Chilly and energetic pattern

An impressive early winter Arctic air mass moved into the Northland this afternoon, with 850mb temperatures dropping to between -21°C and -26°C, and 500mb temperatures falling to -32°C to -38°C. Meanwhile, 500mb heights have lowered to between 514 and 528 meters.

For reference, 850mb corresponds to about 5,000 feet in the atmosphere, while 500mb is roughly 18,000 feet.

Note: If Duluth sees temperatures drop below -10 degrees tomorrow morning, December 4th, 2025, it would be just the fifth time since 1874 that it’s been that cold. The most recent was in 1991 with a low of -16, and the other years were 1886, 1972, and 1950.

The 18z GFS model indicates 500mb temperatures dropping to around -51°C near the core of the upper low over southern James Bay, Canada, early this evening.

Those temperatures at 500mb are about -2 to -3 sigma below average for early December, which is pretty impressive!

At 5 PM today, temperatures in International Falls had already dropped to -1, while the rest of the Northland is experiencing temperatures ranging from 0 to around 10 degrees.

Record Lows for December 4th

International Falls, MN: -28 set in 1908
Brainerd, MN: -23 set in 1991
Hibbing, MN: -17 set in 1991
Duluth, MN: -16 set in 1991
Ashland, WI: -9 set in 1972

Tonight’s lows will range from about -5 to -20 degrees.

As we shift from cold air advection to a warm advection pattern on Thursday, some snow is likely to develop across parts of northeast Minnesota and northwest Wisconsin, particularly in the afternoon and evening.

A clipper low approaching from the northwest will also bring in some lift into this Arctic airmass, which should help in generating some snowfall.

There are more chances for snow in northeast Minnesota and northwest Wisconsin on Friday and next week as an active weather pattern develops, potentially including a stronger storm from the Rockies next weekend (~December 12-14), but that’s a long way down the road.

RAP model simulated radar forecast valid 7 AM to 11 PM Thursday.

Snow that falls should be pretty fluffy tomorrow afternoon and evening, with accumulations of about 1 to 3 inches possible across northern Minnesota, and a trace to an inch farther south, including in Duluth and Superior.

Note: The Arrowhead region near Grand Marais could see 2 to 4 inches of snow, with a chance of lake-enhanced snowas winds shift to the south on Thursday.