Marine Weather and Tide Forecast for Vermillion, SD

UPDATE
Issued at 839 PM CST Fri Nov 6 2026

High level clouds continue to push west to east across the area this evening as a weak upper wave moves through. The ground is already near saturated, so the slower cooling due to the cloud cover won't be enough to prevent fog from developing through the overnight hours. Already seeing some light fog in a few spots in northwest Iowa, but look for this to expand and develop elsewhere especially after midnight to 2 am. Fog will likely be locally dense, so be sure to use extra caution on the roads if you have any Saturday morning plans. Fog may linger through much of the morning hours, with the last of the fog likely lifting not until the 10:30 am to noon time frame.

Temperatures are currently down into the low to mid 30s, but cloud cover and fog should keep temperatures from falling to the 20s for the most part outside of maybe one or two spots north of I-90. Road temperatures are above freezing across southwest Minnesota and northwest Iowa where there are sensors, and road temperatures in South Dakota are likely similar. Thus, road impacts from freezing fog appear low at this time, though vehicle windshields will likely be covered in frost. There could also be very light icing on elevated surfaces such as tree branches if the fog can become dense for a couple of hours wherever temperatures are below freezing. So outside of perhaps a very isolated patch of ice on a bridge or overpass, slick driving conditions are not anticipated. Of course, some of the precautions for driving in fog are similar to ice anyway: leave plenty of space between you and the car in front of you and maintain safe driving speeds for the conditions.

The morning fog should lift and become low stratus through at least the early afternoon, but this will likely scatter out during the afternoon hours as winds in the stratus layer begin to turn more westerly to slightly northwesterly. The exception will be over parts of northwest Iowa where low level moisture may linger and thus do generally expect these areas to have the coldest high temperatures tomorrow afternoon (upper 40s to low 50s) as it remains under mostly cloudy skies. The rest of the area will see highs in the low to middle 50s, though south- central South Dakota where morning fog/stratus is likely to be more limited will see afternoon highs rise into the upper 50s and potentially the lower 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 /00Z TAFS THROUGH 00Z SUNDAY/
Issued at 550 PM CST Fri Nov 6 2026

Mainly VFR conditions for the first few hours of the period, though low stratus will make a return along with some areas of fog through the overnight hours. Locally dense fog is expected, though some uncertainty remains as to how widespread any dense fog will be.
Still, most areas that see fog will have visibilities reduced at least below 1-2 miles by daybreak Saturday. Fog should lift by the mid morning, but will transition to IFR stratus. This stratus should scatter out during the afternoon as winds turn more west/northwesterly within this stratus layer, though some uncertainty remains as to how fast this stratus deck will clear.

Winds will be mainly light and variable tonight, then staying light but mostly out of the southwesterly direction during the daytime Saturday. Winds during the day on Saturday will generally be sustained around 5-10 kts, with perhaps a gust of two up to 20 kts near and north of Highway 14 in the afternoon.

FSD WATCHES/WARNINGS/ADVISORIES
SD...None.
MN...None.
IA...None.
NE...None.