Polar vortex: Snow first, minus 20s to minus 30s this weekend

Twin Cities rides the edge of snow Thursday; 100-plus subzero hours ahead

Advisories and snowfall forecasts
Advisories and snowfall forecasts
Twin Cities National Weather Service

Minnesota’s other winter weather shoe is about to land with a thud.

Thursday brings snow and wind to eastern Minnesota, Wisconsin and Iowa. This weekend brings the coldest air of the winter season.

Here’s a breakdown on the major winter pattern change ahead.

Winter weather advisories

Winter weather advisories run south and east of a Duluth-Twin Cities-Luverne line Thursday. Little or no snow will accumulate in western Minnesota. The Twin Cities rides the edge of the 1 to 3-inch zone. Heavier snow will fall in southeast Minnesota and Wisconsin.

Advisories and snowfall forecasts
Advisories and snowfall forecasts
Twin Cities National Weather Service

Including the cities of Center City, Minneapolis, Blaine, St Paul, Stillwater, Chanhassen, Chaska, Victoria, Shakopee, Hastings, Le Sueur, and Osceola 249 PM CST Wed Feb 3 2021

...WINTER WEATHER ADVISORY IN EFFECT FROM 3 AM TO 3 PM CST THURSDAY...

* WHAT...Mixed precipitation expected, with mainly snow after 6 AM. Some freezing drizzle and patchy blowing snow is also possible. Total snow accumulations of up to two inches and ice accumulations of a light glaze.

* WHERE...Portions of northwest Wisconsin and east central and south central Minnesota.

* WHEN...From 3 AM to 3 PM CST Thursday.

* IMPACTS...Plan on slippery road conditions. Patchy blowing snow could educe visibility. The hazardous conditions could impact the morning commute.

Gusty winds

Winds will gust over 30 mph Thursday. That will cause blowing snow and poor visibility. Driving conditions will be difficult Thursday. Blizzard warnings are up for northern Iowa along Interstate 35.

Forecast peak winds Thursday
Forecast peak winds Thursday
Twin Cities National Weather Service

Here’s a timeline for the storm from the Twin Cities National Weather Service office.

Forecast storm timing
Forecast storm timing
Twin Cities National Weather Service

Polar vortex outbreak

I’ve been wondering when and if the Mother Lode of bitterly cold air will be coming south into Minnesota this winter. We have our answer.

Watch how the arctic floodgates open and a lobe of the polar vortex drives bitterly cold air into Minnesota this weekend on this upper air (500-millibar) loop.

NOAA GFS upper air forecast
NOAA GFS upper air forecast anomalies
NOAA via tropical tidbits

Forecast models gauge the coldest temperatures this weekend between about minus 15 and minus 30 across Minnesota. But they also often underestimate the magnitude of extreme events.

My best assessment is that temperatures will range between minus 15 and minus 20 in the Twin Cities Sunday and Monday mornings. Minus 30s seem likely up north. Some of the colder nooks and crannies could approach minus 40.

NOAA’s GFS model is among the colder members this weekend.

NOAA GFS temperature forecast for 6 am Sunday, February 7
NOAA GFS temperature forecast for 6 a.m. Sunday.
NOAA via pivotal weather

100-plus subzero hours?

Temperatures may stay below zero in the Twin Cities and much of Minnesota from Friday night until at least Tuesday afternoon. That could mean at least 100 hours below zero for many locations.

Forecast hours below zero
Forecast hours below zero
Twin Cities National Weather Service

Stay safe and stay warm Minnesota.

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