North Shore Chinook: Temperatures pushing 50 degrees in Grand Marais on Dec. 9

It’s becoming a December to remember in Minnesota. For unusual reasons.

An unseasonably mild air mass is wafting over Minnesota again today. Temperatures are soaring through the 40s and pushing the 50-degree mark in parts of Minnesota today.

One spot soaking up the unusual December warmth is Grand Marais and other North Shore communities. Temperatures at the Bay at Grand Marais spiked to near 50 degrees around midday. Temperatures in the 40s are common along the North Shore.

North Shore Chinook

One weather phenomenon that North Shore residents occasionally experience is downslope winds. These wind patterns are driven by various factors. The Duluth NWS Office elaborates on the downslope wind event that occurred on November 30, 2020.

These so-called “dry adiabatic” air masses warm about 5 degrees per thousand feet of descent. So the roughly 1,700-foot drop between Eagle Mountain (2,306 feet ASL) and Lake Superior (610 feet ASL) delivers between 5 and 10 degrees of downslope warming. Temperatures spiked in Grand Marais Wednesday as the gusty winds raced downhill.

It’s the same effect as the downslope Chinook winds in the Rockies.

That’s why locations along the North Shore like Grand Marais can feel these rapid temperature spikes during gusty downslope events.

Throw in the lack of snow cover and bright sunshine and you’ve got the recipe for an unusually warm December day along the North Shore.

Mild all over

Temperatures also surged through the 40s and reached the 50-degree mark in the Twin Cities by midday Wednesday.

It’s another day where highs temperature forecast guidance is falling short of actual observed temperatures in much of Minnesota. here’s what NOAA’s digital forecast data predicted for high temperatures Wednesday.

We cool down slightly Thursday and back into the 30s this weekend. But temperatures will still run several degrees above average as we move into mid-December.