Strong upper-atmosphere high pressure ridges in the Pacific Ocean and the eastern part of North America continue to influence the weather pattern over the Canadian Prairies. There are hints that a strong Pacific ridge might want to bridge across and merge with a much weaker ridge located over the North Pole. The implications of this merging would be to develop a high-latitude blocking high pressure pattern over western North America. Should this occur, the most likely outcome would be to force the polar trough currently located northwest of Hudson Bay to the south. This would lead to turn to much colder weather in Western and probably Central Canada.
The European forecast model shows a significantly stronger ridge in the Pacific, and a somewhat deeper or more wide-ranging trough in northern Canada. We also note on the European model that the trough line is further to the east. The reason for this is likely because of a weaker ridge over Eastern Canada. This weaker ridge allows for more movement of the southern portion of the trough, and lines it up more with the northern trough. This model is, therefore, hinting at a turn to colder weather in Western Canada sooner than what would be suggested on the U.S. model.
The U.S. model maintains a stronger ridge over Central and Eastern Canada than does the European model. Ridge development in the U.S. model depiction is forecast to remain strong enough to block eastward movement of the southwest Canada trough. This, in turn, maintains the southwest flow over the Canadian Prairies, and therefore is somewhat warmer-looking than the European model. Also on the U.S. model, both the Pacific ridge and the northern Canada trough are weaker. This depiction would also suggest less of a chance for significantly colder weather for the region compared with the European model.
The chance that the Pacific ridge would merge with the polar ridge is an interesting development, and one that would suggest a turn to early cold weather. However, in order for this to be included in a high-confidence forecast we would need to see a few more changes on these maps and better model agreement. We would first look for a better link between the ridge centers in the Pacific and in the Arctic. We would also like to see the models agree in the strength of the Pacific ridge and the weakening of the eastern North American ridge. However, the potential for these features to bring a colder pattern to Western Canada is an item that certainly warrants attention.
Joel Burgio can be reached at firstname.lastname@example.org
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