Snow amounts jump as Lehigh Valley comes under winter weather watch

BETHLEHEM, Pa. — It looks more and more like we might be on the cusp of the biggest storm of the winter season.

The National Weather Service on Friday afternoon placed the Lehigh Valley and southeastern Pennsylvania under a winter weather watch that lasts from 7 a.m. Sunday to 10 p.m. Sunday.

Total snow accumulations between 5 and 8 inches are possible, according to the weather service.

It's a precursor to what will also bring the coldest air of the season next week.

The computer models have been closely watched by forecasters — and sportscasters — as a storm system develops along an Arctic cold front that will pass through the region just in time for the Philadelphia Eagles home playoff game at Lincoln Financial Field.

Depending on how the system evolves, a robust and plowable storm seems like the more likely scenario.

Then, extreme cold will overspread the area and hang around through Wednesday, meteorologists say.

A breakdown of storm potential

Computer models have varied significantly for how much snow will fall Sunday.

Meteorologists have been eyeing a number of things over the past few days:

• Model variances and the track of the storm
• The development of the coastal low expected 
• The timing of the Arctic front approaching 

EPAWA meteorologist Bobby Martrich described models coming on board with “hit after hit after hit” on Thursday, following what appeared to be an outlier in the Canadian model.

It progressively depicted a snowstorm for the region days ago, with the main models (the GFS and the Euro) later coming on board.

Ultimately, the track and strength of the surface low will determine what type and how much precipitation the area experiences, forecasters say.

If the track of the low is close enough to the coast, a large part of the region will see accumulating snowfall.

If the track of the low hugs the coast, or ends up just inland over the coastal plain, the most significant snow will be focused north and west of Interstate 95, including the Lehigh Valley.

“The greatest potential for significant accumulations remains for areas along the I-95 corridor and points north and west,” the National Weather Service said in its latest forecast discussion.

Martrich said some models, including the short-range Canadian model that ran late Thursday night, shows a storm that “ramps up” and dumps a lot of heavy snow in our area, with less in Philadelphia.

“Keep that stuff away from Philadelphia,” he jokingly said, with kickoff for the Eagles game set for 3 p.m. Sunday.

Brutal cold to follow

Regardless of snowfall totals, the bigger concern is the heart of the Arctic air mass coming behind it.

Forecasters say the peak of the cold looks to occur during the Monday night through Wednesday night timeframe, with high temperatures mostly in the low 20s or teens and low temps in the single digits or below zero (especially north of Interstate 78).

The coldest daytime periods will be Tuesday and Wednesday, with highs in the teens and wind chills in the single digits during the day and below zero at night.

The weather service expects to issue cold weather advisories and warnings in the coming days, with “feels like” temperatures as low as -20 degrees in the Poconos.