not be severe, but any shower could still bring brief heavy rain.

MONDAY-TUESDAY: Elevated shower activity diminishes towards daybreak as shortwave ridging arrives. An ejecting trough out of the Rockies will bring additional elevated convection into central and northern South Dakota into Monday afternoon, perhaps grazing the western CWA. As the EML gradually erodes into south central SD late in the afternoon, a few strong to severe storms may develop and track east southeast into the early overnight hours. As the LLJ increases after dark, elevated convection may expand in coverage with continued low- end severe weather risks for Tuesday morning.

More uncertainty for Tuesday, which is focused moreso on the location of the surface front and impacts of overnight elevated convection. While the primary surface front settles in northwest Iowa, a secondary stronger dew point gradient arrives later in the afternoon. Should sufficient clearing develop, then a storm or two could become stronger by mid-afternoon with activity quickly tracking southeast by the evening.

EXTENDED: With ongoing convection, no forecast changes made to the extended as a temporarily reprieve from active weather develops. Temperatures may still remain near to above normal for the rest of the work week.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1219 PM CDT Sun Sep 6 2026

Scattered convection will continue to develop early this afternoon, and continue into early evening. In thunderstorms, brief 40 to 60 mph wind will be possible, along with small hail, and torrential rainfall. The coverage near the TAF sites remains fairly uncertain, and impacts may be brief if they take place.

Scattered showers and isolated thunderstorms continue south of I-90 into the evening and early overnight hours. Again, brief reduction to MVFR or IFR conditions are possible, but will be driving by any sporadic updraft that passes through. Coverage in SUX high enough to include prevailing wording ATTM.

VFR conditions may fall to MVFR levels into Monday morning, though significant uncertainty remains as far as any stratus development.

FSD WATCHES/WARNINGS/ADVISORIES

SD...Flood Watch until 10 PM CDT this evening for SDZ062-067-071. MN...Flood Watch until 10 PM CDT this evening for MNZ080-081-089- 090-097-098. IA...Flood Watch until 10 PM CDT this evening for IAZ001>003- 012>014-020>022-031-032. NE...None.