Warm air covered much of the country during early November 1975 as a big upper-level ridge covered much of the country.
Big-time Warmth Ahead of the Big Storm
By Karl Bohnak
Tuesday, November 03, 2009 at 4:36 p.m.
Rarely, if ever, does Upper Michigan experience November warmth of the magnitude felt in 1975. The thermometer flirted with 70 on several days during the first week of the month as a big, broad ridge of warm high pressure aloft centered itself over the mid-continent (Image above). The unseasonable warmth spread out over a large share of the country. Afternoon highs approached 80 in a wide arc from the Montana plains through the Mid-Mississippi Valley to the Mid-Atlantic.
In the U.P., it went above 70 degrees on two consecutive days (Nov. 5-6) at Ironwood, while in Marquette the 70 degree high on the 6th was the latest such reading in the record books. From November 2-8, 1975, the mean temperature in Marquette was 17.3 degrees above normal.
By November 7, the ridge was shoved to the East Coast as Pacific energy began working from the West Coast into the Great Plains. Colder air gradually seeped into the Rockies and spread eastward. At the same time, a strong disturbance shot southeastward out of the Gulf of Alaska toward the lower 48. It was this ripple in the flow that initiated Colorado low-pressure development late on the 8th. This low became the powerful storm that buffeted Lake Superior with storm-force winds leading to the unthinkable sinking of a modern Great Lakes freighter two days later.
