A historic ridge is peaking over the West Coast of North America, but you wouldn't know it. The late-fall impacts are more muted, as the amount of solar energy available is a fraction of what is obtainable in June.
The satellite imagery is eerie from June 2021. It was anything but calm on the surface. The heat increased day after day, and that vicious feedback effect produced deadly consequences.
This November and June 2021 share a similar anomaly in the upper atmosphere. If you compare both ridges using a standardized anomaly, the heat dome peaked at over four standard deviations from normal.
November 2022, the height of the ridge -- an elongated region of high pressure in the upper atmosphere -- peaks at over four standard deviations across the Yukon this week.
The impacts are far from extreme because we're working with around six hours of daylight under the northern ridge, but the surface temperature anomalies are still troubling. Northern Alaska and the Arctic Ocean surge above the freezing mark, touching 20°C above normal.
Farther down the coast, the anomalies were above the ground. It's called an inversion, and 1500 metres above sea level, temperatures spilled into the low teens while the lower elevations faced low clouds and fog.
Low clouds are locked in like cement in these setups for interior valleys, blocking the sun from warming up the valley bottoms. It's one of those unusual paradoxes you get in the fall and winter. As the strength of the ridge increases and temperatures aloft warm, the result is chilly and even below-seasonal temperatures at the surface.