Temporal and Spatial Variations of Freezing Rain in the Contiguous United States: 1948–2000

Abstract A new freezing-rain-days database was used to define the spatial and temporal distributions of freezing-rain days across the contiguous United States. The database contained 988 stations, spanning the period 1948–2000. Areas averaging one or more days of freezing rain annually included most of the eastern half of the United States and the Pacific Northwest. The national maximum is in portions of New York and Pennsylvania, a result of several weather conditions conducive to freezing rain. Other maxima included an east–west zone across the Midwest, an area along the eastern Appalachians, and the Pacific Northwest. The latter two maxima have high frequencies as a result of the mountains, which trap low-level cold air with warm air moving above, resulting in freezing rain. National maximum annual values during 1948–2000 were 3–5 times as great as annual averages, but the two patterns were similar. Average patterns for three discrete 17-yr periods between 1948 and 2000 were very similar, but the magni...