December 2021 Second Warmest This Century in the U.S.

Fig. 1-2: NAM (today) and ECM (THU/FRI) 24-hour snowfall forecasts.

Fig. 3: GFS 120-hour precipitation forecast for the Northwest U.S.

Storms this week: Focus is on East U.S. snowstorms and Northwest excessive precipitation. Winter Storm Warning for 6-12 in. of snow is in effect today centered on Virginia also affecting D.C. and Maryland to Delaware (Fig. 1). A second storm is forecast by ECM into the Interior Northeast THU/FRI (Fig. 2). Over one foot of snow is possible northwest of New York City with the second storm. The GFS indicates the late week snowstorm is farther south…over the Mid-Atlantic States similar to today. In the Northwest, another stormy week with several inches of rain near the coast and several feet of snow in mountain areas (Fig. 3). In the short-term a Freeze Warning is in effect this morning to 9-10AM across the west/north Gulf of Mexico coastal regions (Fig. 4). High wind today across the Southeast States. A plethora of Winter Storm warning/Advisory areas across the West including persistent Avalanche Warning(s) in Utah/Colorado. Freeze and Frost affects southern California near the coast.

Fig. 4: NOAA/NWS weather watch, warning and advisory areas for the U.S.

HDD forecasts: December 2021 produced 688 HDD which trails only 2015 (640) making the month the second warmest start to meteorological winter this century (Fig. 5). The current 15-day U.S. gas population weight HDD forecast shifts much warmer since yesterday (Fig. 6).

Fig. 5: The HDD anomaly observations (through December) and forecast through April compared to the last 3 years.

Fig. 6: U.S. gas population weight HDD forecasts by all models, their consensus, comparison to 24 hours ago and 10-year/30-year normal.