Highlight: The end of January northern hemisphere pattern.
Fig. 1: Mega-cluster ensemble “most likely” day 11-15 northern hemisphere temperature anomaly projection.
End of January 2021 northern hemisphere temperature anomaly look: Rather than using any single model the mega-cluster ensemble which accounts for all models projects “most likely” scenarios which are more reliable. The most recent mega-cluster ensemble projection of temperature anomalies for the northern hemisphere in the extended-range (days 11-15) indicates steady presence of the winter 2020-21 arctic air reservoir stretched across Russia (Fig. 1). Instead of pulsing southeastward into China as observed in late DEC/early JAN the air mass expands westward into Northern Europe. Meanwhile a narrow fetch of cross polar arctic air into North America convenes a new cold air mass across Southwest Canada. In the middle latitudes East Asia becomes the new warm spot. The persistence of a mild climate in North America fades to just East Canada to close January.
Latest gas population weight HDD forecast: Forecast model agreement is reasonable through next week. For Jan. 22-28 the GFS/GFS ENS take-off with cold HDD projections while other models are more temperate (Fig. 2). The consensus forecast for Jan. 22-28 is colder and now above the 30-year HDD climatology.
Fig. 2: Latest consensus of all operational model(s) gas population weight HDD forecasts for the U.S. into late January compared with 24 hours ago and the 10-year/30-year normal.
Short-term high impact weather: The “atmospheric river” across the North Pacific and into the Northwest U.S. early-to-middle week brought flooding rains to the Oregon/Washington coastal areas which has subsided and heavy mountain snow triggering avalanche warnings now in effect for parts of the Snake River Basin (mountain areas). The focus of this event now is to project hurricane force wind gusts for a large part of the north and central Great Plains today (Fig. 3). A new storm has formed in the Upper Midwest U.S. and rapidly lowering surface pressure spawns heavy snow coupled with high wind producing blizzard conditions today for southwest Minnesota southward to northwest Missouri. High wind from the north-northeast develops in the Los Angeles Basin area today spawning Red Flag Warnings.
Fig. 3: Latest NOAA/NWS weather watch, warning and advisory areas.
The GFS indicates potential for 4-12 in. of snow for the incoming snowstorm (Fig. 4). Given the high wind 2-3 foot drifts easily form. The storm is mostly rainfall in the Northeast late Friday night and Saturday (Fig. 5).
Fig. 4-5: GFS snowfall forecast for the Midwest and Saturday rainfall projection for New England.