textproduct: Duluth

KEY MESSAGES

- Areas of light freezing drizzle mainly along and west of the US-53 corridor may create slippery stretches on area roads through this morning. Sidewalks may also become slippery. Freezing drizzle will taper off late this morning into early afternoon.

- Another round of light precipitation is forecast this afternoon and tonight. Precip is expected to start as rain before changing to snow. There may be a period of light freezing rain over portions of northwest Wisconsin tonight. Ice accumulations will be less than a tenth of an inch. Snow totals will be less than half an inch.

- Warming conditions begin today with daytime highs rising above freezing into the 40s and 50s through the rest of the week. - A better organized clipper will move through the region over the weekend. Mixed precipitation is forecast.

DISCUSSION

Issued at 417 AM CDT Wed Mar 18 2026

As of 3 AM...

The Northland is under a southwest to northeast oriented baroclinic zone (an area in the atmosphere featuring a "notable" horizontal temperature gradient) at the surface and aloft located to the northeast of a quasi-stationary front over the eastern Dakotas. Westerly winds aloft were providing a broad area of isentropic ascent over much of Minnesota. An upper-level trough extended from around 925 mb to 700 mb and was responsible for most of the light snow overnight. The trough axis was over the Minnesota Arrowhead to northeast Illinois at 08Z and will continue to propagate east. The low stratus over the region in the wake of the snow was largely the result of the isentropic ascent mentioned earlier. Thermal profiles reveal a relatively deep cloud layer which appears to top out around 700 mb over northwest Wisconsin tapering down to around 850 mb near Brainerd and International Falls. The dry air aloft will continue to erode the clouds from top down. As that occurs warm air advection aloft and decreasing cloud top heights will support a chance from snow to freezing drizzle. Between 1 and 3 AM ASOS stations at Brainerd, Duluth, and Park Rapids reported ice accumulation accompanied by cloud bases below 1000ft and visibility between 3 and 6 miles. GOES-East night microphysics RGB reveals mainly liquid water cloud tops west of a line from Pine City to Bigfork to Baudette. Areas east of the line are a little fuzzier with a possible mix of liquid droplets and ice crystals. Observations across the area varied between "mist" and light snow.

Early this morning...

The latest RAP forecasts indicate the isentropic ascent will persist through this morning with stratus lingering. We expanded the coverage of light and very light freezing drizzle with this forecast package based on trends, model forecasts, and observations. While the ASOS ice accumulation sensors help confirm the existence of freezing drizzle when other data support the occurrence, it's this forecaster's subjective opinion the actual values reported are unreliable. Even so, with persistent light to very light freezing drizzle, there is a potential for slippery roads for the morning commute. We will monitor trends and road conditions. A short-term Winter Weather Advisory for freezing drizzle may become necessary if indications of ice accumulation persist over portions of central and north-central Minnesota.

Rest of today and tonight...

Temperatures will warm above freezing today into this evening as warm air advection continues. The afore mentioned baroclinic zone will remain over the region while a upper-level jet streak and area of 500 mb vorticity propagate southeastward into Minnesota by tonight. Freezing drizzle will gradually taper off from southwest to northeast this morning. It may linger into the early afternoon over the Arrowhead. The approaching speed max aloft will provide another boost to isentropic ascent and a diffuse area of frontogenesis. Most deterministic and high-res model guidance features an area of precipitation over north- central Minnesota which will advance into northwest Wisconsin this evening. It's not easy to piece together the various dynamic contributions to that precipitation chance. Subtle height falls, confluent flow in the 850 to 700 mb layer, a diffuse area of frontogenesis, and a transient zone of omega will all play a part. Temperatures will start out above freezing leading to a period of rain as precipitation begins. Later this evening and overnight in northwest Wisconsin there may be a period of freezing rain with accumulation between 5 hundredths and a tenth of an inch. The main question will be how quickly road temperatures cool after sunset. As of this forecast the potential for 5 hundredths of an inch of freezing rain over northwest Wisconsin is less than 20%. Rain will eventually change to snow before ending over northeast Minnesota with less than half an inch of snow expected.

Thursday through Friday night...

The broad upper-level pattern willStrong southerly winds will weaken and veer westerly this morning. Small Craft Advisory remains in effect for Grand Marais to Grand Portage. Waves of 3 to 6 feet early today will subside to 1 to 3 feet by this afternoon. The next period of hazardous conditions will develop this weekend as a more organized low pressure system moves through the region.

For the open water discussion, refer to the NWS Marquette Area Forecast Discussion at weather.gov/mqt. remain unchanged for the remainder of the work week. A large blocking high over the southwest US will remain in place with a ridge over the western US. Northwest flow will persist over the northern Plains and the Canadian Prairies into the western Great Lakes. Weak and persistent warm air advection will continue allowing temperatures to warm into the upper 30s to middle 40s Thursday and low 40s to middle 50s on Friday. Another shortwave trough will propagate through the northwest flow Thursday night and early Friday morning. Model guidance reveals an area of mixed precipitation over Ontario to the central Great Lakes during that time. Portions of the Arrowhead have a chance of a rain/snow mix as that system passes by.

With the warm air advection and temperatures climbing well above freezing during the day, there is a potential for widespread dense fog to develop as early as Thursday evening. Once the fog develops, it will be hard to shake until the pattern changes. Dense Fog Advisories will likely be needed later this week. Another complicating factor on temperatures will be the presence of the fog. The warm air advection alone doesn't appear strong enough to raise temperatures 10 degrees from Thursday into Friday. If the fog develops and persists, temperatures may be 10 degrees cooler than forecast for Friday.

Saturday into next week...

A pattern shift is forecast for the weekend into next week. The blocking high over the southwest US will weaken and an upper- level trough is forecast to propagate through the northern US and southern Canada. Details vary depending on which model we consider. Overall there is a chance for widespread precipitation possibly as early as Saturday morning. The warmer temperatures will remain in place at the start which will give a mix of rain and snow. A few inches of snow to shovelable or plowable amounts are possible. If precipitation begins Saturday and changes to snow Saturday night, look for higher totals. If precipitation doesn't arrive until Sunday morning, lower totals are likely. The fast-moving clipper will be short-lived with drier and warmer conditions returning for Monday and Tuesday. A few shortwave troughs may pass over the Northland Monday night through Wednesday. Each one would bring a chance of precipitation, likely a mix of rain and snow.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 638 AM CDT Wed Mar 18 2026

Low IFR to MVFR stratus persists early this morning across the region. Patchy freezing drizzle has been observed underneath this stratus and will continue on and off until temperatures rise above freezing by the afternoon. There are indications of improvement to MVFR and even some VFR in north-central Minnesota around midday. A second round of wintry precipitation arrives late this afternoon into tonight, bringing conditions back down to IFR and potentially LIFR. KHYR will have the best chance of seeing freezing rain/drizzle tonight leading to a glaze of ice, with a rain/snow mix for the other TAF locations.

MARINE /FOR NEARSHORE WATERS OF WESTERN LAKE SUPERIOR/

Issued at 1040 AM CDT Wed Mar 18 2026

Winds veer westerly this morning. Small Craft Advisory remains in effect for Grand Marais to Grand Portage. Waves will subside to 1 to 3 feet by this afternoon. The next period of hazardous conditions will develop this weekend as a more organized low pressure system moves through the region.

For the open water discussion, refer to the NWS Marquette Area Forecast Discussion at weather.gov/mqt.

DLH WATCHES/WARNINGS/ADVISORIES

MN...None. WI...None. MARINE...Small Craft Advisory until 4 PM CDT this afternoon for LSZ140.