textproduct: Duluth

KEY MESSAGES

- Widely isolated patches of dense fog are expected this morning and should dissipate by mid-morning.

- Clouds and possible fog development early this morning may limit heating today. Temperatures will climb above freezing. Areas where skies are partly cloudy or clear during peak heating will reach the upper 40s to low 50s.

- A weak clipper will move across the Canadian Prairies and northern Minnesota tonight. Expect a mix of rain and freezing rain starting late this morning and ending tonight over north- central Minnesota into the Arrowhead. Ice potential is greatest in Cook County.

- Widespread fog is expected tonight due to snow melt and southerly winds. Fog will be locally dense. - A better organized clipper will move through the region over the weekend. Mixed precipitation is forecast.

DISCUSSION

Issued at 422 AM CDT Thu Mar 19 2026

A stripe of low stratus stretched from near GPZ to Upper Michigan at 3 AM and will continue to slowly progress southward this morning. There is a 10% chance of very light freezing drizzle with that cloud deck. The other concern early this morning is the potential development of fog. Low-level moisture received a small boost from snowmelt and southerly warm air advection yesterday afternoon. Clear to mainly clear skies over much of northeast Minnesota along with relatively light winds will allow for radiational cooling. The main question is whether the cooling will be rapid enough to generate dense fog or if direct deposition of ice onto surfaces will limit fog formation. INL visibility was at 1/4 mile for a few minutes in the last hour and is back to 5 miles now. Reduced visibility is expected to become more widespread before sunrise, but widespread dense fog appears unlikely.

A clipper located over southern Alberta early this morning will propagate east-southeastward across the Canadian Prairies and into northeast Minnesota by early Friday morning. The regional radar mosaic reveals a band of light precipitation over southern Manitoba which appears showery in nature. High-res models are beginning to capture that precipitation. The 00Z Hi-Res FV3 and 07Z RAP seem to have the best handle at the moment. Those models bring light precipitation into the International Falls vicinity late this morning and into the eastern Arrowhead through early afternoon. Temperatures are expected to warm above freezing resulting in rain as the main weather type. There is about a 10% chance of freezing rain even with air temperatures above freezing as precip begins.

Elevated instability and Lifted Indices near zero this afternoon into this evening over the Borderlands suggests a potential for a few rumbles of thunder. Warm air aloft persists as the second wing of precipitation advances into the Arrowhead this evening into the overnight. Surface temperatures will drop below freezing which raises the potential for freezing rain mainly over Cook County. The chance of freezing rain is about 40% and the probability of 5 hundredths of an inch of icing is around 25%.

With another warm day on tap today and strengthening southerly warm air advection ahead of the clipper, the stage will be set for the development of widespread fog tonight, some may be locally dense. If the fog develops, it will be difficult to shake until the weekend. The forecast highs for Friday will hinge on whether fog and low stratus develop tonight. If we see clearing, highs will reach the upper 40s to low 50s. Otherwise we can expect upper 30s to middle 40s. I took the warmer path for now.

Another period of precipitation is forecast Saturday and Sunday. The persistent baroclinic zone over the Northland (an area in the atmosphere featuring a "notable" horizontal temperature gradient) will feed into a weak area of low pressure traversing the Northland Saturday. That system will be similar to today's clipper. Precipitation chances will be greatest north of the low track. As of this morning that area includes most of northeast Minnesota and northwest Wisconsin. With the system riding right along the baroclinic zone and 0 *C isotherms bisecting the Northland, a mix of rain, snow, and possibly freezing rain is forecast. Slight wobbles in the track of the low and the thermal gradient aloft will influence precip types. As of this morning snow amounts are a dusting up to an inch. The likelihood of precip being all snow is low, around 10-30% depending on location with the greatest odds of all snow in Cook County. For areas where there is a mix...rain, snow, sleet, and freezing rain are all possibilities.

Another shortwave trough will move into the region by Saturday night. Another round of wintry mixed precipitation is favored. The second round of precipitation is shaping up a bit stronger with another dusting up to an inch of snow possible and higher totals along the North Shore. Total snow between both systems will range from a dusting up to an inch or two for most locations and up to 3 inches in the high terrain of the North Shore. Precipitation should taper off Sunday morning although the GFS solution keeps light snow in the picture through Sunday.

Early next week will see warm temperatures during the day cooling below freezing at night. There are a few additional chances of precipitation Monday night and then Tuesday night into Wednesday. Both of those would be clipper-type systems with relatively light precipitation.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1233 PM CDT Thu Mar 19 2026

VFR conditions continue, but low clouds are moving east off Lake Superior and are expected to affect DLH and later HIB with MVFR ceilings. LLWS will also affect HIB, HYR, and BRD between 00-09Z this evening/tonight. Fog is also expected to occur tonight, particularly across the Arrowhead and northwest Wisconsin. IFR to LIFR conditions are possible. HIB is more uncertain in the models, but still gave it a TEMPO due to how often we see fog form there under favorable conditions.

MARINE /FOR NEARSHORE WATERS OF WESTERN LAKE SUPERIOR/

Issued at 422 AM CDT Thu Mar 19 2026

Winds will be from the east to southeast today and will veer southwesterly tonight as a low pressure system propagates southeastward across northwest Ontario. Sustained winds of 5 to 10 knots are forecast and will increase to 8 to 15 knots for the waters of the South Shore tonight. Hazardous conditions are not expected at this time. Fog is forecast to develop onshore tonight and may advect onto the water. If that occurs, expect visibility less than 1 mile near the shore. The next period of hazardous conditions is forecast for the weekend when a stronger low pressure system is forecast to pass over the region. Strong east and northeasterly winds will develop Saturday afternoon and become hazardous during the evening hours. There is a 20-30% chance of low-end gales along the North Shore and the southwest arm Saturday night and early Sunday morning. Waves will build to 3 to 9 feet with the highest values in the waters of the southwest arm and over the Outer Apostle Islands. Winds are forecast to weaken Sunday afternoon and night. Small Craft Advisories will likely be needed.

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...None.