Marine Weather and Tide Forecast for Vermillion, SD

DISCUSSION
Issued at 337 PM CST Thu Mar 5 2026

Mid to upper clouds are building in ahead of an approaching wave this afternoon. Breezy southerly winds will gradually decrease through the evening. Lows for tonight will fall into the low 30s to mid 40s, with the warmest temperatures over northwestern Iowa.
Tonight WAA and an increasing LLJ may be enough to trigger showers and thunderstorms, most likely beginning after midnight. Some of these could be strong to severe with 500-1000 J/kg of tall and thin MUCAPE, and 40+ kts of 0-6 km bulk shear. ESAT tables indicate precipitable water to be at >99% for climatology from 06.06Z through 07.06Z. Considering this, rainfall could be heavy at times under stronger thunderstorms. By Friday morning rain totals of 0.2" to 0.4" are possible for eastern South Dakota with the highest as you move east. Areas in southwestern Minnesota and northwestern Iowa may see 0.5 to 0.75" in total. As far as the severe threat is concerned, despite some convective parameters being on the favorable side the weak instability may limit severe storms to just one or two isolated thunderstorms. The main threat with any that do become severe will be heavy rain, hail up to the size of a quarter (1 inch), and possibly wind gusts in excess of 60 mph. The main area of concern is for areas east of I-29 in northwestern Iowa and eastern Nebraska.
Severe risks diminish around daybreak Friday.

A surface low pressure will move through the region dragging a cold front with it early Friday morning. Strong CAA in the 925-850 mb layer rapidly decrease temperatures there 10-15 degrees C. This will help to bolster gusty northerly winds behind the front. Areas along and west of the James River Valley will experience the strongest gusts of 30-40 mph. Through the day stronger winds push east of I-29 but will be slightly lower at 20-30 mph. In addition rain showers and weak thunderstorms will become scattered to numerous through the day as the main vorticity lobe of the wave moves northeast. With this comes an increase in instability and renewed chances for strong to severe thunderstorms for areas east of I-29 in northwestern Iowa. The main threats will once again be brief heavy downpours, hail to the size of a quarter, and to a lesser extend damaging wind gusts of 60+ mph. An additional 0.1 to 0.25" are possible with the highest again being east of the SD/MN/IA border. Eventually rain will change over to freezing rain/drizzle or sleet to a wintry mix before becoming all snow overnight.

The timing of the change over remains uncertain due to timing differences in the cold front passage in the short term guidance.
About half of the guidance has the front over central South Dakota around to shortly after midnight tonight. While the other half indicate a slower passage around or shortly after 6 am Friday. This 6 hour difference continues as the front progresses through eastern South Dakota and into western Minnesota and Iowa. This leaves uncertainty in ice and snow totals very high at this time. One thing that does appear more certain at this time is an area of prolonged freezing rain and drizzle for portions of east central South Dakota, southwestern Minnesota, and northwestern Iowa. Here there may be between 0.1 to 0.2 inches of ice accumulations before switching over to snow. For this reason, a Winter Weather Advisory has been issued from 3 pm Friday through 9 am Saturday morning. Snow moves clear of the area by late morning Saturday.

Saturday afternoon skies will clear and we will warm into the 40s to 50s. Sunday a high pressure skirts to our south, turning winds southwesterly and increasing WAA. Highs will warm into the 60s and winds will be diurnally breezy gusting 20-25 mph. Flow aloft becomes slightly more zonal for Monday. A short wave passes along the US/CAN border which will give a weak push of CAA that cools highs to the 50s for areas north of I-90, 60s to the south both Monday and Tuesday. Wednesday brings another chance for rain with cooler highs in the 40s. Then things dry out and warm again into the 50s and 60s for the remainder of the week.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/
Issued at 525 PM CST Thu Mar 5 2026

VFR conditions begin the overnight hours, however we'll quickly see the development of mid clouds associated with warm advection arrive from the south. Scattered showers and even a rumble of thunder will be possible along and east of I-29 (though moreso over NW Iowa) into mid-morning Friday.

Also, concerned that the arrival of lower stratus and general saturation of the lowest levels will lead to fog development after 3am. Would not be surprised at all if dense fog forms along I-29 and into portions of SW Minnesota and NW Iowa.

The passage of front from the west northwest will bring a wind shift, but may also lead to periods of drizzle into the afternoon. That drizzle may switch to rain showers at times in the afternoon as both ceilings and visibility remain low. Have kept a more pessimistic outlook regarding vis/cigs.

Eventually cold air will filter southeast transitioning showers to a wintry mix and then snow later in the evening.

FSD WATCHES/WARNINGS/ADVISORIES
SD...Winter Weather Advisory from 3 PM Friday to 9 AM CST Saturday for SDZ040-055-056-061-062-067.
MN...Winter Weather Advisory from 6 PM Friday to 9 AM CST Saturday for MNZ071-072-080-081-089-090-097-098.
IA...Winter Weather Advisory from 6 PM Friday to 9 AM CST Saturday for IAZ001>003-012>014.
NE...None.