Forecasters: Another ‘sneaky’ snow event could help usher in the winter solstice

BETHLEHEM, Pa. — A low-impact system Friday night could bring the Lehigh Valley measurable snow for the second time this week, forecasters say.

It comes after the area saw a coating late Sunday night — the first measurable snow of meteorological winter, which runs December through February.

Forecast guidance continues to indicate precipitation can be expected over the region Friday evening, which could leave a blanket of white in some areas as we await the winter solstice.

The solstice marks the shortest day and longest night of the year in the Northern Hemisphere. After that, days will get a little bit longer every single day until late June.

The solstice is the official start of astronomical winter, which runs from Saturday until the arrival of the spring equinox on March 20, 2025.

The setup

Multiple sources say a decaying clipper will bring light snow to many areas, with low confidence in a potential narrow corridor of snow that could be heavier.

That corridor could include the Lehigh Valley area, according to a graphic shared on X by meteorologist Tomer Burg.

The graphic highlights an area of “moderate potential” for minor snow accumulation based on an inverted trough.

What is an inverted trough?

The National Weather Service says a deepening upper trough will approach the area to close the week.

At the same time, a secondary system will develop off the mid-Atlantic coast and deepen rapidly as it lifts northeast.

“With the low offshore remaining in ‘close enough’ proximity to the area, it is looking more likely that there will be some areas of light rain and snow across the area on Friday into Friday night,” the weather service said in its latest forecast discussion.

In addition, some forecast guidance indicates the development of an inverted/Norlun trough set-up on the northwest side of the offshore low.

That would enhance precipitation across portions of the area,” the discussion said.

Norlun troughs tend to produce a narrow axis of heavier snow, creating a very localized storm.

“It could bring parts of the region — in a very narrow corridor — some snow, and accumulating snow at that, but just not a lot,” EPAWA meteorologist Bobby Martrich said in his latest video update.

“There’s kind of a weak inverted trough signature there, but there is an inverted trough nevertheless,” Martrich said, noting no notable wind direction shift in this case that's usually present during a Norlun trough, which is a very specific type of inverted trough.

Valley among ‘best chance’ of snow areas

The weather service said it remains uncertain “where or if this feature is to even develop at this time,” but highlighted several areas that have the best chance of observing accumulating snow.

Those areas include the Lehigh Valley, northern New Jersey and in the Poconos, where temperatures will be cooler through the duration of the event.

“Snow totals in these areas will range between 1-2 inches, locally up to 3 inches," the NWS forecast discussion said.

"Light accumulations of a dusting up to one inch are possible across the remainder of New Jersey.”

Martrich said those types of setups are “notoriously difficult to forecast,” with areas to the west and east of the corridor “getting absolutely nothing.”