Winter Storm Tracker: Cold, Snow and Rain to Sweep US and Canada

A fierce winter storm is expected to unleash a combination of heavy snowfall, freezing rain and bone-chilling winds across the Central and Eastern United States in the coming days. A blast of Arctic air will also plunge much of the country into bitter and, in some cases, dangerous cold, forecasters say.

The frightful conditions are already afflicting parts of the West, with airports canceling and delaying hundreds of flights ahead of the holiday weekend. Across the nation’s middle, warnings from the authorities were growing increasingly ominous. Front line workers are also becoming apprehensive of what some forecasters have described as a “once-in-a-generation storm.”

Over 100 daily cold temperature records could be tied or broken over the next few days, according to forecast data from the National Weather Service.

Brian Hurley, a senior forecaster for the service’s Weather Prediction Center in College Park, Md., said that the gravest concerns at this time were for blizzard conditions, as well as the precipitous drop in temperature and wind chill expected across several states.

“It’s going to be very cold during the day,” Mr. Hurley said.

Here’s a breakdown of how each region could be affected:

The West and the Plains

The “record-breaking” cold air mass has already enveloped some parts of the region between the Rocky Mountains and the Sierra Nevada, as well as the Central Plains, and will chill the Southern Plains by late Thursday, according to the National Weather Service. Temperatures across the region have already plummeted to minus 10 to minus 20 degrees, with bone-chilling wind gusts of up to 60 miles per hour creating wind chills as low as minus 40 degrees, forecasters say.

In Cheyenne, Wyo., the cold air moved swiftly, dropping a record 40 degrees in just 30 minutes — from 43 degrees to three on Wednesday afternoon. The temperatures have continued plummeting, reaching as low as minus 13, with wind chills feeling more like minus 40 early Thursday morning.

In some parts of this area, the wind chill could reach as low as minus 70 degrees, according to the Weather Service. Without adequate precautions, these conditions can cause frostbite in under five minutes, said the service, “with hypothermia and death also possible from prolonged exposure to the cold.” There is also concern for the welfare of livestock, especially if there is a widespread loss of power.

Brief bursts of moderate to heavy snow lasting an hour or two are likely to occur immediately behind the Arctic front. These so-called snow squalls, when combined with strong wind gusts, can cause whiteouts, leading to “extremely hazardous” travel conditions, the Weather Service said.

The Pacific Northwest

While the majority of the coastal West, including California, will be spared the bitter cold and punishing weather, some parts of Oregon and Washington State could experience “significant freezing rain,” the Weather Service said, with the potential for ice accumulation to create dangerous travel conditions and scattered power interruptions. Wind chill warnings have also been issued for parts of Washington State.

Texas and the Southeastern United States

On Thursday evening, temperatures in Texas and the Gulf Coast will likely be in the single digits and teens, about 20 to 30 degrees below normal, forecasters say. The temperatures could drop rapidly, and in some parts of the region, could remain below freezing for two to three days, according to the Weather Service.

Wind chill watches and advisories are in effect for much of the Southeastern U.S. In parts of Texas, wind chills — a measure of what the combination of temperature and wind feels like to human skin — could reach a dangerous minus 15 degrees, the Weather Service said. It advised residents to avoid extended time outdoors, and, if they have to brave the cold, to cover exposed skin.

“We’re actually looking at windshield down into the single digits, even some areas are expected to be down in the negative values,” Sam Marlowe, a forecaster with the Atlanta National Weather Service office, said. “Most people here are not used to that.”

The Midwest

Subzero to single-digit temperatures are expected throughout much of the Midwest, according to forecasters. Vast portions of the region are also under winter storm and blizzard warnings. Such conditions can greatly impair visibility and travel.

In Illinois, the Weather Service warned of bitter wind chills of minus 15 to minus 35 degrees from Thursday night into Saturday, and snowfall of up to four inches on Thursday. Blizzard conditions, the service said, would be possible from Thursday through Friday night.

The heaviest snowfall, according to forecasters, is likely to occur between Wednesday night and Friday over the Great Lakes, where the total depth could exceed a foot. Wind gusts of more than 50 m.p.h. will create near-zero visibility, leading to what the Weather Service described as “dangerous, to at times impossible, land and air travel.” There is also concern for tree damage and widespread power failures.

But the snow doesn’t have to be heavy to become dangerous. Snow combined with 50 m.p.h. winds across the Plains, through the Midwest and into the Great Lakes will create blizzard conditions with any snow falling or on the ground already.

The potential for this to be a “bomb cyclone,” which is meteorologist jargon for a storm system that drops 24 millibars (a measure of air pressure) or greater in 24 hours or less, will lead to extreme winds across the region.

Cities across the region, including Cleveland and Peoria, Ill., are preparing to open warming centers to allow residents to seek shelter during the storm.

Northeastern United States

By late Thursday or Friday, the storm system will have reached the Mid-Atlantic, bringing with it moderate to heavy rainfall of one to three inches, forecasters say. Strong southerly winds, combined with the new moon-tide cycle, could also bring coastal flooding from northern New Jersey to northeast Massachusetts, the Weather Service said.

In parts of Vermont and Maine, heavy rain over a fresh snowpack could lead to flooding, according to the service. Parts of the central Appalachians may also receive light freezing rain and locally heavy snowfall on Thursday morning.

Buffalo and the surrounding area are under a blizzard warning, with the worst hitting them Friday night into Saturday. Meteorologists warned local residents that this is not a normal lake effect event with a narrow band of heavy snow. Instead, the moderate to heavy snow will be more widespread.

“True blizzard conditions are rare in Western N.Y.,” forecasters in the Buffalo, N.Y. weather office warned, “and it’s unusual to even consider blizzard headlines this far in advance of a storm. However, the magnitude of this storm justifies this consideration.”

On Friday, as the Arctic cold front races eastward, temperatures will drop suddenly from the mid to upper 50s down to the 20s or the teens, the service said. This rapid plunge in temperature can flash freeze wet surfaces like roads and pavements, creating hazardous conditions.

A flash freeze occurs when moisture on surfaces like roadways doesn’t have time to evaporate before temperatures quickly dive below freezing, creating black ice conditions.

Canada

While a bout of extreme cold grips western Canada, eastern provinces, including Ontario, should expect a mix of snow and rain on Thursday, followed by plummeting temperatures, heavy bursts of snow and gusty winds over 60 m.p.h., meteorologists say.

“With that quick transition from above zero to below zero, we’re looking at potentially iced roads in some places as well, so extremely difficult travel conditions across southern Ontario,” said Steven Flisfeder, a federal warning preparedness meteorologist.

At Toronto’s Pearson International Airport, which is Canada’s busiest transportation hub, travelers are bracing for cancellations and delays. Heavy snowfall near Vancouver International Airport has already led to the cancellation or delay of hundreds of flights.

The intensity of the snowfall is expected to subside by Saturday evening in Ontario and Quebec, though flurries and snow squalls remain possible in the region surrounding the Great Lakes, forecasters said.

Vjosa Isai and Judson Jones contributed reporting.