Mainly snow fell across Eastern Pennsylvania from the evening of the 20th into the early morning of the 21st. Snowfall averaged 1 to 2 inches in and around the local Philadelphia area and 3 to 6 inches elsewhere in Eastern Pennsylvania. Snow began in the Poconos and Lehigh Valley during the evening of the 20th and slowly spread to the south, beginning in the local Philadelphia area shortly after Midnight EST on the 21st. Some rain mixed in with the snow in the local Philadelphia area. The snow fell at its heaviest between 1 a.m. and 3 a.m. EST. The snow ended between 4 a.m. EST and 6 a.m. EST. Its greatest impact was on the morning commute in the Lehigh Valley and Poconos. A couple of accidents caused injuries in the Philadelphia northwest suburbs. An 18-year-old man was injured after he slid off of Gottschalk Road in Upper Frederick Township (Montgomery County). A 28-year-old man was pinned under a vehicle for 30 minutes after a vehicle traveling on Huffs Church Road in District Township (Berks County) swerved to avoid driving into a trash hauling truck.
Representative snowfall included 5.0 inches in Lehighton (Carbon County), 4.7 inches in Tobyhanna (Monroe County), 4.6 inches in Emmaus (Lehigh County), 4.5 inches in Bath (Northampton County), 4.4 inches at the Lehigh Valley International Airport, 4.0 inches in Bechtelsville (Berks County), Glendon (Northampton County), East Nantmeal (Chester County) and Perkasie (Bucks County), 3.1 inches in West Chester (Chester County), 3.0 inches in Royersford (Montgomery County), 2.7 inches in Bensalem (Bucks County), 2.1 inches in Wynnewood (Montgomery County), 2.0 inches in Manayunk (Philadelphia County) 1.7 inches in Drexel Hill (Delaware County) and 0.6 inches at the Philadelphia.International Airport.
The snow and wintry mix were caused by a developing low pressure system that formed in the Tennessee Valley during the afternoon of the 20th and moved northeast. It reached West Virginia at 7 p.m. EST on the 20th, the lower Susquehanna Valley in Pennsylvania at 1 a.m. EST on the 21st, right over Atlantic City, New Jersey at 4 a.m. EST on the 21st and then accelerated eastward as it strengthened. At 7 a.m. EST on the 21st, the low was already southeast of Montauk Point, New York.

Winter Weather in PHILADELPHIA, PENNSYLVANIA
From 21-JAN-11 00:30:00 to 21-JAN-11 05:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in DELAWARE, PENNSYLVANIA
From 21-JAN-11 00:30:00 to 21-JAN-11 05:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in CHESTER, PENNSYLVANIA
From 21-JAN-11 00:00:00 to 21-JAN-11 05:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in BUCKS, PENNSYLVANIA
From 21-JAN-11 00:00:00 to 21-JAN-11 06:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in LEHIGH, PENNSYLVANIA
From 20-JAN-11 20:30:00 to 21-JAN-11 05:30:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in NORTHAMPTON, PENNSYLVANIA
From 20-JAN-11 20:30:00 to 21-JAN-11 05:30:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in CARBON, PENNSYLVANIA
From 20-JAN-11 20:00:00 to 21-JAN-11 05:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in MONROE, PENNSYLVANIA
From 20-JAN-11 20:00:00 to 21-JAN-11 05:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in BERKS, PENNSYLVANIA
From 20-JAN-11 19:00:00 to 21-JAN-11 05:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in MONTGOMERY, PENNSYLVANIA
From 21-JAN-11 00:00:00 to 21-JAN-11 05:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter