Ag Weather Forum

Arctic Air Covers All but the Far West in Canada

Doug Webster
By  Doug Webster , DTN Senior Ag Meteorologist

The upper air pattern across North America has remained nearly unchanged since late January with a dominant trough across the eastern half of the continent held in place by anchoring ridges near the west coast of North America and a second strong ridge through the north-central Atlantic. Unlike last year, when we saw high latitude blocking produce the cold, this year the culprit is mid latitude blocking.

The only changes we see over time are periods when the trough de-amplifies while at other times it becomes highly amplified. This can almost be compared to a person inhaling and exhaling. During times of high amplification, arctic air is delivered southward to great distances. Typically, at the same time on the east side of the trough, a major storm ramps up and brings heavy snows, as New Englanders can attest.

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The Canadian Prairies have been on the receiving end of mostly the cold air and not so much of any snow of significance during the past month. The trough has been positioned so that arctic air has been very dominant across Saskatchewan and Manitoba and even parts of northeast Alberta.

For southwest Alberta we have seen some much milder weather at times as the West Coast ridge has allowed some Pacific air to ride across the mountains bringing readings as high as 15 Celsius in a few spots. There are also some parts of Alberta that have seen temperatures go up and down like a yo-yo during this period as arctic air and Pacific air get into a shoving match.

We see little change to this pattern for rest of February for the Prairies. Below- and at times well-below normal temperatures will persist for the eastern Prairies while Alberta sees readings highly variable at times. Snow threats still look mostly minor in nature but a few spots will continue to see a little snow every few days. Upslope snowfall should not be a long lasting product of this type of pattern.

With March just around the corner, our early take is that some change to the pattern is probably going to occur across North America beginning during the first week of March. The anchoring ridge near the West Coast is forecast to shift west for at least a little while and allow for increasing west or southwest flow aloft into Western Canada. The northern stream may remain in a fashion so that cold weather will only ease some across the central and eastern Prairies. This leads to the threat that an increase in precipitation in this new pattern could bring snow to the region for March along with temperatures still on the lower side of normal, but not so severe for eastern areas.

Doug Webster can be reached at doug.webster@dtn.com

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