» UPDATE: Follow along here for the latest on what to expect with Thursday’s snow

A significant winter storm is likely Thursday, forecasters are saying with growing confidence, with several inches of snow possible in and around Philadelphia, along with perhaps several hours of sleet.

The National Weather Service’s winter storm watch for the entire region from 4 a.m. Thursday through 1 p.m. Friday remains in effect, and in all likelihood will become a winter storm warning Wednesday afternoon, even if an inch or so gets trimmed off the expected snowfall forecast it posted in the morning.

While it would be wise to draw any snow maps in pencil, based on what has and hasn’t happened the last three weeks, meteorologists are nearly certain that something substantial is coming, and that it would be related to the historic and disruptive winter outbreak in Texas.

If it appears as though a piece of the Arctic has broken off and sunk all the way to the Mexican border, that’s close to what has happened, said Lara Pagano, a meteorologist with the government’s Weather Prediction Center.

Close to 4.5 million customers were without power in the Lone Star State as of Tuesday afternoon — and still 2.5 million Wednesday morning — the result of winter storms and the cosmic cold that Pagano said rivals Arctic outbreaks of 1899 and 1905.

“There are hundreds of records being broken,” she said.

Some of that air has migrated to the Gulf of Mexico, where temperatures well offshore are in the 70s, and the contrasts are the stuff that storms are made of. “You have quite a tight temperature gradient,” she said. Another storm is due to take shape Wednesday in the Gulf region, with upper-air currents bearing it northeastward toward the Ohio Valley, where it is expected to spawn a coastal nor’easter.

» READ MORE: Scene through the lens: Winter across the region

Precipitation will start as snow around here Thursday morning, with total accumulations depending on when the snow would yield to sleet and/or freezing rain. It is unlikely that areas west of the Delaware River will see any plain rain before it all ends sometime Thursday night or Friday morning, said Tom Kines, senior meteorologist with AccuWeather Inc.

After the sun’s first serious appearance in eight days on Tuesday, temperatures made it to 50, routing the icicles and giving the remnants of the snowpack an unleavened look. But a front came through in the afternoon, and temperatures Wednesday might not get past freezing after quite a chilly morning. It should be cold enough for snow Thursday.

» READ MORE: Why Philly storm forecasts have been conflicting and constantly changing this winter

Cold, but not Texas cold. “It is very shocking,” said Tevin Wooten, a Weather Channel meteorologist who has been reporting from Dallas. He said that the streets are empty, most people are not venturing out of heatless homes, and stores can’t open because they don’t have power. Snow has fallen all the way to the beaches of Galveston. “I have never seen that,” he said.

Relative to average temperatures, the central United States was the coldest place on the planet Tuesday, Wooten said.

That degree of cold is not coming here. It’s not as though the entire hemisphere turned frigid, and when it’s that cold in one place it has to be quite warm somewhere else, Pagano pointed out. On Monday afternoon the heat index in Miami hit 92; Tuesday morning, the wind chill in the Brownsville, Texas, area, at roughly the same latitude as Miami, dropped to 12.

» READ MORE: If you think the weather at your home is colder and snowier than Philly’s official measurements, you’re probably right

The deep freeze, the result of a piece of the polar vortex that has migrated from far northern Canada, will be moderating over the next days, said Pagano.

In the meantime, the computer models have been having a cold spell of their own as they have continued to envision storm threats only to lose them and see them again or some variant thereof.

Meteorologists say that is due in part to the brisk storm traffic. It’s almost as though the atmosphere is trying to bring the nation together, with storms crashing into the West Coast, diving to the Gulf, and then spreading their wealth to the East. At one point during the weekend, winter storm advisories covered 2,500 miles from Texas to Maine, Pagano said.

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She added that the models also are having issues with the cold: “Models can struggle with something so anomalous.”

For the I-95 corridor, they don’t have much margin for error, given that about 50 million people inhabit a sliver of the planet.

Said Kines, “If you moved Philly to St. Louis, it would be so much easier.”