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Winter’s return: Extremely cold air set to spill into central U.S.

There will be several opportunities for snow, sleet or freezing rain over central and possibly eastern United States

Lows Saturday night as predicted by the National Weather Service. (Pivotal Weather) (WeatherBell FTWP)
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Parts of the central United States have been feeling more like spring than winter as of late, with repeated severe weather outbreaks and above-normal temperatures. Winter is about to make a swift return, however, with frigid air and multiple opportunities for snow and icy precipitation.

We built a fake metropolis to show how extreme cold could wreck cities

The jury is still out on just how far southeast the chilly Canadian air will go, and there’s an outside chance the East Coast will miss out on the core of the cold. But wherever the periphery of the cold air ends up, a corridor of snow, sleet and freezing rain is likely as storm systems straddle the clashing air masses.

In parts of the northern Rockies and Upper Midwest, the cold will be the most intense since the record-breaking blast just before Christmas. The air won’t be quite as frigid this time, but temperatures could dip as low as minus-25 Monday morning with wind chills near minus-40 in parts of Wyoming and northern Minnesota.

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The pattern change comes as a glimmer of hope to snow-starved winter enthusiasts in the Mid-Atlantic and Northeast, where measurable snow has yet to fall in New York, Philadelphia, Baltimore or D.C. Some weather models indicate the potential for wintry weather toward the middle of next week — but for those on the precipice of a record-long snowless streak, it’s too early for celebration.

The pattern change

The evolving pattern is far from a classic “cold air outbreak” one; in fact, the coldest air, perhaps close to 40 degrees below-average, will remain over the Columbia River Basin, northern Rockies, Dakotas and Upper Midwest. That said, the cold is far from meteorologically meager — the Plains and Ohio Valley will still get into the ice box swell.

More significant than the actual magnitude of the cold will be the shuffling of storm tracks and weather systems to follow, which could expose more of the United States to snow.

An upper-level low pressure system is hovering over the Hudson Bay right now, its tail end parked over Saskatchewan and Manitoba. Winds are spinning counterclockwise around it, and that tugs frigid air from the north down across Alberta and British Columbia. But milder air is wafting northward on its eastern side, meaning winter’s worst has been staved off over the Great Lakes, the Midwest and the East.

By the early to middle of next week, however, that low is going to shift east and consolidate as high pressure builds in across the West. That will create a persistent northwesterly flow for southern Canada, the northern Plains, the Great Lakes, the Mid-Atlantic and New England.

That will entrench bone-chilling air in the Rockies, with “leftover” cold pushing east. It’s not a single, textbook Arctic blast but multiple pulses of cold Canadian air that will plunge southeastward.

Temperature trends

Cold air will begin to gather over southern Canada on Friday night, combining into a concentrated mass of low temperatures that will head south into Sunday. It will be heralded by a strong cold front that will shift south and east over the Central Plains.

Consider the situation in Grand Island, Neb. Highs approached 40 degrees on Friday, but were set to fall for the next 36 to 48 hours. Saturday’s high is expected to peak around 23 degrees, and by late Saturday night into Sunday morning, Grand Island could dip below zero.

In Aberdeen, S.D., highs near freezing on Friday will likely dip to the lower teens for highs over the weekend; Sunday morning could dip to minus-7 degrees.

Denver is expecting a gradual stairstep down into bitter cold territory. The Mile-High City was set for highs in the upper 40s to around 50 on Friday. Saturday should be closer to 30, Sunday will peak around 16, and Monday may not make it out of the single digits. Sunday and Monday nights could show lows around minus-3.

Minneapolis, meanwhile, is forecast to see highs in the single digits on Saturday, Sunday and Monday; nights will flirt with minus-10.

Farther south, St. Louis should get the cold in a two-part installment. After reaching the lower 50s on Saturday, the city should see highs in the mid-30s Sunday and the 20s on Monday and Tuesday.

Some moderation is likely mid to late next week.

Where to watch for wintry weather

At least two systems are set to impact the Rockies and the central part of the country; the first will likely bring snow, and the second could feature more of a messy wintry mix.

Weekend system

A fast-moving system over southern Alberta — known as a clipper — is expected to bring snow to western Montana, northern Idaho and the northern half of Wyoming from Friday night into the first half of Saturday. Accumulations should be light in the lowlands, with between 4 and 8 inches of a plowable snow possible in the higher elevations. Wind chills of minus-25 degrees or lower should invade behind the snow.

Farther east, that narrow strip of moderate snow will likely spread along the Nebraska-South Dakota border early Saturday and across the northern half of Iowa north of Interstate 80. The snow will ease in intensity on approach to Chicago as the clipper merges with another weather system.

Winter weather advisories blanket the system’s path, although a few winter storm warnings are up where forecasters believe extra snow may fall.

Middle of next week

By the middle of next week, given uncertainties in the overall pattern, making a forecast more specific than “there could be a storm” is impossible. The overarching pattern would favor one or more waves of low pressure moving through the southern Plains and perhaps across the Mid-South and Tennessee Valleys.

Depending on how far south the cold air bleeds, there could be a shallow lip of subfreezing air hugging the ground. If this happens, it would be a classic recipe for overrunning — or warm, moist air from the south riding up and over the low-topped layer of cold. That would result in liquid rain falling and freezing on contact with the surface, raising concerns about freezing rain and ice. Some snow would probably fall just to the north of any ice. It’s too soon to say where the dividing lines between rain, ice and snow will set up.