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 around, but temperatures could drop to minus 25 Monday morning with chills near minus 40 in parts of Wyoming and northern Minnesota.
A winter storm in Christmas week and arctic blast through the ages, as you can see in the numbers
The pattern change comes as a glimmer of hope for snow-hungry winter enthusiasts in the Mid-Atlantic and Northeast, where measurable snow has yet to fall in New York, Philadelphia, Baltimore or DC. halfway through next week – but for those on the brink of a record-long snowless streak, it’s too early to celebrate.
The evolving pattern is far from a classic “cold air breakout”; in fact, the coldest air, perhaps nearly 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 be in the ice swell.
More important than the actual extent of the cold will be the shaking of storm tracks and weather systems to track, which could expose more of the United States to snow.
An upper-level low-pressure system is currently hovering over Hudson Bay, with the end parked over Saskatchewan and Manitoba. The wind rotates counterclockwise, pulling icy air from the north into Alberta and British Columbia. But milder air is blowing north on the eastern side, meaning the worst of winter has been averted over the Great Lakes, Midwest and East.
By early next week, however, that low will shift eastward and consolidate as high pressure builds in the west. That will create a sustained northwesterly flow for southern Canada, the northern plains, the Great Lakes, the Mid-Atlantic and New England.
That will entrench the frigid air in the Rockies, with “leftover” cold to the east. It’s not a single Arctic blast, but multiple pulses of cold Canadian air that will plummet to the southeast.
Cold air will begin to gather over southern Canada Friday night, combining into a concentrated mass of low temperatures that will move south on Sunday. It will be heralded by a strong cold front moving south and east across the Central Plains.
Consider the situation in Grand Island, Neb. Highs approached 40 degrees Friday, but would drop over the next 36 to 48 hours. Saturday’s high is expected to be around 23 degrees, and Grand Island could dip below zero by late Saturday night into Sunday morning.
In Aberdeen, SD, Friday highs around freezing will likely drop to lower teens for highs on weekends; Sunday morning can drop to minus -7 degrees.
Denver expects a gradual descent into bitterly cold territory. The Mile-High City was set to highs in the upper 40s to about 50s on Friday. Saturday should be closer to 30, Sunday peaks around 16 and Monday may not break the single digits. Sunday and Monday nights can see lows around minus 3.
Meanwhile, Minneapolis is predicted to see single-digit highs on Saturday, Sunday and Monday; nights will flirt with minus 10.
Farther south, St. Louis should get the cold in a two-part. After reaching the lower 50s on Saturday, the city should see highs in the mid-30s on Sunday and the 20s on Monday and Tuesday.
Some moderation is likely mid to late next week.
What to watch out for in winter weather
At least two systems will affect the Rockies and the central part of the country; the first is likely to bring snow, and the second may contain more of a messy wintry mix.
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 Friday evening through the first half of Saturday. Piles should be light in the lowlands, with between 4 and 8 inches of plowable snow possible in the higher elevations. Wind sock temperatures of -25 degrees or lower should penetrate behind the snow.
Farther east, that narrow band of moderate snow is likely to spread along the Nebraska-South Dakota border and across the northern half of Iowa north of Interstate 80 early Saturday. system.
Winter weather advisories are covering the system’s path, although there are a few winter storm warnings where forecasters believe additional snow could fall.
Midway through next week, given the uncertainties in the overall pattern, it’s impossible to make a forecast more specific than “a storm could be coming.” The overarching pattern would favor one or more low-pressure waves moving through the southern plains and perhaps the Mid-South and Tennessee Valleys.
Depending on how far south the cold air flows, there may be a shallow lip of below-freezing air hugging the ground. If this happens, it would be a classic recipe for overrun — or warm, moist air from the south drifting up and over the low layer of cold. That would result in liquid rain falling and freezing upon contact with the surface, raising concerns about sleet and ice. Some snow would likely fall just north of any ice. It is still too early to say where the dividing lines between rain, ice and snow will be.