Philly area can expect a prolonged period of sleet and freezing rain Thursday into Friday

A major lacquering isn’t expected, nor are widespread power outages, but a prolonged period of freezing rain and sleet is likely to put areas west of the Delaware River on ice late Thursday night and Friday morning.

The National Weather Service has posted a winter weather advisory for Bucks, Chester, and Montgomery Counties from 7 p.m. until 10 a.m., and until 4 a.m. in Philly and Delaware County. In some areas north and west of the city, “several hours of freezing rain” was expected, the agency said.

A renegade piece of the main storm did generate some harmless light snow and sleet across the region during the late morning into the afternoon, but the steady precipitation wasn’t due until Thursday night.

In a month that has had trouble choosing seasons it belonged, the temperature reached 70 degrees Wednesday, normal for a May 1, and didn’t get past the mid-30s Thursday throughout the region. Even for a month that is traditionally volatile, February 2022 has been extraordinary.

Readings overnight were forecast to remain near or below freezing, and icing could become an issue on the roads, at least in parts of Philly’s neighboring counties.

» READ MORE: In Philly winters, expect anything

While paved surfaces have been cooked by temperatures well above normal this month, they got a chilling overnight with readings falling into the 20s early Thursday.

Roads could become coated with a layer of sleet Thursday night before the precipitation mutates to freezing rain that would continue until about daybreak Friday, said Alex Staarmann, a meteorologist in the Mount Holly office.

It’s at least possible the steady precipitation could start as a “burst of snow,” said Paul Walker, senior meteorologist with AccuWeather Inc.

Ice accruals of about 0.1 to 0.2 inches were forecast for Bucks, Chester, and Montgomery Counties, with lesser amounts in Philly, Delaware County, and adjacent South Jersey. Any accumulations of ice would qualify as “advisory” levels, Staarmann said.

The fact that a significant portion of the ice would fall as sleet would argue against mass power outages, he said. Those tiny ice rocks bounce off wires and tree branches, as opposed to rain that freezes on contact and forms dangerous, weighty layers of ice.

It remained uncertain just how quickly the icing would yield to liquid rain come Friday morning as temperatures are expected to creep above freezing and into the 40s in the afternoon. “It will be a pretty slow transition south to north,” Staarmann said.

The storm system is a complex one. It is forecast to approach the Ohio Valley, warming the upper atmosphere as it approaches, and then spawn a secondary low somewhere near New Jersey, forecasters said.

Meanwhile, some of the cold air pouring into the region behind a front that came through Wednesday will remain “dammed” at the surface east of the Appalachians, holding its ground against approaching warm air.

The region will be under a rather unappealing atmospheric parfait with different temperatures at different levels, with the air warmer aloft, thus the wintry mix.

» READ MORE: Road brining before winter storms is gaining more traction

When the freezing layer is thick enough, raindrops freeze on the way down and become sleet. If that layer is thin, the rain won’t freeze until it reaches the surface. In terms of driving and potential power outages, freezing rain is far more dangerous.

Once the mess clears out, no more precipitation is expected for the next several days and conditions could feature something completely different from the rest of the month — a run of seasonally appropriate temperatures.

Thursday marked the fifth time this month that high temperatures will have been 20 degrees different from those of the previous day. In the 1,730 months of record-keeping dating to 1874, that has occurred only nine times.

» READ MORE: Philly's winter weather is usually wacky. But not this wacky.

Staff writer Aseem Shukla contributed to this article.

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