A protracted winter storm with a one-two punch affected Eastern Pennsylvania from the early morning of the 26th into the early morning of the 27th. This was the heaviest single snow event of the season for both Philadelphia and Allentown and included thundersnow in and around Philadelphia during the evening of the 26th. Snow and sleet accumulations averaged 12 to 16 inches around the local Philadelphia area, around 12 inches in Berks County and the Lehigh Valley and 3 to 8 inches in the Poconos.
Around Philadelphia and the northwest suburbs, precipitation began as snow just before the start of the morning commute on the 26th. The snow fell heavy at times during the morning in the northwest suburbs as several inches accumulated. The snow changed to sleet and rain (some pockets of freezing rain in Bucks County) close to Noon EST.  Precipitation became spottier during the afternoon. Steadier rain started again late in the afternoon on the 26th and changed quickly to sleet and snow around 6 p.m. EST. The snow fell heavy at times during the evening and ended around 2 a.m. EST on the 27th. In Berks County and the Lehigh Valley precipitation began as snow during the start of the morning commute on the 26th. The snow changed to a spottier mixture of sleet and freezing rain during the early afternoon. Precipitation changed back to all snow by 6 p.m. EST on the 26th and fell heavy at times during the evening. The snow ended around 2 a.m. EST on the 27th. Across the Poconos, snow began around 6 a.m. EST on the 26th, fell heavy at times during the late afternoon and evening and ended around Midnight EST on the 27th.
The one-two punch hit the local Philadelphia the hardest. Many municipalities declared snow emergencies. There were more than three dozen accidents during the morning of the 26th. This included an ambulance on its way to a hospital with a patient in West Nantmeal Township (Chester County). No injuries were reported. SEPTA regional transportation reported service disruptions along with systemwide delays. Philadelphia International Airport had 41 morning flights cancelled and had average delays of three hours. With the first surge of snow on the morning of the 26th, many school districts made last minute decisions to either close or have delayed openings. Many closed early that afternoon. Even Saint Joseph's University and West Chester University closed.
Conditions though became worse when the second punch of heavier snow came through on the evening of the 26th. Snowfall rates reached 2 to 4 inches per hour. In Philadelphia, the emergency 311 hot line had four times the normal rate of calls. Many vehicles and buses were stuck in the snow. Some SEPTA bus drivers were stranded up to twelve hours. SEPTA still had service suspended on about one third of its routes on the 28th. About 1,500 travelers were stranded overnight on the 26th at Philadelphia International Airport. Schools and courts were closed on the 27th. Schools were also closed on the 28th. In the northwest suburbs, numerous crashes were reported in Berks, Chester and Montgomery Counties on Pennsylvania State Routes 100 and 29 as well as U.S. Routes 202 and 422. In West Pottsgrove (Montgomery County), a 45-year-old man was injured after his vehicle slid down an embankment on Westbound U.S. Route 422 and rolled over.  In Northampton County, westbound Interstate 78 was closed for three hours overnight on the 26th between Pennsylvania State Routes 412 and 309 because of disabled commercial vehicles. The weight of the snow also downed some trees in the southeast part of the state, but power outages remained isolated. The continued onslaught of winter weather was causing numerous municipalities to exhaust their snow removal budgets. The city of Philadelphia estimated the clean-up costs from the latest winter storm was at least 6 million dollars.
Representative snowfall included 16.9 inches in Bensalem (Bucks County), 16.4 inches in Royersford (Montgomery County), 16.1 inches in Downingtown (Chester County), 15.3 inches in Kennett Square (Chester County) and Drexel Hill (Delaware County), 15.1 inches at the Philadelphia International Airport, 14.8 inches in Perkasie (Bucks County) and Abington (Montgomery County), 14.0 inches in Exton (Chester County), 12.9 inches in Clifton Heights (Delaware County), 11.6 inches at the Lehigh Valley International Airport, 11.1 inches in Huffs Church (Berks County), 11.0 inches in Bethlehem (Northampton County), 10.8 inches in Shillington (Berks County), 9.2 inches in Schnecksville (Lehigh County), 8.5 inches in Martins Creek (Northampton County), 8.2 inches in East Stroudsburg (Monroe County), 4.4 inches in Tobyhanna (Monroe County),  2.9 inches in Bowmanstown and 2.5 inches in Palmerton.
The latest winter storm was caused by a low pressure system that emerged from the western Gulf of Mexico on the 25th and moved northeast to Cape Hatteras, North Carolina at 7 a.m. EST on the 26th. From there it turned slightly more to the northnortheast and passed through the Delmarva coastal waters during the afternoon and early evening on the 26th and then continued northeast and passed just south of Cape Cod, Massachusetts early on the 27th. The turn more toward the coast permitted some warmer air to reach into southeastern Pennsylvania during the day on the 26th. The heavy snow burst was triggered by the surface low's upper air support that passed through the state on the evening of the 26th.

Winter Storm in DELAWARE, PENNSYLVANIA
From 26-JAN-11 05:00:00 to 27-JAN-11 02:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in MONTGOMERY, PENNSYLVANIA
From 26-JAN-11 05:00:00 to 27-JAN-11 02:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in PHILADELPHIA, PENNSYLVANIA
From 26-JAN-11 05:00:00 to 27-JAN-11 02:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in BUCKS, PENNSYLVANIA
From 26-JAN-11 06:00:00 to 27-JAN-11 03:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in LEHIGH, PENNSYLVANIA
From 26-JAN-11 07:00:00 to 27-JAN-11 02:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in NORTHAMPTON, PENNSYLVANIA
From 26-JAN-11 07:00:00 to 27-JAN-11 02:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in CARBON, PENNSYLVANIA
From 26-JAN-11 06:00:00 to 27-JAN-11 00:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Heavy Snow in MONROE, PENNSYLVANIA
From 26-JAN-11 06:00:00 to 27-JAN-11 00:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in BERKS, PENNSYLVANIA
From 26-JAN-11 05:00:00 to 27-JAN-11 01:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in CHESTER, PENNSYLVANIA
From 26-JAN-11 04:00:00 to 27-JAN-11 01:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter