Ag Weather Forum
Doug Webster DTN Senior Ag Meteorologist

Thursday 12/06/12

Arctic Air has a Hold on the Prairies

For those living south of the Canadian border cold weather has been mostly hard to find during the past several weeks. Other than a few brief episodes of low temperatures, we have seen mild Pacific air dominate. The story is quite different across Western Canada. Arctic air has had a pretty tight grip on the region since late October and through November.

Temperatures across the Canadian Prairies during November averaged from 2 to 6 degrees C (4 to 10 degrees F) below normal as arctic high pressure remained in place from the Yukon southeastward to central Saskatchewan. A large blocking high pressure area in the upper levels across eastern Siberia is the likely cause for the cold. This pattern allows for a large surface high to develop across Alaska and northwest Canada.

It is well known that during winter high pressure brings light winds, and when light winds occur over snow cover and are combined with the very long nights, temperatures plummet. This arctic cold tends to slip southeastward along the front range of the Canadian Rockies and keeps the crop areas of the Prairies in the ice box.

Current forecast model extrapolations for the next week point to more cold weather from Alberta to Manitoba. Temperatures may fall to well below zero F (minus 18 C) at night and may struggle to get far above that mark during the day at times. Some good news is that there remains a decent snow cover across the region that should protect any winter grain crops from the extreme cold.

There remains the possibility that some further light to moderate snow accumulations could fall during the next week or two. Low pressure disturbances are moving along the boundary of arctic cold across the Prairies and Pacific air that will lie across the northwest U.S.

Precipitation totals during November were mostly a bit above normal, which will help in the long term, as eventually this snow cover will melt when spring arrives and add to the topsoil moisture.

The cold weather can help enhance snowfall across the Prairies. Arctic air is commonly overrun by warmer air to the west allowing for snowfall. Add to that the tendency for arctic air to move uphill against the Rockies creating upslope snows.

Longer-range computer forecasts for later December and January point to more cold weather for western and especially northwest Canada. Given the time of year, we might expect to see some extremely low temperatures, but with the protective snow cover the winter grain crops should be able to make it through the cold weather with minimal problems.

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

(CZ/SK)

Posted at 10:45AM CST 12/06/12 by Doug Webster
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