Arctic Air May Be Returning Later This Month

Discussion: The midday report begins with the ending of the 12Z GFS. In 384 hours (the morning of Feb. 25^th) the model indicates an arctic outbreak into the Midwest/East-central U.S. (Fig. 1). Morning temperatures dip to zero in St. Louis and Chicago on Feb. 25^th. The 12Z GFS 6-10-day forecast stays cold in the West, trends colder in Canada, and remains warm in the East (Fig. 2). In the 11-15-day period, arctic air is making a widespread appearance in Canada and some of that air moves into the U.S. (Fig. 3). The U.S. gas population weight HDD forecast at midday is not impressively colder for Feb. 17-23 as the cold ending of the 12Z GFS model run is just beyond that period (Table 1).

Fig. 1: The midday 12Z GFS brings arctic air into the U.S. in 16 days.

Fig. 2-3: The midday 12Z GFS medium-range temperature anomaly forecast for the U.S.

Table 1: The 12Z GFS U.S. gas population weight HDD forecast compared to 12 and 24 hours ago.