textproduct: Sioux Falls

KEY MESSAGES

- Areas of fog may expand further early this morning. Patchy dense fog will drop visibilities to under one mile at times, but confidence is low in dense fog becoming widespread. Visibility should improve late this morning.

- Expect slightly warmer weather this weekend with highs returning to the 50s to mid 60s. Lingering cloud cover over parts of northwest Iowa may bring highs only into the 40s today.

- Slightly warmer than normal temperatures persist today through Wednesday. The next low chance of rain comes for some on Wednesday. Otherwise dry weather is favored through the work week.

UPDATE

Issued at 435 AM CST Sat Nov 7 2026

Northwest flow aloft brought a break in passing cirrus early this morning with temperatures continuing to hover near the freezing mark, in the low 30s. Weak south winds behind departing sfc high pressure have kept widespread fog from developing. Surface observations and webcams as of 4am show an area of dense fog in central SD, from west of Huron southwestward toward Chamberlain and Platte. The HRRR and RRFS aren't doing well with capturing the current extent of fog but have held a trend of expanding fog (at times, dense) eastward into southeast SD early this morning. There's also potential for a second area of fog spreading northeast from northeast Nebraska into northwest IA/southeast SD around 5 to 8 AM, as a plume of higher moisture in the sfc-850mb layer advects in. With road/soil temperatures remaining near to above freezing, road impacts from freezing fog are unlikely, but elevated surfaces such as windshields and trees may see a coating of freezing fog. Will continue to monitor observational trends, but confidence is too low in widespread fog formation to issue an advisory at this time.

Models continue to suggest any morning fog will dissipate with mixing and/or lift to a low stratus deck late morning into early afternoon. As indicated previously, northwest Iowa may see prolonged stratus, keeping high temperatures in the 40s to near 50 degrees, colder than elsewhere. Upstream, enhanced mixing ahead of a prefrontal trough brings temperatures in south central SD warmer into the low to mid 60s.

DISCUSSION

Issued at 240 PM CST Fri Nov 6 2026

Low level stratus has begun to thin, becoming scattered to few this afternoon as slightly warmer, light winds aloft erode it from the top down. This evening and overnight an upper trough will pass through central Canada toward the Great Lakes region. This will drag a diffuse surface boundary and narrow band of slightly higher moisture through the region. Weak instability and WAA in the moist layer will likely result in low stratus formation after midnight tonight. Subsiding air aloft will work to lower the stratus to very near the surface. At the same time cooling surface temperatures approach the dew points and patchy dense fog may also form. The combination of low stratus/fog could result in visibility decreasing to 1 mile or less at times. REFS guidance indicates a medium probability of 50-70% in low visibility through mid-morning Saturday. There is a very low probability (<15%) of freezing fog, mostly north of I-90 where temperatures are projected to fall to or just below freezing. This could result in scattered slippery spots on roads. Please use caution and be prepared for rapidly changing road conditions. South of I-90 lows are expected to be in the low to mid 30s. There is some uncertainty with overnight lows due to uncertainty in stratus coverage and thickness. If it is very thin temperatures could be a degree or two colder than forecasted.

Clouds slowly dissipate Saturday morning as light but warmer south- southwesterly winds flow into the region. By Saturday afternoon partly to mostly sunny skies are expected as highs climb into the mid 50s to low 60s. Late Saturday afternoon into the evening a surface low located just southwest of the Hudson Bay will drag a cold front through the upper Plains. This will turn winds northwest for the overnight hours. Lows will fall to the mid to upper 30s. An upper ridge moves over the Plains during the day Sunday, turning winds to the south by the afternoon. Highs will climb into the 50s and low 60s.

Monday and through the middle of next week the pattern aloft will be "wavy". However, lack of moisture at the surface and midlevels keep the forecast dry. Highs will be warmest Monday in the low to mid 60s. Temperatures Tuesday through Thursday will be cooler in the 50s, but still above average for this time of year (upper 40s). Wednesday night into Thursday bring the next chance for precipitation, but details are vague at this time.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 1100 PM CST Fri Nov 6 2026

Patchy light fog has developed over parts of northwest Iowa so far tonight, but look for fog to grow in coverage as mid/high level clouds move east and out of the area. Fog may be dense at times around daybreak. Some guidance has backed off this potential for fog, but given observations to our west and a nearly saturated ground already, still thinking we should see fog development. Fog will lift by the late morning hours, marking the return of VFR conditions for the most part. Some lower stratus may linger over parts of northwest Iowa through Saturday afternoon and evening, though confidence is low on this potential.

Light winds continue through daybreak, with southwesterly winds picking up around 5-10 kts through the day on Saturday. Winds will gradually turn more west-northwesterly during the evening and early overnight hours as a weak cold front sweeps across the area from west to east.

FSD WATCHES/WARNINGS/ADVISORIES

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