ECM and CFS V2 in Disagreement on 2nd Half of December in U.S.

Charts of the day: U.S. gas population weight HDD forecasts.

Discussion: The U.S. gas population weight HDD forecast trend remains slightly less cold for next week and Dec. 6-12. In the extended range, ECM indicates above normal U.S. heating demand regenerates while CFS V2 is somewhat warmer.

Medium-range 6-10 Day Forecast Valid December 2-6, 2024 (24-hour change)

Discussion: The southern periphery of the eastern chill moderates late in the 6-10-day period. New cold is observed in Western Canada.

Medium-range 11-15 Day Forecast Valid December 7-11, 2024 (24-hour change)

Discussion: The Canadian forecast trend is colder except for far Western Canada. The colder Canadian air mass extends into the Northeast States most effectively late in the 11-15-day period. The remainder of the eastern half of the U.S. shifts warmer.

U.S. Medium-range Precipitation Forecast

Discussion: The medium-range precipitation outlook is consistent as most of the U.S. is dry while Western Canada is snowy (possibly leading to a colder than indicated forecast) and wet weather affects Texas.

Days 16-20 Extended range Temperature Forecast valid December 12-16, 2024

Discussion: ECM stays cold in the East while CFS V2 is warm. The GFS ENS splits the difference with near normal in the East while the West is warm.