By daybreak Friday wind chills will fall into the low 20s around here. Come Saturday morning, Philadelphia will be about 10 degrees colder than Anchorage, Alaska.

Pennsylvania, New Jersey, Delaware, and about 35 other states in the eastern two-thirds of the nation are about to become blue states. Blue as in cold.

An extensive and particularly deep area of lower pressure — a trough — that favors cold air and precipitation will prevail in the upper atmosphere over eastern North America well into next week, according to the government’s Climate Prediction Center.

Beyond the cold temperatures, computer models have been hinting at the potential for snow threat, centered on Tuesday. But as usual, they are having a hard time agreeing on what they’re seeing.

On Wednesday, for example, the American model envisioned a major snowstorm; the European, a nuisance event after some rain, said Bob Larsen, senior meteorologist at AccuWeather Inc. On Thursday morning, the European was holding its ground, the American shoveled all the measurable snow to the north.

Expect snow to play peek-a-boo with the models at least through the weekend, and keep in mind that that this time of year, precipitation type is almost always an issue and tougher for models to resolve.

Besides, the front and attendant storm expected to bring rain to the region late Thursday into Thursday night could affect what happens next week.

The government's 6-10 forecast has a mightily cold, blue cast.
The government's 6-10 forecast has a mightily cold, blue cast.

The cold, though, appears to be an ice-hard reality. After a period of rain late Thursday afternoon into Thursday night, Friday will feel January-like with temperatures struggling to get out of the 30s. Saturday will be a few degrees warmer, but not much.

The chill will ease Sunday and Monday, but temperatures still will remain below normals, and second shot of cold air will accompany next week’s storm threat.

Larsen said that regardless of whether it’s snow or bust on Tuesday, the models agree in predicting “one of the more prolonged cold snaps I’ve seen this time of year for awhile.”

As typically happens this time of year, while cold air is still seeking an identity in the Northern Hemisphere, conditions in the East are the mirror opposite of the West.

Relative to normal, Alaska will be downright balmy. The government’s forecast low for Anchorage for Saturday, 35 degrees, would be higher than Philadelphia’s expected low of 26. Of course, Anchorage’s temperature would be 17 degrees above normal; Philadelphia’s, 15 below.

Around here, temperatures in the lower 40s on Friday will be a good 15 degrees below normal.

Overall, it’s beginning to look a lot like last year. The high in Philadelphia on Nov. 2, 2018, was 72. A significant cooldown started the next week, and on Nov. 13, the region had what turned out to be its biggest snowfall of the season — 3.6 inches at Philadelphia International Airport.

This year, the high reached 75 on Halloween, hours before that power line-ripping squall line hit, and an imminent, significant cooldown is a certainty.

As for snow, around here usually it isn’t a certainty until the shoveling is over, but the models might be on to something.

“You got the setup you need for November,” said Tony Gigi, a former National Weather Service meteorologist who helps run the phillywx.com discussion board. Plenty of cold air would be overhead and-or nearby, and Atlantic sea-surface temperatures off the mid-Atlantic coast are several degrees above normal. Those would be storm-inducing contrasts.

A wild card would be how the storm forecast to affect the region Thursday night into Friday roughs up the atmosphere, said Paul Walker, a senior meteorologist at AccuWeather Inc.

“We don’t know how the atmosphere is going to look,” he said. Nothing happens in a vacuum up there, and what goes before affects what comes after.

Whatever does or doesn’t happen, a wintry outbreak this early isn’t necessarily a harbinger, as was evident last year, and might not even be a harbinger for the rest of November. Only about 14 more inches of snow fell for the season; the long-term average is just over 22.

In its updated November outlook, posted on Halloween, the climate center said the odds favored below-normal temperatures in the Northeast. But after a cold first half, it saw a “monstrous transition in the pattern.”

Would that suggest a warm Thanksgiving?

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