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Mildest winter on record for much of Minnesota

Lowest winter severity index so far; another thaw on the way

Accumulated Winter Season Severity Index
Accumulated Winter Season Severity Index.
Midwest Regional Climate Center

Welcome to the mildest winter on record so far for much of Minnesota.

The Midwest Regional Climate Center’s Accumulated Winter Season Severity Index (AWSSI) for Minnesota shows that the Twin Cities, Duluth, International Falls, Austin, and Winnebago are all on pace for the mildest winter on record.

The Twin Cities AWSSI value of 185 through Jan. 15 is the lowest on record.

Accumulated Winter Season Severity Index Twin Cities
Accumulated Winter Season Severity Index for the Twin Cities.
Midwest Regional Climate Center

Another thaw on the way

We’ll say goodbye to subzero weather by next week.

Another pattern change in the upper winds will blow milder Pacific air masses into Minnesota and the Upper Midwest for the next one to two weeks starting Sunday.

In fact, the pattern change looks so extensive and persistent that it could cover most of the United States and persist until at least the first days of February.

The National Oceanic and Atmospheric Administration’s Global Forecast System model shows the upper airflow across the U.S. changing starting this weekend and lasting through Feb. 1.

Look how persistent the warm colors (above-normal upper-air heights) are in our region in the last 10 days of January:

Upper air forecast map for
Upper-air forecast map between this Sunday and Feb.1.
NOAA, via Tropical Tidbits

Now check out NOAA’s Global Forecast System model temperature output (below) starting Sunday morning. See how we replace arctic air with milder temperatures and a string of days with highs in the 30s across southern Minnesota? Note the expansion and temperatures around 40 degrees on the last frame on Jan. 30.

NOAA GFS temperature output
Global Forecast System temperature output between Jan. 20 and Feb. 1
NOAA, via Tropical Tidbits

Recall that forecast models show higher skill with large-scale temperature trends in weeks one and two. So forecasters don’t take the specific numbers for gospel, but there’s good reliability on warmer temperature trends heading into late January.

El Niño fingerprint

Our supersized El Niño winter appears to be ready to revert to the balmy mean.

A strong flat west-to-east flow pattern aloft is called zonal flow by meteorologists. In winter it produces much warmer than normal temperatures across most of the northern United States.

El Niño impacts
Typical El Niño winter impacts
NOAA

NOAA’s six to 10-day temperature outlook strongly favors warmer-than-normal temperatures next week.

NOAA 6 to 10-day temperature outlook
6 to 10-day temperature outlook
NOAA

The eight to 14-day outlook also favors warmer-than-normal temperatures through the end of January.

NOAA 8 to 14-day temperature outlook
8 to 14-day temperature outlook
NOAA

It looks likely we’ll melt most of what little snow cover we have in southern Minnesota next week.

Shortest winter?

The warmest December on record has already assured us of a shorter-than-normal winter in Minnesota.

It will be interesting to see what February brings. I suspect we’ll have at least one more subzero outbreak in February. But overall this super El Niño is playing out as advertised.

If we escape February and early March without severe cold with little or no snow cover, it’s quite possible we’ll have an early spring in much of Minnesota.

If we get an early spring this year, this will be the shortest winter I have lived through in Minnesota.

Stay tuned.