“Brief bursts of heavy snow, strong wind gusts, and rapidly falling temperatures will likely lead to sudden whiteouts, flash freezing, and icy roads,” the National Weather Service wrote. “Even in areas unaffected by snow, dangerous cold is expected.”

Nearly 70 million people are under winter storm watches or warnings in the Midwest, Great Lakes and Appalachians, and blizzard warnings have recently been hoisted in Minnesota.

Snow and strong winds could affect major airport hubs, including Chicago’s O’Hare International and the Detroit Metropolitan Wayne County airports. The combination of snow and winds gusting over 40 mph will result in blowing and drifting snow that reduces visibility to near zero at times, particularly in a zone from western Kansas and Nebraska northward to Minnesota extending eastward through western New York.

“Whiteout conditions are expected … with travel becoming very difficult or impossible,” wrote the National Weather Service in Minneapolis. “This event could be life-threatening if you are stranded.”

Cities that could deal with blizzard conditions between Thursday and Friday — at least for a short interval — include Kansas City, Mo., St. Louis, Des Moines, Minneapolis, Milwaukee, Chicago, Indianapolis, Detroit and Buffalo.

Here are the forecasts for 10 cities in the path of Christmas week blizzard

In some places near the Great Lakes, including Buffalo, wind gusts could reach 50 to 65 mph, causing significant tree damage and power outages amid dangerously low temperatures.

Locations from the Rockies eastward that avoid snowfall will not escape near record-cold temperatures running some 40 degrees or more below normal. Wind chill watches, advisories and warnings affect about 90 million people, extending from the Canadian border to Texas and as far east as Tennessee, with subfreezing temperatures likely to plunge down to the Gulf of Mexico. In some places, temperatures will be the lowest in decades during the month of December.

Over the north central United States, actual air temperatures of minus-20 to minus-40 are expected, and wind chills could flirt with minus-60. The National Weather Service in Bismarck, N.D., is calling the cold “life-threatening.”

“The dangerously cold wind chills could cause frostbite on exposed skin in as little as 5 minutes,” it wrote.

That cold will make it to the East Coast on Friday, abruptly arriving as a flash freeze that could send temperatures plummeting 25 degrees or more in just a few hours. Coming after a morning of heavy rainfall and perhaps a short burst of snow, the flash freeze may turn some roadways into treacherous sheets of ice, potentially leading to extremely hazardous travel on major thoroughfares like Interstates 95, 84 and 81.

In the Northeast, the same storm system — which will intensify so rapidly it will qualify as a weather “bomb” — will push water against the coastline, causing coastal flooding.

An upper-air disturbance, characterized by a pocket of high altitude cold air, low pressure and spin, will dive out of British Columbia and Alberta over the central Plains on Wednesday and Thursday. It will explosively strengthen a surface low pressure zone pushing across the Plains, transforming it into a powerhouse storm system that will sweep up the Ohio Valley. By Friday night, it’ll be cruising into Quebec and Ontario en route to the Hudson Bay.

The storm will rapidly intensify as a bomb cyclone, a designation given to the most intense mid-latitude weather systems. Its pressure will drop from 1003 millibars Thursday night near the Indiana-Ohio border to 968 millibars Friday night — which is the approximate pressure of a Category 2 or 3 hurricane — over southern Quebec. Mid-latitude storms whose pressure falls 24 millibars in 24 hours are considered meteorological bombs — this storm’s pressure is projected to fall 35 millibars in that time. The lower the pressure, the stronger the storm.

Since low pressure systems spin counterclockwise, the system will draw in a tongue of mild air on its eastern side. That will keep most of the Mid-Atlantic and Northeast predominantly rain. The exception will be in the Appalachians, specifically the Alleghenies of western Maryland, western Virginia and eastern West Virginia, where cold air entrenched in the mountains will be difficult to scour out.

The National Weather Service is warning of 4 to 7 inches of snow east of the Allegheny front, in addition to a quarter inch of ice from freezing rain. This will occur the first half of Thursday. That’s just round one of the storm before the flash freeze arrives Friday — not just for mountains, but also areas toward the coastal plain — including Washington and Baltimore.

D.C.-area forecast: Cold and calm today, then wet tomorrow before an Arctic onslaught

A major Plains and Great Lakes blizzard

Farther west, however, the Plains, Upper Midwest and even parts of the Mid-South, perhaps as far south as Nashville, will see snow — and for some, a lot of it. The jackpot, which could feature a foot or more, looks to fall in the Upper Peninsula of Michigan, with a secondary maximum downwind of Lakes Erie and Ontario.

Even in areas that only see a few inches of snow, travel is expected to still be extremely dangerous because of high winds that will limit visibility.

St. Louis, Kansas City, Omaha and the Twin Cities are under winter storm warnings, with a general 2 to 6 inches of snow likely to fall — lesser south, more north. West of Minneapolis, a blizzard warning is in effect; the combination of 40-50 mph winds and moderate to heavy snow could make for whiteout conditions during the height of the storm Thursday night into Friday, while the wind and cold could lead to wind chills below minus-30.

In Chicago, Detroit and Indianapolis, a winter storm watch is in effect. That’s where confidence is lesser on just how much snow will fall. In the Windy City, totals will likely range between 3 and 6 inches, but will walk a steep gradient; accumulation will quickly climb as one drifts toward Michigan, with a foot or more likely falling in parts of the mitten.

In the storm’s wake, cold air blowing out of the west-northwest across Lakes Erie and Ontario could brew some lake-effect snows, although it’s not a classic wind direction for extreme accumulations, since it doesn’t blow lengthwise down the lakes. Instead, a foot or so is likely over the weekend, though meteorologists are still fine-tuning the details.

“Travel for the holiday weekend, including Friday, could be very difficult to impossible at times” through Monday, wrote the Weather Service in Buffalo.

Here’s what to know about the lake-effect snow

Behind the storm, a plume of Siberian air will be shunted southward into the United States, lasting about 72 hours and affecting nearly everyone east of the Rockies. It will first creep across the Canadian border into early Wednesday, blasting south as a cold front that will drop temperatures 40 degrees or more in just under six hours.

The biting chill will blast into Denver on Wednesday night, dropping temperatures from 40 degrees to zero in just a matter of hours. By Thursday morning, it will be near minus-10 with wind chills around minus-30.

“Life Threatening Cold Arrives Late Wednesday,” tweeted the Weather Service office serving Denver. “We promise that’s not an exaggeration. This is likely to be the coldest day in 32 years in Denver so many people have not experienced a cold snap like this.”

Over the Dakotas, temperatures could dip to near minus-30 on Friday night. In Bismarck, they’ve been below zero since Sunday, and will stay that way until Christmas. Wind chills of minus-40 are likely. Breaking down in a vehicle without an emergency kit on hand could very quickly become deadly.

That cold will plunge southward, arriving in St. Louis on Thursday. Highs will peak in the mid-30s with snow, quickly falling to around minus-3 at night. Friday won’t climb above the single digits.

In Oklahoma City, Thursday won’t make it above 11 or 12 degrees. In the Texas Panhandle, temperatures could drop from highs near 50 on Wednesday to the teens by midnight. Locally, such fronts are known as “blue northers.”

The cold will blast all the way to the Gulf Coast by Thursday afternoon, transforming the ocean into a seemingly smoking lagoon. That will be due to “Arctic sea smoke,” or a unique type of fog which forms when frigid air blows over warmer waters.

How to prepare your home before the blizzard and arctic air strikes

Flash freeze in the eastern U.S.

The cold will reach the East Coast on Friday, but will do so abruptly. That will spell a danger for those driving on area interstates, particularly between Washington, D.C., and Hartford, Conn.

Temperatures on Friday morning will be in the 40s to near 50, with rain likely to fall as moisture swirls into the parent low pressure system to the northwest. As the cold front comes through around noontime, readings will plummet into the 20s, with temperature drops of 25 degrees or more likely in a three-hour window. At the same time, a very brief period of snow is possible.

Crews won’t be able to pretreat the roadways due to the rain, and any lingering moisture and puddles could quickly turn to ice. That could leave roadways highly treacherous. There’s some chance strong winds help dry roads before they can ice over, but pockets of dangerous travel are a risk.