Thanksgiving weather history and the polar vortex

Thanksgiving is this Thursday, Nov. 27, and there is a good possibility of some rain and snow across the region. The holiday has been observed every fourth Thursday since 1942, so has been as early as Nov. 22 and as late as Nov. 28.

According to the U.S. National Archives and an article from www.cleveland.com, President George Washington declared Nov. 26, 1789, as a day of Thanksgiving, our first official Thanksgiving. From 1790 through 1862, there were various days scattered throughout the year declared as Thanksgiving by sitting presidents. Then, in 1863, President Lincoln declared Thanksgiving to be the last Thursday in November. This policy remained in effect until 1939 when President Roosevelt moved Thanksgiving to the second to the last Thursday of November. In late 1941, President Roosevelt and Congress established that the fourth Thursday of November would be Thanksgiving Day, a tradition that still exists today.

Looking back at the records for Coeur d’Alene, the most frigid Thanksgiving Day was Nov. 28, 1985, with a low temperature of -2 degrees. The afternoon high was only 22 degrees on that day. By contrast, the warmest Thanksgiving was Nov. 23, 2017, with a high of 60 degrees. The wettest Thanksgiving Day was back in 1960 on Nov. 24. A strong storm dumped 1.25 inches of precipitation in Coeur d’Alene on that date. In terms of snow, there was 3.7 inches measured Nov. 25, 2010, which was the snowiest Thanksgiving in Coeur d’Alene based on climatological records. Last year, our high was a chilly 36 degrees on Thanksgiving Day.

Thanksgiving in the United States is a time marked by family gatherings, busy airports and millions of people traveling across the country. However, the holiday season has also been shaped by dramatic and occasional major weather events.

One of the most dramatic storms around the Thanksgiving holiday was the Great Appalachian Storm of 1950, which struck from Nov. 22 to 27, and brought chaos to the eastern United States. The storm produced blizzard conditions from the Ohio Valley to New England and generated hurricane-force winds along the Atlantic Coast. Wind gusts of 83 miles per hour were reported at Albany, N.Y., resulting in extensive wind damage. Pittsburgh, Pa., received nearly 2 feet of snow, and mountainous areas of West Virginia saw more than 50 inches. The combination of extreme snow, wind and record-breaking cold contributed to hundreds of deaths and widespread damage.

One of the most memorable modern events that began Nov. 26, 2019, was the Thanksgiving Week Bomb Cyclone that affected much of the western U.S. The storm began as an exceptionally strong low-pressure system over the Pacific before rapidly intensifying as it came ashore in Oregon and California. Wind gusts of up to 70 to 100 miles per hour hit the coastal areas of Oregon and Northern California. Trees and power lines were either damaged or toppled and major highways were shut down. The Sierra Nevada received several feet of snow, closing mountain passes and stranding holiday travelers on Interstate 80. Farther inland, the system merged with colder air, producing blizzard conditions across Wyoming, Utah and Colorado. This event became one of the most disruptive Thanksgiving travel periods ever recorded in the West, but North Idaho was spared from the big event as only 0.1 inches of snow was measured in Coeur d’Alene.

Last year, there was another bomb cyclone that developed in front of the Thanksgiving holiday Nov. 18. The central pressure of the storm dropped to a record-tying 27.80 inches and dropped huge amounts of rain in Oregon and California. Wind gusts were nearly 80 miles per hour that led to widespread power outages. Over 200,000 were left without power in British Columbia, Canada. In Coeur d’Alene, 1.80 inches of rain fell from Nov. 20 through Nov. 24.

The last time we had measurable precipitation in Coeur d’Alene on Thanksgiving Day was back in 2021 on Nov. 25. With a high temperature of 43 degrees, there was 0.13 inches of moisture with 0.2 inches of snow.

In terms of our local weather conditions for December, it may be very winter-like across the Inland Northwest. Scientists and sophisticated weather forecast models are indicating that the “polar vortex” is expected to weaken and bring much colder and snowier conditions to parts of the northern U.S.

The polar vortex is a relatively large upper-level low pressure system consisting of large masses of cold, dense Arctic air that is located near the North Pole. There’s also a polar vortex at the South Pole. When the polar vortex is strong, the frigid cold air mass will often stay confined near the North Pole as the Jet stream increases in strength. But, when the vortex weakens and splits into two or more vortices, the cold air will often push southward.

With a potentially weakening polar vortex and a cooler La Niña sea-surface temperature pattern, the chances of snow in the lower elevations are higher. The long-range computer models are showing the chance for snow and colder temperatures in the Coeur d’Alene region over the Thanksgiving holiday weekend.

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Contact Randy Mann at [email protected].