12Z GFS Cold Bias Polar Region; Warm Bias Near U.S./Canada Border Past 30 Days

Highlight: Glance at 12Z GFS (midday) temperature bias; West is cooler at midday.

Fig. 1-2: The 12Z GFS temperature forecast bias during the past 30 days for the medium range.

Discussion: The midday 12Z GFS temperature bias for the 6-10-day period during the past 30 days is marginally warm in Southern Canada and the North-central U.S. but overall reasonable skill (Fig. 1). In the 11-15-day period, the polar region is much too cool while forecast bias near the U.S./Canada border has averaged too warm (Fig. 2). Today’s 12Z GFS medium-range forecast remains warm across the Central and East with primary change much cooler in the West during the 11-15-day period (Fig. 3-4). Kansas was much wetter based on the 12Z GFS.

Fig. 3-4: The midday 12Z GFS medium-range temperature anomaly forecast.

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