A low pressure system from the southern plains combined with a cold front from the upper Mississippi Valley to bring a wintry mix of precipitation across most of eastern Pennsylvania from the evening of the 17th through the afternoon of the 18th. Precipitation began as snow across the region during the evening of the 17th. After midnight EST, some sleet started to mix in, especially near Philadelphia. The mixing with sleet took much of the night to reach the Poconos.  As more warmer air moved in aloft, precipitation started mixing with and changing to freezing rain after 5 a.m. EST on the 18th. Precipitation in the Poconos remained a wintry mix through the first half of the morning. Near Philadelphia, enough warm air moved in near the surface to change the precipitation to plain rain during the morning of the 18th. As a cold front approached the region and precipitation intensity increased, the changeover process reversed itself. Precipitation changed to all snow by the middle of the morning in the Poconos and the Lehigh Valley and in Berks County and the Philadelphia northwest suburbs around Noon EST. The snow ended during the afternoon of the 18th. Snowfall accumulations averaged between 2 and 5 inches and ice accretions averaged around one tenth of an inch.Untreated roads became very hazardous and slippery, especially since the recent weather was unseasonably cold. Many accidents occurred on the 18th. A fatal accident occurred on Pennsylvania State Route 73 in Ruscombmanor Township (Berks County). A 61-year-old man, 65-year-old man and 64-year-old man were killed when the driver of their Sports Utility Vehicle lost control in the westbound lane, skidded off the road, bounced off a guard rail and hit a tree twenty feet down an embankment. Elsewhere in Berks County, the westbound lanes of Interstate 78 were closed for two and a half hours after a tractor-trailer driver lost control and struck the center median in Greenwich Township. In Lehigh County, a 47-year-old Slatington woman was critically injured after she skidded and struck a tree. In Northampton County, five people were injured in a three vehicle crash on Pennsylvania State Route 33. Interstate 78 was closed in Williams Township when a truck containing hazardous material jackknifed. In Montgomery County, many accidents occurred on Pennsylvania State Route 100 and U.S. Route 422. Cars skidded into each other, guardrails and utility poles.    Specific accumulations included 4.5 inches in Kutztown (Berks County), 4.0 inches in Lower Macungie Township (Lehigh County), 3.8 inches in Palm (Montgomery County), 3.6 inches at the Lehigh Valley International Airport and Williams Township (Northampton County), 3.5 inches in Springtown (Bucks County), Bethlehem (Northampton County), Boyertown and Bechtelsville (Berks County), 3.4 inches in East Saylorsburg (Monroe County) 3.3 inches in Phoenixville (Chester County), 3.2 inches in Doylestown (Bucks County), 3.0 inches in East Nantmeal Township (Chester County) and Lehighton (Carbon County), 1.5 inches in East Stroudsburg (Monroe County), 1.1 inches in West Chester (Chester County) and 1.0 inch in Neshaminy (Bucks County) and Conshohocken (Montgomery County).The low pressure system responsible for the wintry mix moved from the Oklahoma/Texas border on the morning of the 17th, into the Tennessee Valley the morning of the 18th and east of Long Island during the late afternoon of the 18th. The low pressure system combined with a cold front that moved from the Upper Mississippi Valley the morning of the 17th east through Pennsylvania during the afternoon of the 18th to wring moisture from the atmosphere onto the region.

Winter Weather in MONROE, PENNSYLVANIA
From 17-JAN-04 19:00:00 to 18-JAN-04 14:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Weather in MONTGOMERY, PENNSYLVANIA
From 17-JAN-04 19:00:00 to 18-JAN-04 16:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Weather in NORTHAMPTON, PENNSYLVANIA
From 17-JAN-04 19:00:00 to 18-JAN-04 15:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Weather in BERKS, PENNSYLVANIA
From 17-JAN-04 18:00:00 to 18-JAN-04 15:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Weather in BUCKS, PENNSYLVANIA
From 17-JAN-04 20:00:00 to 18-JAN-04 17:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Weather in CARBON, PENNSYLVANIA
From 17-JAN-04 19:00:00 to 18-JAN-04 13:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Weather in CHESTER, PENNSYLVANIA
From 17-JAN-04 19:00:00 to 18-JAN-04 16:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Weather in LEHIGH, PENNSYLVANIA
From 17-JAN-04 19:00:00 to 18-JAN-04 15:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC