Fall 1976 was cold throughout America. Winter 1976-1977 was one of the coldest on record. Why it was cold. It has to do with Pacific-North America (PNA)
The cause of the unrelenting cold was a persistent atmospheric circulation pattern that established itself in early autumn 1976 and remained remarkably unchanged until late February 1977. The Aleutian Low, a semi-permanent feature of the annual circulation map, was especially deep and large that winter, spreading to cover most of the North Pacific by January. It maintained a stronger-than-normal upper-level ridge over western North America and a deeper-than-normal upper-level trough over eastern regions of the continent. A large blocking high pressure cell pushed the polar vortex far south into southern Canada, and this extremely cold air streamed out from the arctic across the eastern and central United States and southeastern Canada.
http://www.islandnet.com/~see/weather/a ... m02jan.htm
