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Winter weather advisory posted for Philly for Thursday morning

The snow, sleet, and rain could mess with Thursday morning's rush hour.

A wintery mix of sleet/snow and rain  accumulated on this windshield on Nov. 19, 2016.
A wintery mix of sleet/snow and rain accumulated on this windshield on Nov. 19, 2016.Read moreELIZABETH ROBERTSON / File Photo

>> THURSDAY UPDATE: The latest on Philly's wintry mix

It has been a decade since Philadelphia officially experienced a measurable snowfall in November, but forecasters say that streak could end on Thursday.

While it is unlikely to affect the peak morning commuting period, an assortment of frozen precipitation could cause significant driving issues throughout the region as motorists have the season's first encounter with a wintry mess, and the National Weather Service has posted a winter weather advisory for the city and its neighboring counties on both sides of the river.

Forecasters said surface temperatures would flirt with freezing when precipitation from a powerful nor'easter arrives, probably at mid-morning in Philadelphia and earlier in coastal South Jersey, where gale force gusts of up to 55 mph are possible.

It likely would start as snow, and might even fall "moderately" at times, the weather service said. But warmer air will move in aloft shortly after the onset, complicating matters. Temperatures will be different at varying levels of the atmosphere, and that parfait could make for sleet, which is melted snow that refreezes before it lands, and possibly freezing rain, which freezes on contact with cold surfaces.

The upshot is at least the potential for a few hours of slippery driving. How many hours?

"That's the tough part," said Paul Fitzsimmons, a meteorologist with the National Weather Service in Mount Holly. But forecasters said they expected the precipitation to be all liquid by the peak evening commute, at least from the city south and east.

Paul Walker, senior meteorologist with AccuWeather Inc., said it's possible that areas well to the north and west of the city could see 1 to 3 inches of frozen muck before the changeover, and that a "couple of lucky spots" in and around the city could get an inch.

PennDot said it was taking no chances.

"We're already brining," department spokesman Brad Rudolph said Wednesday. "We allocated additional resources for Bucks."

Upper Bucks County is one area that could be targeted for up to 3 inches, forecasters said.

In the period of record, Philadelphia has measured a whopping 0.5 inches of snow and ice on average in November, barely beating the average for April.

And officially the city hasn't had measurable snow and ice in November since 1.0 inch on the 21st in 2008, and that was the first since 1996.

Snow or no, measurable precipitation is a certainty Thursday into Friday, meteorologists said.

Already, rainfall throughout the region is 2½ to 3 times normal for the month, and Walker said it's quite possible than when whatever it is stops falling on Friday, 2018 will become the 10th wettest year on record, with six weeks still to go.

"It has been the story of the summer," Walker said. "It's a lot of systems coming up from the south."

This particular one originated in the Gulf of Mexico and is due to intensify off the Carolina coast and become a full-blown nor'easter. In January or February, we might be in the heat of an all-out supermarket panic. Nor'easters are so named because they generate strong onshore winds from the east and northeast, and right now, ocean temperatures off New Jersey are in the low 50s.

On Thursday, the sea breeze might be the motorist's friend.