The stratospheric warming event of mid-November to mid-December is dissipating. The warming event took place on the American side of the North Pole and spawned a polar vortex in North America causing the early meteorological winter 2025-26 arctic outbreak across the eastern states. Forecast models indicate the cold stratosphere across Eurasia expands cross-polar into North America later this month.

During the past week, the Nino34 and Nino3 sea surface temperature anomaly (SSTA) regions across the east-central and east equatorial Pacific Ocean cooled to the second strongest level of the weak late 2026 La Nina episode. The central equatorial Pacific and off the northwest coast of South America are near normal. Of interest is the appearance of a Kelvin Wave shifting east of the Dateline during early December.

The intense Pacific “atmospheric river” storm track across California to the Great Basin is releasing mild maritime air eastward of the Continental Divide extending anomalous warmth to the Atlantic Seaboard. Canada is very cold, and the attendant chill should extend southward across snow cover. New York and New England are at risk of "sneaky cold" late December.

Lack of snow cover is helping to propel a mild climate across Europe. However, a colder change may be on the way in the extended range. Stratospheric warming propelling an arctic air mass in Canada and into the East U.S. during early December shifts westward to Asia during the next 2-3 weeks. The emerging stratospheric warming over Asia will cause a cold air mass to initiate across Northern Asia into early next week.