Dangerous cold returns to Wisconsin: –15° to –30° wind chills possible

MILWAUKEE - Wisconsin is heading into one of its coldest stretches of the season as a surge of Arctic air arrives late this week. 

The FOX6 Weather Experts expect temperatures to dip into the single digits Wednesday night and Thursday morning and then plunge well below that late week, with wind chills of –15 to –30 degrees possible Friday night into Saturday night.

Arctic cold

What we know:

Those values are cold enough to trigger wind chill advisories or warnings, and the National Weather Service has let us know they anticipate that advisories or warnings are possible as the pattern sharpens.

Unlike a typical cold snap, this one is driven by a series of reinforcing waves that keep feeding colder and colder air into the state. Highs this weekend may not get above the single digits, while overnight lows dip below zero for at least a couple of nights. For many parts of southern Wisconsin, this will be the first truly dangerous cold of the season.

Wind chills are likely to be in the double-digits below zero by Saturday morning and stay there through Saturday afternoon and into Sunday morning. This can be dangerous, especially for those planning to spend time outside. 

What triggers an extreme cold weather advisory, watch, or warning?

Dig deeper:

It is a common question this time of year: "How cold does it have to be for the NWS to issue cold weather alerts?"

In Wisconsin, advisories or warnings are typically issued when cold weather and brisk wind chills fall into ranges that could lead to frostbite in 30 minutes or less. The upcoming patter points directly at those thresholds or lower, with multiple hours of "dangerously cold" wind chills possible both Friday night and Saturday night. The old verbiage was to use wind chill advisory, watch, or warning, but the NWS goal was to create more uniform headlines for cold weather strikes. Wisconsin will likely be added to either a cold weather advisory or extreme cold warning by the weekend. 

Are you ready?

What you can do:

• Limit time outdoors before frostbite becomes a risk
• Prepare for much colder-than-normal buildings, vehicles and classrooms
• Give pets shorter outdoor breaks to keep them safe
• Watch for slick spots as extremely cold air refreezes roads and sidewalks.

Even for those used to Wisconsin winters, –30 wind chills demand respect.

The Arctic Front: Why the bottom drops out

Big picture view:

While it will be cold Wednesday night and Thursday morning, the truly dramatic cold arrives behind a strong arctic front sweeping across the Great Lakes on Friday. That front will pull down a deep pool of polar air that has spent days over northern Canada, growing colder with time.

A few key ingredients driving the plunge:

1. Reinforcing shortwaves

Several additional disturbances roll through with each wave, allowing another push of cold air to spill south, preventing any warm-up in between.

2. Clear skies and light winds at night

Behind the front, the sky clears and winds weaken. The result is perfect conditions for temperatures to drop below zero.

3. Fresh snow cover

Snow from earlier in the week will act like a refrigerator, helping overnight lows dip even further.

4. Strong pressure gradient

A significant difference between the high and low pressure centers over our region drives a much stronger flow across the region and means wind chills drop sharply.

How long will the deep freeze last?

What's next:

The cold holds firm through the weekend, but there’s relief on the horizon. By Monday, winds turn southerly and temperatures begin rebounding toward seasonal norms. By Tuesday, highs should return to something closer to December's normal for the climate period.

Until then, Wisconsin is buckling up for the kind of cold that makes your eyelashes freeze. Bundle up and looks for ways to stay warm.  Check our list of warming centers on this site.

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