THE VERMONT WEATHER BOOK by David Ludlum (Vermont Historical Society, 1996)
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In November the main jet stream, after crossing the middle of the Pacific Ocean near 40°N, enters the continent over Vancouver Island, and then races east in undulating fashion with a sweeping curve into the Midwest as far south as the Ohio Valley. Trending northeast, it carries over central New England where it is a principal agent in creating the storminess and heavy precipitation that characterizes the eleventh month in Vermont.
Several new features of the winter storm tracks make their appearance this month. Low-pressure systems generate over the eastern slopes of the Rocky Mountains, mainly in Alberta and Colorado, and converge over the Great Lakes to create a zone of maximum storminess there.
The St. Lawrence Valley serves as the pathway to the northeast for low-pressure systems, which cause Vermont’s weather to experience quick changes as the warm and cold fronts sweep through. An additional storm track from the Gulf of Mexico sends cyclonic disturbances northeast with increasing frequency along either flank of the Appalachian Mountains, both paths ultimately affecting Green Mountain weather.
The winter path of polar anticyclones from northwest Canada becomes well established during November. Moving southeast over the western prairies and northern plains, the polar anticyclones pass west and south of the Great Lakes. Later they often stall over the central Appalachians and give rise to a West Virginia high situation that blocks the normal movement of storms across the country and brings on a spell of settled conditions over the Northeast.
The downward trend in temperature accelerates from October to November, the decrease ranging from 12.6 degrees at Newport in the northeast to 11.5 degrees at Dorset in the southwest. The absolute difference of monthly means between north and south increases to about four degrees: Newport 34.3° and Vernon 38.5°. The extremes over recent years run from 81° at Bellows Falls in 1950 to -19° at White River Junction in 1938. The range at Burlington has been from 75° to -3°.
Precipitation increases from October to November by moderate amounts in the northeast and west, but in the southeast section November leads all other months for wetness, having an average of 4.23 inches, or 1.02 inches more than October. The larger amount can be attributed to the greater frequency of storms, especially along the Atlantic seaboard where northeast coastal disturbances develop and sometimes attain unusual severity. Vermont’s greatest rainstorm, resulting in the tragic Flood of 1927, was a November product of the subtropical Atlantic Ocean. On the average the drier northwest has a November catch of 2.80 inches at Burlington, in contrast to the wetter south where Searsburg Station has 5.18 inches, a ratio of almost one to two.
Thanksgiving is a holiday anticipated and enjoyed by all, but often it brings far from ideal conditions for going “over the river and through the woods to grandmother’s house.” The fourth Thursday may fall on any day from the 22nd to the 28th. A study of weather conditions at Burlington reveals that temperatures during this period have ranged from 69° in 1953 to -3° in 1938. On 53 percent of Thanksgiving Days, no measurable precipitation has fallen, and no heavy falls of rain over 1 inch have been recorded in the past century. Snow fell on 73 percent of the precipitation days. The biggest Thanksgiving Day snowstorm occurred in 1971 when as much as 20 inches fell atop Mt. Mansfield and 16.3 inches at Newport. The snowfall covered all the state, with Vernon in the southeast reporting an even 12 inches.
