Winter Weather in Pennsylvania, February 1 to 2, 1999

A low pressure system developed along the Gulf Coast the morning of February 1st. A broad southwest flow preceding the low brought warmer air aloft and precipitation into the Middle Atlantic States. A high pressure system that retreated from New Jersey into the Canadian Maritimes on the morning of the 2nd kept enough cold air near the ground for precipitation to start as freezing rain in sections of the Lehigh Valley and most of the Poconos the evening of the 1st. The low tracked northeast along the coastal plain and brought in milder air that raised temperatures above the freezing mark in all areas by the morning of the 2nd. Precipitation was light and intermittent during the evening of the first and became steadier after midnight. Temperatures rose above the freezing mark before the heavier rain moved north. About one to two tenths of an inch of ice accrued on exposed surfaces before the change to plain rain. Untreated roadways and walkways were treacherous.