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Monday, December 31, 2007

Icy Morning, Mild End of 2007

At 2:30 this morning, some snow showed up on our regional radar. Only snow on the ground was north of Shrewsbury, PA. So if you took my map from yesterday and shifted it north about 20 miles, it fits. Otherwise, it was just wet.
This morning- ICY ROADS- became a problem after 5am. That's when temps dropped near freezing, and the JFX proved itself as an ice rink.
Since most of I-83 (JFX) is elevated, it is more susceptible to freezing, like many bridges and ramps.

One of the most frequent winter questions I get is about this. "Why do bridges and overpasses freeze first"? This is primarily due to cold air passing both above and below the road surface. So there is no insulating from the ground. Add in some moisture from a wet road evaporating, and this will further cool down the surface. As a result, even when the air is just above freezing, elevated surfaces and freeze.

We should have a sunny day, with a finish in the upper 40s. Not much to say about New Year's night as next weather system approaches. We should cloud up, but be in the mid 30s at midnight. Light snow or rain will move in by daybreak, so late party folk may want to think twice. My forecast maps are available on the TV Graphics page. I left my computer at home- with my snow records on it... so I will post the 1990s on New Years Day for you to view while surfing Bowl games.

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