A Powerful Storm to hit the upper Midwest with a variety of impacts likely tonight and Thursday

This will be a storm to remember because of the variety of weather it will bring to the Northland, including a highly unusual risk for severe weather and tornadoes in parts of Minnesota and Wisconsin in mid-December!

POTENTIAL IMPACTS TONIGHT AND THURSDAY

  • Damaging winds with tree and power line damage
  • Widespread power outages
  • Rain (heavy at times)
  • Scattered thunderstorms
  • Isolated severe thunderstorms
  • Flash freeze
  • Snow
  • Near blizzard conditions
  • Rapidly falling temperatures

WEATHER ALERTS

There are a variety of weather alerts in effect across the Northland for tonight and Thursday.

-High Wind Warning including the cities of Grand Marais, Silver Bay, Two Harbors, Duluth, Hill City, Aitkin, McGregor, Brainerd, Pine River, Walker, Cass Lake, Hinckley, Pine City, Superior, Solon Springs, Bayfield, Washburn, Port Wing, Ashland, Hurley, Gile, Danbury, Grantsburg, Siren, Minong, Shell Lake, Spooner, Hayward and Winter.

-Winter Storm Warning including the cities of Walker, Grand Rapids, Pine River, International Falls, Bigfork and Ely.

-Winter Weather Advisory including the cities of Isabella, Hibbing, Two Harbors, Silver Bay, Grand Marais, Brainerd, Hill City, Aitkin, Duluth, Pine City and Hinckley.

-Wind Advisory including the cities of Isabella, Hibbing, Grand Rapids, International Falls, Ely and Bigfork.

We’re also seeing widespread dense fog in the Northland this afternoon, and this should linger into this evening before the fog and visibility improves later this evening and overnight.

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Very strong to potentially damaging wind gusts are expected in northeast Minnesota and northwest Wisconsin Thursday morning. These high winds will spread SW-NE across the area beginning after Midnight tonight. Wind gusts of 40 to 50 mph are likely, with a potential for wind gusts as high as 60 mph in parts of the Northland.

For Duluth: Strong winds develop ~2 AM to 4 AM Thursday and continue throughout the day, although the strongest gusts are expected prior to Noon on Thursday. Wind gusts of 40 to nearly 60 mph are possible in the Twin Ports Thursday morning.

RAPIDLY FALLING TEMPERATURES THURSDAY MORNING

Very mild temperatures will remain over the Northland this evening with temps in the 40s and 50s with near 60-degree temperatures possible in parts of northwest Wisconsin, but much colder air will work in from the west and south after Midnight tonight with temperatures falling into the teens and 20s area-wide by midmorning on Thursday.

For Duluth: Temperatures of 45 to around 50 degrees at Midnight tonight falling to 27 to 32 degrees around 6 AM Thursday and to the mid-teens to low 20s by Noon Thursday.

The potential does exist for a flash freeze to occur in some parts of the Northland Thursday morning.

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TIMING OF PRECIPITATION AND THE CHANGEOVER FROM RAIN TO SNOW

As low-pressure approaches from the southwest, the amount of forcing will increase markedly tonight with widespread rain expected to spread SW-NE across the Northland.

Colder air on the backside of the northeastward moving low pressure system will cause the rain to turn to snow after Midnight tonight, and this changeover from rain to snow will spread from west to east across the Northland early Thursday morning.

Snow is expected to taper off from west to east Thursday afternoon.

Note heavy snowfall rates of 1 to 2 inches per hour are possible early Thursday morning across parts of north-central Minnesota.

For Duluth
Rain develops this evening (after 7 PM)
A few thunderstorms possible before Midnight
Rain changes to snow Thursday morning (~4 AM to 6 AM)
Snow tapers off Thursday afternoon

With how quick this system moves through, I think it will be difficult to get more than 3-5″ of snow in parts of north-central Minnesota, but it won’t take much snow to create very hazardous road conditions when you combine the snow with the strong winds, falling temperatures and rain that will fall prior to the changeover to snow.

The same can be said for anywhere in northeast Minnesota and northwest Wisconsin, so even though snow amounts might not be much more than an inch outside of northern Minnesota, the combination of this new snow falling on top of the rain that falls tonight, mixed in with the strong winds and falling temperatures, all leads to potentially hazardous if not dangerous driving conditions Thursday morning.

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All of the maps below are from 4 PM Wednesday, December 15, 2021

A strong area of low pressure over east-central Nebraska continuing to lift NE.

Strong warm air advection (red colors) ahead of the low with strong cold air advection (blue colors) west/southwest of the low.

Very powerful winds in the mid-levels of the atmosphere today with a sting jet blasting NE out of Kansas with 500mb wind speeds >120 knots.

Extremely humid air mass for mid-December with precipitable water of an inch or more (green colors) over a large portion of the Midwest, this moisture will surge north into Minnesota and Wisconsin this evening.

Dew points in the 50s as far north as Minneapolis, MN and Siren, WI late this afternoon with dew points around 60 a little further south. Incredible for mid-December!

Tim

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