Winter weather advisory in effect as messy, uncertain storm moves in

BETHLEHEM, Pa. — A winter weather advisory remains in effect from 1 p.m. Friday through 10 a.m. Saturday for parts of eastern Pennsylvania, as an impactful — but highly uncertain — winter storm moves into the region.

After days of updates, forecasters say the overall message is not how much snow or sleet could fall, but how difficult travel could become, especially Friday night.

Arrival time in the Lehigh Valley is expected to be late afternoon, somewhere between 4 and 5 p.m.

But while cold air will be in place at the surface, warmer air higher up in the atmosphere could change snow to sleet for most locations.

Exactly how far north that “warn nose” nudges remains unclear, and meteorologists warn small shifts could make a huge difference in what people experience on the ground.

That uncertainty is why forecast confidence in specific totals has shifted over the past 48 hours, and why it remains low.

A most likely scenario?

In general, forecasters say areas north of Interstate 78 are more likely to see mostly snow, while areas between Philadelphia and Interstate 78 could see a mix of snow and sleet.

Further south and east — including much of the Philadelphia metro area and South Jersey — precipitation is likely to change to rain after a brief period of wintry precipitation.

Snow and sleet totals of 1 to 3 inches are possible in advisory areas, with a light glaze of ice in spots, the National Weather Service said Friday morning.

Some locations north of I-78 could see higher amounts if a narrow band of heavier snow develops Friday evening.

If that band sets up, snowfall rates could briefly reach 1 to 2 inches an hour — but forecasters stressed that its exact location was uncertain.

In the Allentown area, a prolonged mix of sleet and snow is expected, with a light glaze of ice possible.

Around Philadelphia and into South Jersey, accumulations should be lighter, but slippery conditions still are likely, because of the mix of precipitation types.

Travel considerations

Because the storm will unfold during peak travel hours and overnight, even modest snow or ice could cause significant problems on roads.

Forecasters emphasized again to focus on overall impacts, and that regardless of exact totals, conditions could deteriorate quickly.

Drivers are urged to use caution, allow extra time and stay alert for changing conditions as the forecast evolves, particularly because of volume expected from post-Christmas travel.

"This isn't going to be a prolonged event, but when you're talking about any kind of ice, whether it's freezing rain or sleet, that's the kind of stuff you want to avoid," EPAWA meteorologist Bobby Martrich said in his latest video update.

Martrich emphasized the event remains a "boom or bust" scenario.

Ahead of the storm, the state Transportation Department and the Pennsylvania Turnpike Commission have implemented vehicle restrictions across major roadways.

The following vehicle restrictions are planned to go into effect at 2 p.m. in accordance with Tier 3 of the commonwealth’s weather event vehicle restriction plan.

• I-81, north of I-83
• Route 33, entire length
• U.S. 22 between I-78 to Route 33
• ALL Pennsylvania interstates east of I-81.
• PA Turnpike I-76
• All eastern PA Turnpike extensions

On roadways with Tier 3 restrictions in place, no commercial vehicles are permitted except loaded single trailers with chains or approved alternate traction devices.

Additionally, all school buses, commercial buses, motor coaches, motorcycles, RVs/motorhomes and passenger vehicles (cars, SUVs, pickup trucks, etc.) towing trailers are not permitted on affected roadways while restrictions are in place.

Speed limits will be restricted to 45 mph on those roadways for all vehicles while the vehicle restrictions are in place, and commercial vehicles not affected by the restrictions must move to the right lane.

Additional speed restrictions on other interstates could be added depending on changing conditions, PennDOT said.