Ag Weather Forum

The weather pattern across North America has taken on what meteorologists call a positive Pacific North America pattern or positive PNA during the recent week. This means that an upper level ridge has developed across the coast of Western Canada, while a trough lies across central and Eastern Canada much of the time.

The result of a pattern like this is to block of any modifying influence of the mild Pacific to interior Western Canada and points east. With a now well-established snow cover across much of Canada and with long nights, temperatures can plummet quickly and have as we have witnessed during the last few days.

Arctic high pressure at the surface across northwest Canada sends surges of arctic air southeastward through the Prairies and then east into central Canada and southward across the Midwest of the U.S. This pattern will be in place for the next week or two but for the Canadian Prairies there may be enough of an eastward nudge to the pattern during next week to allow for some temperature moderation, at least for western areas of the Prairies.

Periods of bitter cold weather will continue into Saturday before down-sloping winds allow readings to come back up to more-normal temperature levels from Sunday into Tuesday. Manitoba could see temperatures stay pretty cold with a couple more bubbles of arctic high likely to progress southeastward from the Northwest Territories.

Some of our longer range models are implying that by the middle of December the pattern may retrograde, or move backward, again allowing for better delivery of arctic air throughout the Prairies.

One piece of good news for those who don't want snow is that the pattern during the next week or so should produce only limited amounts of snow, since we'll be developing more of a westerly surface flow. Westerly winds are usually drier winds for Western Canada to the east of the Rockies. Most of the clipper low pressure areas should be tracking north of the Prairies, possibly bringing Manitoba a better chance of some light snow once in a while.

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

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