The day-10 temperature anomaly forecast at 10 MB reveals a stratospheric warming episode over northwestern North America. The warming causes an arctic air mass to develop over Northwest Russia in the 6-10-day period. On day-15, the stratospheric warming is widening and, frankly, looks scary as widespread arctic air is normally produced by this signature. However, for now, the “most likely” scenario is arctic air moves east across Eurasia and is shifting southeastward toward China much like the outbreak in December.

Forecast models generally doubt a major arctic outbreak into the U.S. ahead. The coldest possibility is presented by the mega-cluster ensemble rating widespread cold in 15 days (Feb. 20) at 23% risk. The most likely scenario, given the evidence available, is sharp cold risk to areas with snow cover near the U.S./Canada border east of the Continental Divide. Cold weather traveling south of where snow cover is located is brief and will moderate.

Persistent upper trough across Northwest Eurasia during winter 2023-24 shifts to Central Europe. Gradually, Northern Europe chill shifts farther south. The upper trough triggers a significant storm track across Southern Europe through the Black Sea region with increasing risk of snow.

Stratospheric warming returns to Siberia in 12+ days. Risk of arctic air generating in Eurasia returns. If so, where does the air mass travel? The midday (Jan. 31) suggests the air mass evolves and may want to travel cross-polar into North America. The risk is still low but increasing for potential important cold in the U.S. Feb. 18-24.