The Most Bizarre and Notable Things From the December Windstorm and Severe Outbreak

"I can say with some confidence that this event - the heat and tornadoes - is among the most, if not the most, anomalous weather events ever on record for the upper Midwest," weather historian Christopher Burt said.

So here are the many strange and record-breaking aspects of this event that made it so notable for this time of year.

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First December Tornado in the Land of 10,000 Lakes

Prior to this outbreak, there hadn't been a December tornado documented in Minnesota dating to 1950.

There had only been one severe thunderstorm warning issued in Minnesota in December prior to this storm, according to tornado researcher Harold Brooks at the National Severe Storms Laboratory.

Dec. 15, 2021, shattered that.

Numerous severe thunderstorm and tornado warnings were issued as the squall line roared across southeast Minnesota.

Damage in Hartland, Minnesota, was from an EF2 tornado, just one of 11 others in the state.

Rare December Derecho

A squall line of severe thunderstorms raced about 660 miles in 10 hours from Kansas and Nebraska to northern Wisconsin with destructive winds and embedded tornadoes.

This easily met the criterion for a derecho: a widespread damaging windstorm produced from thunderstorms.

Derechos are very rare in December; they're typically a late spring to summer phenomenon. Only about 1% of derechos in the U.S. have happened in December, according to NOAA's Storm Prediction Center.

This serial derecho was driven by an intense cold front slicing into unusually warm and humid air for mid-December. (More on that warmth later.)

The SPC also noted Wednesday had the most 75+ mph thunderstorm wind gusts in any 24-hour period since at least 2004. As the NWS-La Crosse, Wisconsin, pointed out, "Damage would have been much, much worse had trees been leafed out."

First December "Moderate Risk" Outlook For Upper Midwest

NOAA's Storm Prediction Center issued a severe weather outlook Wednesday morning that was shocking.

The outlook called for a "moderate" risk for severe thunderstorms, the second-highest of five levels of severe risk in daily forecasts.

That alone would grab the attention of meteorologists.

But this level 4 of 5 risk was in the upper Midwest. It was the first time SPC had issued such a high-level severe forecast in Iowa, Minnesota and Wisconsin in December.

It was also a bizarre location for such a dire severe outlook in any winter month.

Upper Michigan's Midnight Thunderstorms

While the squall line of thunderstorms finally weakened upon reaching Upper Michigan, the lightning show it put on was quite a sight for December.

One of our Twitter followers tagged us with a screengrab of a video he took from Houghton, Michigan, capturing the moment a lightning flash lit up the night sky.

Yes, there were thunderstorms in Upper Michigan's Keweenaw Peninsula around midnight, just nine days before Christmas.

The Houghton County Memorial Airport recorded a temperature of 51 degrees just after midnight, a record high for the date. An average mid-December day in northern Upper Michigan should only see the daytime high rise to around 27 degrees.

You could even see some bare patches of grass in the screengrab above. Houghton has an average mid-December snowpack of 14 inches.

It Started As a Snow Haboob

Before this storm shifted into high gear, it created a surreal sight Wednesday morning along the Colorado Front Range.

As the cold front plowed east and descended the Rockies, a line of snow swept through the Denver-Boulder-Ft. Collins urban corridor.

The visuals resembled a classic Desert Southwest dust storm, or haboob, except it was snow caught up in the blast of winds.

Since it happened at sunrise, it took on an orange tinge. There was even a double rainbow.

This storm was also called Winter Storm Bankston by The Weather Channel as it produced heavy snow in the West. But it didn't produce heavy snow in the Plains or Midwest, yet another weird aspect to this December storm.

It Then Became a Dust Storm

Once the front swept east, its high winds whipped up dust from the drought-suffering High Plains into a major dust storm.

Visibilities were quickly reduced to near zero as the front blasted parts of eastern Colorado, southwest Nebraska and western Kansas.

Interstate 70 was closed in both directions from Hays, Kansas, to the Colorado border due to "brownout conditions".

Here was the sight in Lamar, Colorado, Wednesday morning.

100+ MPH Gusts

Wind gusts from 40 to 60 mph are usually at least capable of triggering power outages and knocking some tree branches down.

What we saw on Wednesday far surpassed that.

Several locations clocked gusts of 100 mph or more, including Lamar, Colorado (107 mph); Taos Ski Area, New Mexico (103 mph); the U.S. Air Force Academy north of Colorado Springs (100 mph) and Russell, Kansas (100 mph).

Des Moines, Iowa, had its highest non-thunderstorm wind gust (74 mph) in 51 years, and Dodge City, Kansas, had a wind gust stronger than any thunderstorm's in that town's history.

At one time, NWS high wind warnings covered 36 million people, or roughly 1 in 10 Americans and about 20% of the area of the Lower 48 states.

Speaking of 100 mph, one NWS tornado warning in Iowa and Nebraska estimated the severe thunderstorm had a forward speed of 100 mph, the likes of which rarely seen in an NWS warning.

Plains Wildfires Spread Smoke to the Great Lakes

High winds, very low humidity and dry ground made an ideal recipe for rapidly-spreading wildfires.

For the first time in December, NOAA's Storm Prediction Center issued an "extremely critical fire weather outlook" from the northern Texas Panhandle to northern Kansas.

Fast-moving wildfires threatened Skellytown, Texas; Guymon, Oklahoma; and areas just to the north of Russell, Kansas.

The storm's strong winds lofted smoke hundreds of miles into the Great Lakes Wednesday night.

By early Thursday morning, a faint whiff of the High Plains wildfire smoke was in the air as far away as Chicago, La Crosse, Wisconsin, and Michigan, among other locations.

It wasn't just smoke, either. One central Illinois meteorologist found a coating of High Plains dust on his car in central Illinois. Dust even made it into an NWS rain gauge in Duluth, Minnesota.

All-Time December Record Highs Smashed

Parts of the Plains and Midwest had a case of spring fever on this mid-December day.

Both Iowa (78 degrees at Oskaloosa) and Wisconsin (72 degrees at Boscobel) set new all-time December statewide record highs.

Des Moines, Iowa, reached 70 degrees in December for the first time in its 143-year history. It did so before noon. The high of 74 degrees is typical of May 21 or September 24 instead of the week before Christmas.

The Weather Channel meteorologist Mike Seidel was in Des Moines and captured the view below just after lunch.

Madison, Wisconsin (68 degrees); Rochester, Minnesota (64 degrees); and Rockford, Illinois (69 degrees) were among other cities with December records

Snowstorm's Footprint Erased

On Dec. 10-11, parts of Minnesota and Wisconsin were hammered by up to 21 inches of snow from Winter Storm Atticus.

You could still see piles of snow in the lawn of one storm-damaged home east of Eau Claire, Wisconsin, late Wednesday night.

Five days later, the warmer winds, fog and soaking rain from the derecho erased the snowpack in eastern Minnesota and western Wisconsin.

In this and many other ways, this resembled a storm in spring or early fall, rather than a core winter month. It's also one most in the Plains and upper Midwest won't soon forget.

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