Overnight, the U.S. gas population weight HDD forecast for Jan. 3-9 was revised colder by ALL models (except GFS). During Jan. 10-16, U.S. heating demand settles to the 30-year normal. The extended range HDD forecasts for the second half of January are near to below normal. Consequently, Jan. 3-9 is the coldest week of mid-winter.

In a new twist, ECM is forecasting a cold stratosphere across the polar region and eastern North America in the 11-15-day period. Elusive stratospheric warming shifts to Eurasia. Beneath the cold stratosphere, GFS indicates a mild ridge pattern in the East U.S. instead of an evolving polar vortex pattern as previously reported.

An expected cold change in January for North America is indicated by ECMWF which is vividly much colder in the extended range outlook. Most of the precipitation across the Northern U.S. is snow helping to enhance the cold.

The next cold temperature issue arises in the week-3 forecast when all “weeklies” models project an evolving upper trough in the East U.S. ECM continues with the strongest trough forecast. For the moment, arctic air is not anticipated with this upper trough.