A historic warm December 2023 featuring monthly temperature departures from normal of +8F to +14F across the North-central U.S. and >4F for almost the entire northern half of the U.S. are about to fade. North Atlantic oscillation (NAO) is getting ready to shift from values >+2.0 in Mid-December to an average of about -1.5 for January 5-17, 2024. Consequently, a blocking high pressure area over Greenland forces a strong longwave trough across Central Canada to the Southwest U.S. causing a snowy/colder January regime ahead.

Energy markets grapple with risk of arctic air intrusion to the U.S. in 10+ days due to presence of a stratospheric warming event emerging over Eurasia over the next week or so, shifting into northwest North America in 10 days, and likely collapsing in 15 days (according to NOAA/CPC).

In summary, the combination of an eastward shifting MJO across the tropical Atlantic and stratospheric warming over Siberia to northwest North America increases the risk of a brief sneaky cold pattern in North America. Forecast models indicate a low risk but close monitoring for significant changes of the forecast in early January is warranted. Through 10 days, AI models do not see the cold air risk for the U.S.