BETHLEHEM, Pa. — If a white Christmas topped your list to Santa this year, it looks like the big guy is doing his best to deliver, even if it may be a day behind schedule.
Christmas Day is expected to be snow-free, but a developing storm could bring a wintry mess on Dec. 26, forecasters say.
In fact, the National Weather Service says confidence is growing that multiple storm systems will affect the region over the coming days, even as uncertainty remains about exact timing, storm tracks and precipitation types.
The news arrived with parts of the Lehigh Valley under a winter weather advisory Tuesday, with the highest snow amounts and greatest potential for a glaze of ice at elevations above 1,000 feet.
But many already are looking ahead.
A wintry mix?
The first system of interest has the potential to arrive Friday afternoon and continue into early Saturday, driven by a disturbance in northwesterly flow aloft.
At the surface, low pressure is forecast to move out of the Ohio Valley toward the Mid-Atlantic, with the potential for a secondary low to develop offshore Friday night.
Where that secondary low forms remains a key question. Forecast models show a wide range of possibilities, from off the North Carolina coast to east of New Jersey.
That track will depend heavily on the strength and position of a large area of high pressure — locking in cold air — centered over Quebec, and how quickly it shifts northeast.
Recent forecast trends favor a stronger, more persistent high-pressure system, which would push the developing coastal low farther south and let colder air remain in place across eastern Pennsylvania.
As a result, forecasters say the likelihood of impactful wintry precipitation — including snow — is increasing, though it's still too early to determine exact snowfall amounts or whether the Lehigh Valley will see mostly snow, a mix or rain.
'An overrunning event'
"This is going to be an overrunning event,” EPAWA meteorologist Bobby Martrich said in his latest video update.
"So it’s going to be running into cold air at the surface, but aloft is still going to have a little bit of a warm wedge in there.
"So you’re going to start off as snow, we think, in most areas, and then you’re going to go over to a wintry mix, maybe some freezing rain."
If the colder scenario verifies, snow could arrive on Dec. 26, narrowly missing Christmas Day.
“This exact breakdown of how that’s going to work out, the devil is still in the details with that," Martrich said.
“This exact breakdown of how that’s going to work out, the devil is still in the details."Meteorologist Bobby Martrich
“How much snow we could get versus ice, or whatever and for where, that all has to be worked out over the next couple of days.”
The unsettled pattern is expected to continue into the weekend, with another system possible Sunday. That also could bring a range of weather impacts to different parts of the region, but forecasters say it’s far too early for any details.
Martrich said a first call from his team on Friday’s storm would come on Christmas Eve.
