Potential for significant pattern change starting around the second week of December
November 28, 2017; 10:58 AM
Pattern this week
Likely pattern Dec. 4-7
Potential pattern after Dec. 7
Below is my latest interpretation of the latest European model weekly output. A building west coast ridge combined with the Arctic and North Atlantic oscillations going negative would strongly support the idea of a turn to much colder weather after Dec. 8 in the eastern half of North America. The big question that is still unanswered is where will the east coast storm track setup. The latest European appears to say that most of the storms will track far enough offshore for little impact in the Northeast U.S./eastern Canada and the interior Maritimes. However, just a slight shift in the trough and ridge axis can easily change this, resulting in a stormier pattern farther west with the opportunities for snow. One thing that I am fairly confident in is that this pattern should support at least a couple rounds of significant lake-effect snow downwind of the Great Lakes.
Building West Coast ridge after Dec. 5 should also lead to a much drier pattern in that region.
**Keep in mind, the maps below are an average of that particular week. So a week that starts out mild and ends up cold may still show up as mild or neutral in some cases.
The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com