A vigorous upper air disturbance coupled with a low pressure system that was intensifying east of the New Jersey coast produced heavy snow across Eastern Pennsylvania. Precipitation started again as snow across most of Eastern Pennsylvania during the late afternoon and early evening of the 20th. In and around the local Philadelphia area, where the air mass was warmer, precipitation started as rain. During the evening precipitation then changed to sleet and then snow and by 10 p.m. EST it was snowing throughout Eastern Pennsylvania.  The heaviest precipitation, thus the largest accumulation of snow fell in a band from Lancaster County northeastward through the Lehigh Valley. Accumulations ranged from three to twelve inches. The upper air disturbance was so strong that thunderstorms were reported in Delaware County and the Lehigh Valley. The snow ended shortly after daybreak on the 21st, except in the Poconos where it lingered throughout most of the morning.Because this event occurred on a Saturday night (the 20th) and a Sunday morning (the 21st), the number of traffic accidents was relatively lower. But, 30 people were injured around Noon EST on the 21st on Interstate 476 in Plymouth Meeting (Montgomery County) when a tour bus traveling from Scranton to Atlantic City attempted to pass a snow plow. While the passing the plow, the bus veered into the same lane as the plow, which struck the back of the bus and sent it into a sharp right turn into a drainage ditch.  Two of the injuries were serious.  A number of sporting events in the Poconos were cancelled for the evening of the 20th.Specific accumulations included 12 inches in Camelback Mountain (Monroe County) and Morgantown (Berks County), 10.8 inches in Williams Township (Northampton County),  8.3 inches in Reading (Berks County), 8.1 inches in Glenmoore (Chester County), 8 inches in Sellersville (Bucks County), Macungie (Lehigh County)  and Saylorsburg (Monroe County), 7.6 inches in Boyertown (Berks County),  7.5 inches in Albrightsville (Carbon County), 7 inches in at the Lehigh Valley International Airport and Pottstown and Green Lane (Montgomery County), 6.5 inches in Downingtown (Chester County), 6.3 inches in East Stroudsburg (Monroe County), 6 inches in Fricks (Bucks County), 5.3 inches in Somerton (Philadelphia), 5 inches in Wynnewood (Montgomery County), 4.5 inches in Hamburg (Berks County), Jim Thorpe (Carbon County) and Valley Forge (Chester County), 4 inches in Clifton Heights and Crum Creek (Delaware County) and 3.6 inches at the Philadelphia International Airport.

Winter Storm in CHESTER, PENNSYLVANIA
From 20-JAN-01 17:00:00 to 21-JAN-01 07:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in DELAWARE, PENNSYLVANIA
From 20-JAN-01 19:00:00 to 21-JAN-01 07:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in LEHIGH, PENNSYLVANIA
From 20-JAN-01 18:00:00 to 21-JAN-01 07:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in MONROE, PENNSYLVANIA
From 20-JAN-01 19:00:00 to 21-JAN-01 11:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in MONTGOMERY, PENNSYLVANIA
From 20-JAN-01 16:00:00 to 21-JAN-01 08:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in NORTHAMPTON, PENNSYLVANIA
From 20-JAN-01 18:00:00 to 21-JAN-01 08:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in PHILADELPHIA, PENNSYLVANIA
From 20-JAN-01 19:00:00 to 21-JAN-01 08:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in BERKS, PENNSYLVANIA
From 20-JAN-01 17:00:00 to 21-JAN-01 07:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in BUCKS, PENNSYLVANIA
From 20-JAN-01 16:00:00 to 21-JAN-01 09:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in CARBON, PENNSYLVANIA
From 20-JAN-01 16:00:00 to 21-JAN-01 10:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC