December is looking chillier in Philly. Is there a chance of snow before Christmas?

As if it were honoring the calendar, the atmosphere over Philly on Thursday’s opening day of the meteorological winter has an appropriately seasonal bite with morning wind chills in the 20s a daytime high about 30 degrees lower than it was on Nov. 1.

And while the chill isn’t expected to persist into the weekend, forecasters say that it is likely to return late next week, and that it might even snow around here during the next round of cold.

In a change from its earlier outlook favoring a warmer-than-normal December in the region, the government’s Climate Prediction Center on Wednesday said the temperature forecast now is a coin flip.

It also favors below-normal readings through Dec. 13, with patterns over the North Atlantic and Arctic often favorable to snow in the Northeast.

In short, the early indications are arguing against a repeat of the ultra-mild and snow-less December 2021, when Philly’s temperatures were a balmy 6.7 degrees above normal.

» READ MORE: Early outlooks saw a mild winter in Philly

“Some of the tele-connections are matching up enough to bring a few cold shots and potential snow to the Northeast in the first half of the winter season,” said Paul Pastelok, the veteran seasonal forecaster with AccuWeather Inc.

While temperatures are due to make a run at 60 degrees Saturday, after likely failing to get out of the 40s Thursday and Friday, the first week of December isn’t going to resemble the first week of November.

While last month won’t rank among the warmest Novembers in Philly records dating to 1874, several temperature records were toasted.

Readings hit 70 degrees or better on the first seven days of the month, an unprecedented streak. That same week saw a record-high minimum for November, 67, and a record high, 79. In all, temperatures reached 70 or higher on 10 days, a November record, besting the nine of 1975.

As a result of a significant midmonth cooldown, November’s average temperature finished at 50.9, only 3.5 degrees above normal.

The Climate Center’s winter forecast still favors above-normal temperatures around Philadelphia and in much of the nation for the Dec. 1-to-Feb. 28 meteorological winter. Its most recent outlook had a 27.3% chance of below-normal temperatures, up from 22% in the previous forecast, but that’s a subtle difference.

While the center’s discussion posted Wednesday cited upper-air patterns over the North Atlantic and Arctic that often favor cold and storminess, AccuWeather’s Pastelok said the behavior of the polar vortex won’t warm the hearts of ski interests.

The vortex has shown signs of strengthening. When that happens, winds tend to confine the coldest air to the Arctic regions.

» READ MORE: Philly winters aren't what you think

The wild card, of course, is atmospheric chaos. Nothing happens in a vacuum in the 10-mile-deep ocean of air sloshing above the planet’s irregular surface. Meteorologists’ descriptions evoke an environment whose behavior can resemble that of a drunk carrying a full bucket of water. One thing can go wrong in a forecast, and everything else comes tumbling after.

Snow or its absence, for example, would make a huge difference in the fate of temperatures. If none is on the ground in Philly, Pastelok said, “the warm-ups in the second of December can be quite noticeable. ... Some days may wind up 15 to 20 degrees above normal.“

It’s almost always safe to take the under if you’re betting on Christmas snow. Based on data assembled by the National Centers for Environmental Information, the odds against measurable snow in Philly on Dec. 25 are 12-1.

It hasn’t happened around here since 2009.

Pastelok is not bullish on snow’s chances of staging an upset this year. He suspects that the late-December pattern won’t favor cold in the East.

He said that high pressure develops in the upper atmosphere close to the Northwest coast, and that could drive cold air toward the East: Winds circulate clockwise around high centers, so areas to the east experience northerly winds. However, he suspects the high will park farther off the coast, chilling the Plains.

» READ MORE: White Christmas usually is just a dream

The Old Farmer’s Almanac says the Philly region definitely has a shot at snow for Christmas.

It also predicted below-normal temperatures for November.