Marine Weather and Tide Forecast for Vermillion, SD

UPDATE
Issued at 328 AM CDT Thu Apr 16 2026

More benign weather to start this Thursday, with temperatures in the upper 30s to lower 50s and clear skies over the area. Light winds at the time of this discussion will begin to increase toward daybreak and shift more to the southwest. Although a couple of sites are showing less than 10 SM of visibility, winds look to be just strong enough to prevent fog development.

Forecast remains on track today with very warm temperatures in the 80s and very low humidity. These factors combined with the breezy to strong southwesterly winds gusting to around 35 mph lead to near critical and critical fire conditions. Red Flag Warnings are in effect this afternoon and evening. More details in the Fire Weather section. Use extreme caution to prevent sparks and fire starts; fires will spread quickly today!

Breezy to gusty winds continue tonight as a cold front moves through into early Friday. Wind gusts of 30-40 mph expected. Temperatures fall back to below seasonal normals behind the cold front. Elevated fire danger continues Friday.

No change to the Day 2 SPC Outlook for severe weather potential, which shows a Marginal (level 1 of 5) risk for areas southeast of Ida Grove to Storm Lake. Confidence in storm development in our area is low (less than 30%) with most guidance already pushing the cold front through our area by late morning.

DISCUSSION
Issued at 220 PM CDT Wed Apr 15 2026

Strong to severe thunderstorms have stayed south and west of the area thus far today. Instability has been marginally supportive of at least some occasional rumbles of thunder today, and as we reach the peak of daytime heating, a few more hundred J/kg of CAPE will develop. This may lead to slightly better coverage of thunderstorms mainly south of a Sioux Rapids to Sioux City, IA line, but the chances for severe weather look quite low. There's still around 45-55 kts of bulk shear, so if a decent updraft can get going and sustain itself, then quarter sized hail cannot be ruled out.
This threat ends around 6 pm as storms move off to the east. Quiet weather expected tonight as the main upper wave responsible for the rain moves off to our east. Lows tonight drop to the middle 40s for the most part across the area by Thursday morning.

Winds start turning more southwesterly heading into the day on Thursday, which will help usher in warmer and drier air into the area and leading to critical fire weather conditions. More on this in the fire weather discussion below. For Thursday night into the day on Friday, a deep trough extending from the northern Rockies into the Four Corners will move through the area. At the surface, a strong cold front will sweep across the area during the day on Friday. By 1 pm on Friday, deterministic and ensemble guidance has the front either just east of the IA/MN Highway 60 corridor or just east of the forecast area. These faster solutions will limit the potential for severe weather in our area as the better instability would develop off to our east. So still a low confidence severe weather forecast, but a very isolated strong to severe storm still remains possible over parts- Very patchy of northwest Iowa and southwest Minnesota early Friday afternoon if the cold front slows down or a storm is able to develop just before the front clears the area.

Colder air will be rushing in behind the front as guidance is in good agreement of a strong push of cold air advection (CAA)
following the frontal passage on Friday. This means for most of the area, the morning will be warmer than the afternoon, so dress accordingly! With the colder air moving in, any precipitation leftover behind the frontal passage could turn to a wintry mix or snow as the system exits the area. Latest guidance is trending towards our area drying out before the coldest air arrives, limiting the chance for wintry weather. There is a potential where at least some rain could turn to wintry precipitation along portions of the Highway 14 corridor Friday morning/early afternoon, but this would likely be short-lived and thus cause little impacts. Still time for things to change, so be sure to keep up to date with the latest forecast! This push of CAA will also lead to windy conditions Friday into Saturday, with northwesterly gusts to 30 to 40 mph expected both days, strongest on Friday. Temperature-wise, look for lows down into the 20s to lower 30s Saturday morning and then the 20s area- wide by Sunday morning. Highs on Saturday will struggle to make it to the 50s for the most part, coolest east of the Missouri River.
Ridging aloft looks to build into the area heading into early next week, which will help bring about a warming trend with limited rain chances through the start of the next work week.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/
Issued at 621 AM CDT Thu Apr 16 2026

VFR conditions prevail through the period. May see some precipitation move into areas west of the James toward the end of the forecast period, but will omit for now given lower confidence.

Main focus for this TAF cycle is the winds. Light winds this morning quickly increase and shift southerly. We'll see gusts 25 to 30 knots by the afternoon and through the TAF period.
Direction today varies from south to southwest. As we head through tonight, a cold front moves from west to east across the area overnight into early Friday, with breezy winds shifting to northwest behind it. Some LLWS is expected as the winds shift, although conditions appear a bit more marginal in speed and direction toward I-29 at the end of the period. Only included mention at KHON for now.

FIRE WEATHER
Issued at 328 AM CDT Thu Apr 16 2026

Red Flag Warning has been expanded toward the US Hwy 59 corridor in southwestern MN and northwestern IA, now in effect from noon to 8 PM for most of the area. Areas in the Red Flag Warning have the highest confidence of minimum RH values at or below 25% and coincident southwest wind gusts around or above 25 mph. Further east, confidence is lower and duration of near to critical fire danger is shorter. Additionally, this area to the east has also seen the most precipitation over the last few days. Expansion east may be needed later today if we are drier and/or breezier than current forecast suggests. Extreme caution should be used today as any fire will likely spread quickly due to these strong winds and very low humidity values.

Winds tonight remain breezy with a shift through the overnight hours from more southerly to northwesterly as a cold front swings through the area. Northwesterly winds remain strong on Friday, with gusts around 35-40 mph (strongest in south central SD). Cooler and falling temperatures with early day precipitation chances should keep minimum RH values above 35%. That said, elevated to possibly near critical conditions are expected with the strong winds, which may be enough to overcome higher RH in areas which have not received as much precipitation or have seen as much green up over the last few days.

Breezy northwest winds remain in place Saturday gusting again 30-40 mph with temperatures near seasonal norms. Much drier air moves into the region though, which will plummet minimum RH values between 20 and 30% across the area. Again, elevated to near critical fire conditions are expected.

FSD WATCHES/WARNINGS/ADVISORIES
SD...Red Flag Warning from noon today to 8 PM CDT this evening for SDZ038>040-050-052>071.
MN...Red Flag Warning from noon today to 8 PM CDT this evening for MNZ071-072-080-089-097-098.
IA...Red Flag Warning from noon today to 8 PM CDT this evening for IAZ001-012-020-031.
NE...Red Flag Warning from noon today to 8 PM CDT this evening for NEZ013-014.