Flash freeze to shock Midwest after another dose of snow

Screen shot: AccuWeather

Dec. 7, 2019 (AccuWeather) — Midwesterners may have a tough time deciphering exactly which season we’re in this weekend and next week — and forecasters stress that rapid weather changes may be dizzying.

Meteorologists are tracking a storm system and an air mass that will be major players in the weather whiplash expected across the region. A swath of snow and a rapid freeze-up associated with a blast of Arctic air have the potential to hinder travel and shut down schools over parts of the Midwest early next week.

A storm will track from the central Plains on Monday to the eastern Great Lakes on Tuesday.

At this time, AccuWeather meteorologists anticipate a swath of moderate to heavy snow to sweep from parts of the Dakotas to central and southern Minnesota, northern Wisconsin and northern Michigan.

Given the storm’s anticipated track, cities such as Minneapolis; Eau Claire and Wausau, Wis.; and Marquette and Sault Ste. Marie, Mich. are likely to get enough snow to shovel and plow.

However, light snow is likely to fall over a more extensive area.

While the light snow itself would not typically cause a huge problem, it is the small amount of snow that falls, partially melts and causes roads and sidewalks to turn into a sheet of ice as frigid air pours in.

Cities that could receive enough snow to lightly coat roads include Omaha, Neb.; Des Moines, Iowa; Milwaukee; Chicago; South Bend, Ind.; and Detroit and Lansing, Mich.

Rainfall with the storm over the Central states will generally be unremarkable, but problems are in store after the rain ends.

“In some areas, winds may not have a chance to dry off roads and sidewalks before below-freezing air arrives,” Brian Wimer, AccuWeather winter weather expert, said.

The colder air will sweep in like a rocket to the southeast over the Central states with the main thrust from the northern and central Plains to the Great Lakes and the Ohio and Tennessee valleys.

Don’t be fooled by a taste of spring

What will work against a widespread rapid freeze-up from the Ohio and middle Mississippi valleys on south will be the surge in warmth ahead of the storm.

On Sunday and Monday, temperatures will surge into the upper 40s to near 50 in the lower Great Lakes and the 50s and 60s farther south ahead of and during most of the rain.

This warmup will allow many roads and sidewalks to retain some warmth and allow the moisture to dry off before the freeze-up.

However, if the rain lingers for a few hours as cold air arrives, the chance of a quick freeze-up will increase substantially in places such as St. Louis, Cincinnati, Indianapolis and Louisville, Ky., on Tuesday.

There’s even a remote chance of a flash freeze as far south as Nashville, Tenn.

In terms of the magnitude of the Arctic air on the way, this outbreak will represent the lowest temperatures of the season so far by an average of 10 degrees to 25 degrees Fahrenheit.

For example, the lowest temperatures in Minneapolis, Chicago, and St. Louis occurred back on Nov. 12, when the temperature dipped to 5, 7 and 11 degrees, respectively. The same outbreak of Arctic air set low temperature marks for the season so far on Nov. 13 in Detroit, Cincinnati and Nashville of 7, 10 and 11 degrees, respectively.

The combination of temperature, wind and other atmospheric conditions will result in AccuWeather RealFeel Temperatures plunging to dangerous levels and well below zero from the northern Plains to the upper Great Lakes by Tuesday.

Conditions cold enough for frostbite will dip into the middle Mississippi Valley and lower Great Lakes during Tuesday as well.

By Wednesday, actual high temperatures are forecast to range from the subzero and single digits in northern Minnesota to the upper 30s in the lower Ohio Valley.

Even people along the central Gulf Coast will feel some chill with highs in the upper 50s to near 60 on Wednesday.

Feet of lake-effect snow may follow storm

As the coldest outbreak of the season so far spreads across the Great Lakes, an equally significant lake-effect event will be unleashed.

“We expect this to be the most substantial lake-effect snow event of the season so far throughout the Great Lakes region,” AccuWeather broadcast meteorologist Laura Velasquez said.

Whether a few inches to a few feet of snow falls or not will depend on how long the bands of snow linger over a particular area.

“Steering winds will tend to cause the snow bands to shift around over time, but some areas are still likely to get clobbered by a foot or more of snow,” Velasquez said.

“These places include the Upper Peninsula of Michigan, the western part of the Lower Peninsula of Michigan, northwestern Indiana, western and central New York state, northwestern Pennsylvania and the northeastern corner of Ohio,” Velasquez added.


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