A low pressure system that just grazed extreme southeast New Jersey during the morning of the 21st brought snow to Berks County, the Lehigh Valley and the Poconos and a wintry mix of snow, sleet and freezing rain to southeastern Pennsylvania. Snowfall averaged 2 to 4 inches in southeastern Pennsylvania and 3 to 6 inches in the rest of Eastern Pennsylvania. Ice accretions in southeast Pennsylvania were one tenth of an inch or less.  While the overall number of accidents were less because this event occurred on a Saturday, a fatal accident  occurred in Philadelphia. A 21-year-old woman and a 22-year-old woman were killed in the Juniata section of the city. Two men were also injured and hospitalized. The snow and sleet caused arriving flight delays of about two hours at the Philadelphia International Airport. About thirty-five flights were cancelled. Flights were back on track on the evening of the 21st. In the Lehigh Valley, the worst reported accident occurred on Interstate 78 in Upper Macungie Township (Lehigh County) when a tractor-trailer driver lost control of his rig. The driver was not seriously injured.
Snow overspread Eastern Pennsylvania between Midnight EST and 2 a.m. EST on the 21st. In the local Philadelphia area and the nearby suburbs, the snow changed to sleet and freezing rain between 5 a.m. EST and 7 a.m. EST.  In the rest of the Philadelphia suburbs and Berks County, some sleet mixed in from time to time after 7 a.m. EST. Throughout Eastern Pennsylvania, the precipitation became spottier and lighter as the morning progressed. The snow ended around Noon EST in the Lehigh Valley and the Poconos and precipitation ended across the rest of Eastern Pennsylvania by the middle of the afternoon on the 21st.
Representative snowfall included 6.0 inches in Lake Harmony (Carbon County), 5.9 inches in East Stroudsburg (Monroe County), 5.7 inches in Tobyhanna (Monroe County), 5.5 inches in Walnutport (Northampton County), 5.0 inches in Lehighton (Carbon County) and Slatington (Lehigh County), 4.3 inches in Bethlehem (Northampton County), 4.0 inches in Boyertown (Berks County), Elverson and East Coventry (Chester County), 3.9 inches in Martins Creek (Northampton County), 3.8 inches in Eagleville (Montgomery County), 3.5 inches in East Nantmeal (Chester County), 3.4 inches at the Lehigh Valley International Airport, 3.3 inches in Hamburg (Berks County), 3.2 inches in Furlong (Bucks County), 3.0 inches in Perkasie (Bucks County) and Royersford (Montgomery County),  2.9 inches in Drexel Hill (Delaware County), 2.8 inches in West Chester (Chester County), 2.4 inches in Doylestown (Bucks County), 2.3 inches at the Philadelphia International Airport, 2.2 inches in Ridley Township (Delaware County) and Wynnewood (Montgomery County), 2.1 inches in Chester (Delaware County) and 2.0 inches in Somerton (Philadelphia County).
The low pressure system responsible for the wintry mix formed on a cold front over the Southern Plains on the 20th. At 7 p.m. EST on the 20th, it reached Arkansas. It moved northeast and reached Kentucky at 1 a.m. EST on the 21st, the lower Chesapeake Bay at 7 a.m. EST on the 21st, just east of Cape May, New Jersey at 10 a.m. EST on the 21st and about 100 miles east of the New Jersey coast at 1 p.m. EST on the 21st. The track of the low pressure system made it difficult for warm air to move in at the surface, even if it warmed enough aloft to change the snow to either sleet or freezing rain in the southeast part of the state.

Winter Weather in BERKS, PENNSYLVANIA
From 21-JAN-12 01:00:00 to 21-JAN-12 15:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in CARBON, PENNSYLVANIA
From 21-JAN-12 00:00:00 to 21-JAN-12 13:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in MONROE, PENNSYLVANIA
From 21-JAN-12 00:00:00 to 21-JAN-12 13:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in LEHIGH, PENNSYLVANIA
From 21-JAN-12 02:00:00 to 21-JAN-12 12:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in NORTHAMPTON, PENNSYLVANIA
From 21-JAN-12 02:00:00 to 21-JAN-12 12:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in BUCKS, PENNSYLVANIA
From 21-JAN-12 02:00:00 to 21-JAN-12 15:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in DELAWARE, PENNSYLVANIA
From 21-JAN-12 02:00:00 to 21-JAN-12 15:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in PHILADELPHIA, PENNSYLVANIA
From 21-JAN-12 02:00:00 to 21-JAN-12 15:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in MONTGOMERY, PENNSYLVANIA
From 21-JAN-12 01:00:00 to 21-JAN-12 15:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in CHESTER, PENNSYLVANIA
From 21-JAN-12 01:00:00 to 21-JAN-12 15:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter