Winter Storm in Pennsylvania, December 11, 2002

A winter storm of sleet and freezing rain affected the northern Philadelphia suburbs, Berks County and the Lehigh Valley. Freezing rain and sleet also fell in the Poconos, but precipitation changed to snow before it ended during the evening of the 11th. About 12,000 Eastern Pennsylvania residents lost power, mainly from freezing rain and sleet accruing to exposed surfaces and taking down tree limbs and subsequently power lines. While it was warm enough aloft for precipitation to fall as rain, enough cold air was left at or near the surface by a departing high pressure system for the rain to freeze on contact or for precipitation to fall as sleet. Precipitation (in the form of sleet and freezing rain) spread from south to north across the area between 5 a.m. and 8 a.m. EST. In upper sections of Montgomery, Chester and Bucks Counties, surface temperatures remained below freezing throughout the morning and about a quarter of an inch of ice accrued to exposed surfaces. Farther south in those counties, precipitation just briefly fell as freezing rain or sleet before temperatures rose above freezing. The change to plain rain took longer (into the middle of the afternoon) across Berks County and the Lehigh Valley. The changeover was also elevation dependent. Higher terrain locations took longer to change to plain rain. In the Poconos, some valley locations changed to plain rain during the afternoon, otherwise a wintry mix continued. Ice accretions in the Lehigh Valley averaged around one quarter of an inch and in Berks County and the Poconos averaged between one quarter and one half of an inch. A couple of inches of snow then accumulated across higher terrain locations of the Poconos during the evening of the 11th. Precipitation ended late in the evening on the 11th. In Berks County, numerous minor accidents occurred. Most schools, government offices and businesses closed because of the ice. About 6,200 Metropolitan Edison and Pennsylvania Power and Light (PPL) customers lost power because of downed power lines by tree limbs. Power was restored during the evening of the 12th. In the Poconos, numerous accidents also occurred. In Stroudsburg (Monroe County) two pickup trucks crashed head on and a woman flipped her car on Pennsylvania State Route 191. Traffic moved at a crawl through the Delaware Water Gap National Recreation area. Vehicles slid into ditches on Interstate 80. Many schools were closed and most had delayed openings on the 12th. Evening events were postponed. About 5,000 PPL customers lost power. The number was down to 2,000 on the 12th with full restoration on the 13th. The snow during the evening of the 11th slowed the restoration process. A large high pressure system from central Canada brought in cold, dry air into the region. As a low pressure system formed in the Gulf of Mexico on the 10th, it started to push moisture north into the region. As the high retreated into New England, the low moved northeast along the Atlantic Seaboard from near Myrtle Beach the morning of the 11th to near Cape Cod the morning of the 12th. Enough warm air moved westward from the Atlantic to change precipitation to plain rain along the coastal plain. But, the cold air became entrenched, especially over the Poconos, Berks County and the Lehigh Valley and was difficult to displace throughout this event.