Threatening the region with up to 10 inches of  wet, heavy snow, wind gusts to 40 mph, and fresh rounds of power outages, another potent nor'easter in all likelihood will be a "dangerous" sequel to Friday's "bomb" cyclone, forecasters warned Tuesday.

As is typical with March storms, snow totals on Wednesday were uncertain, dependent on temperatures, elevations, and how hard it snows; however, the adhesive nature of wet snow, its sheer water weight, and gale-force gusts were almost certain to bring down more wires, branches, and perhaps trees.

The National Weather Service advised that "very heavy snow" would create "dangerous conditions and an increasing risk for tree and power line damage." It recommended that people not travel after 7 a.m.

Rain crept into the region Tuesday evening, and turned to wet snow later. It was forecast to become heavy on Wednesday,  with as much as 1 to 2 inches an hour expected to fall from 10 a.m. to 6 p.m., the weather service said. A winter-storm warning was in effect for Philadelphia and the Pennsylvania suburbs, and an advisory for adjacent South Jersey.

After a February that at times felt more like May, this could become one of the region's most-disruptive winter-weather weeks in the period of record.

And well before the first wet flakes fell, the storm already was having an impact Tuesday.

Officials announced that all Philadelphia schools and government offices would be closed Wednesday. SEPTA Regional Rail will be on a Saturday schedule, and the agency advised commuters not to use transit unless they have to. It said about half the 118 bus routes could be detoured. PATCO said its trains would run more slowly. Gov. Wolf imposed tractor-trailer restrictions on state highways.

>> READ MORE: Info on transit, utilities, school closings and more ahead of Wednesday's snow

Only minor coastal flooding was forecast at the Shore, but the big concern this time around is the potential for more mass power outages. New Jersey Gov. Murphy declared a state of emergency Tuesday night.

Friday's storm knocked out power to 630,000 customers, affecting over a million people, and better than 17,000 customers still were without it Tuesday evening. Customers still awaiting a repair crew were growing increasingly frustrated. Steven Kline, an Abington Township commissioner, said residents in the Meadowbrook area always seem to be the last to get service.

Peco has recruited "foreign workers" — the official term for crews from other utilities — from the South to help with the restorations, and it looks like they're sticking around.

"We're going to keep those crews on hand throughout," said Greg Smore, a Peco spokesman.

Compounding the power outage threat is the fact the ground is thoroughly wet.  Last month was one of the wettest Februaries on record in Philadelphia, and the remnants of Friday's snow have seeped into the soil, making tree roots that much more vulnerable.

Wednesday's storm could slow restoration efforts with a new thick layer of snow and additional downed trees impeding repair crews, Smore said.

The heaviest snows were expected to fall on the "fall line," the elevated areas to the northwest of the city.

Temperatures in and around the city likely will stay near or above freezing, and those borderline readings could affect accumulations, said Dave Dombek, a meteorologist with AccuWeather Inc. Near the city, he said, "I kind of like the 6 rather than the 10. I think you'll struggle to reach double-digits."

The expected snowfall for the Philadelphia region for Wednesday’s storm as of Tuesday night.
National Weather Service
The expected snowfall for the Philadelphia region for Wednesday’s storm as of Tuesday night.

Along with elevation and temperature, the key to accumulations will be how heavily the precipitation falls. Heavy snow cools the atmosphere; when the precipitation lets up, it's more likely to change to a rainy mix.

"We saw that last week," said Dombek.

Regardless of what happens, the last several days have represented a remarkable winter revival as a profound pattern change has taken hold.

It was signaled by snow in Rome and the British Isles late last month, evidence that for the first time in several weeks a "blocking" pattern was emerging in the North Atlantic, driving cold into Western Europe and eventually into the Northeastern United States.

Air pressure near Greenland became higher than normal, and along with delivering the cold needed for snowfall, it served to get in the way of storms that otherwise would scoot out to sea. The pattern technically is known as the negative phase of the North Atlantic Oscillation, which is measured by an index.

That index went negative at the end of February, and reached a seasonal low on Friday, according to the Climate Prediction Center.

The changes were kick-started by significant changes in the upper atmosphere over the Arctic in early February, said Walt Drag, a lead forecaster at the National Weather Service Office in Mount Holly

The pattern is likely to persist at least for several days and more storm threats are likely, Drag said, including one early next week.

Said Drag: "It's not over yet."

Staff writers Joseph A. Gambardello, Jason Laughlin, and Andrew Seidman contributed to this article.