A wintry mix of precipitation affected most of Eastern Pennsylvania except for Philadelphia and its immediate suburbs from the afternoon of the 18th into the morning of the 19th. In Berks County, the Lehigh Valley and the Poconos, snowfall averaged two to six inches and ice accretions average one to three tenths of an inch, highest in the southern Poconos. In the Philadelphia northern suburbs snowfall averaged around an inch and little if any snow accumulated toward Philadelphia. Untreated roadways were hazardous. It was snowing heavily during the evening commute on the 18th.
Precipitation started as snow during the mid to late afternoon on the 18th and fell at its heaviest during that evening commute. In the Philadelphia northern suburbs and Berks County, the snow changed to rain by the middle of that evening.  In the Lehigh Valley and Poconos, the snow changed to sleet and then to freezing rain that evening. In the Lehigh Valley, the freezing rain changed to plain rain early on the 19th, but a wintry mix of snow, sleet and freezing rain persisted in the Poconos until precipitation ended on the morning of the 19th. Travel was particularly difficult in the Poconos and accidents were reported in Monroe County. Traffic was reported as difficult along Pennsylvania State Routes 115 and 715 and U.S. Route 209.
Representative snowfall included 6.0 inches in Summit Hill and Lake Harmony in Carbon County, 5.8 inches in Tobyhanna (Monroe County), 5.0 inches in Mount Pocono (Monroe County), 4.0 inches in Bowmanstown (Carbon County) and New Tripoli and Schnecksville in Lehigh County, 3.5 inches in Saylorsburg (Monroe County), 3.2 inches in Bethlehem (Northampton County) and Jim Thorpe (Carbon County), 3.0 inches in Bernville (Berks County) and Danielsville (Northamptobn County), 2.7 inches in East Stroudsburg (Monroe County), 2.5 inches in Martins Creek (Northampton County), 2.3 inches in Reading (Berks County), 1.9 inches at the Lehigh Valley International Airport, 1.5 inches in Glendon (Northampton County), 1.3 inches in Elverson (Chester County), 1.2 inches in Gilbertsville (Montgomery County) and 1.0 inch in Doylestown (Bucks County) and Harleysville (Montgomery County).  Representative ice accumulations included 0.3 of an inch in Pocono Summit (Monroe County), 0.25 inches in Stormville (Monroe County) and 0.1 inches in Summit Hill (Carbon County).
The wintry weather was caused by a low pressure system that moved from the Southern Plains on the morning of the 17th eastnortheast and reached the Tennessee Valley on the morning of the 18th and the Ohio Valley on the evening of the 18th. A secondary low pressure system formed on the system's warm front along the Carolina coast overnight on the 18th. This low slowly became the primary low pressure system as it moved northeast and passed east of the New Jersey coast on the morning of the 19th. A high pressure system paralleled the track of the low as it moved from the Great Lakes on the morning of the 17th and into New England on the morning of the 18th. It kept initially dry and then sufficiently cold air in place near the surface to perpetuate the wintry precipitation, especially in the Poconos.

Winter Weather in LEHIGH, PENNSYLVANIA
From 18-MAR-13 15:00:00 to 19-MAR-13 01:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Winter Weather in NORTHAMPTON, PENNSYLVANIA
From 18-MAR-13 15:00:00 to 19-MAR-13 01:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Winter Storm in MONROE, PENNSYLVANIA
From 18-MAR-13 14:00:00 to 19-MAR-13 10:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in CARBON, PENNSYLVANIA
From 18-MAR-13 14:00:00 to 19-MAR-13 10:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Weather in WESTERN CHESTER, PENNSYLVANIA
From 18-MAR-13 16:00:00 to 18-MAR-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Winter Weather in WESTERN MONTGOMERY, PENNSYLVANIA
From 18-MAR-13 16:00:00 to 18-MAR-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Winter Weather in LOWER BUCKS, PENNSYLVANIA
From 18-MAR-13 16:00:00 to 18-MAR-13 19:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Winter Weather in UPPER BUCKS, PENNSYLVANIA
From 18-MAR-13 16:00:00 to 18-MAR-13 23:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Winter Weather in BERKS, PENNSYLVANIA
From 18-MAR-13 15:00:00 to 18-MAR-13 20:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS