Thursday, December 25, 2014

Snow starting

First flakes officially observed at Philly airport.

Snow starting

It took awhile but att noon light snow was falling northwest of the city and a mix of snow and rain was detected at Philadelphia International Airport as the precipitation finally battles through a wall of dry air.

As precipitation falls into the dry air, temperatures should drop. They fell from 42 at 11 a.m. to 38 at noon at the airport.

The National Weather Service continues its winter advisories for the region and is calling for 4 to 6 inches from this premature winter storm.

In the morning discussion, the weather service says that all the models now see a so-called "trowal" setting up over eastern Pennsylvania and South Jersey.

The position of the trowal -- an area of warm, moist air aloft -- has a big influence on where the heaviest snow falls.

Expect light precipitation the next few hours, but things should pick up by mid-afternoon.

Temperatures are forecast to remain above freezing, however roads could be become a problem late this afternoon and this evening.

Snow can stick even if temperatures remain above freezing, providing it snows hard enough. A quick layer of snow can provide a cold, white carpet, perfect for further accumulation.

Tony Wood Inquirer Weather Columnist
About this blog

Everyone talks about the weather, and here we write about it.

When we’re around and conditions warrant, we’ll keep you updated about what’s coming, but we will do our best always to discuss weather and climate developments in context and remind you that nothing in the atmosphere happens in a vacuum.

Tony Wood has been writing about the atmosphere for The Inquirer for 26 years.

Reach Tony at twood@phillynews.com.

Tony Wood Inquirer Weather Columnist
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