Ag Weather Forum

Cold, arctic air has pushed through much of the country east of the Rockies during the last week. It started in the Canadian Prairies and Northern Plains, where temperatures below zero Fahrenheit were regular.

It then spread to the eastern half of the United States after Thanksgiving. While not as cold as it was farther northwest, temperatures in the Great Lakes have been low enough to produce massive amounts of lake-effect snow that haven't shut off in five days.

That has added up to more than 40 inches of snow on parts of the Chautauqua Ridge, the higher elevations between Cleveland and Buffalo, and more than 60 inches on parts of the Tug Hill Plateau east of Lake Ontario.

The arctic air has been giving those of us that live east of the Rockies a true sense of winter conditions, but it will not last much longer. Warmer air is set to move eastward this weekend, causing a wild swing in just a few days.

Until then, there is another burst of cold air that will spread through the eastern half of the country thanks to a clipper system moving through Canada Wednesday and Thursday. While most areas are seeing temperatures moderate ahead of the system across the Plains, Midwest and Southeast, another burst of cold, arctic air will follow quickly behind it. Another couple of days of arctic cold are in the forecast.

However, that will not last long. The reason for the cold intrusion was due to the upper-level setup. A ridge has taken over the western half of North America while a trough has set up in the eastern half. The ridge has poked far enough northward to tap into the arctic air near the North Pole.

Clipper systems coming down from Canada and into the eastern trough have reinforced this cold air during the last week or so and continue to do so. The upper-level pattern will be changing, starting this weekend. The western ridge will get strong enough to spread eastward this weekend, pushing the cold trough offshore and up toward Baffin Island in northeast Canada. The result will be a quick and dramatic warmup for those that have been in the arctic air.

A more chaotic pattern will result from this movement. As the ridge spreads out, it weakens, and another trough in the Pacific is likely to move through Western Canada and down into the Central U.S. early next week. Temperatures will take a dip again, but since this trough is sourcing air from the milder Pacific rather than the cold Arctic, the drop will not be as severe as what we saw during Thanksgiving. Temperatures are still likely to get below normal next week for a few days, but mostly across the southern tier of the country. The north will stay closer to normal and the shift back to warmer air is forecast to return a couple of days later.

The cold air should come with a storm system that may come in two pieces early-to-mid next week. Widespread precipitation will be possible, and models are favoring Texas into the Great Lakes with the heaviest precipitation as of now. Though the weather will be milder, temperatures will still be low enough for snow on the backside of the system or systems. Depending on the development of the low-pressure centers, it could cause some significant snowfall in parts of the Plains and Midwest.

Days later, the pattern shifts again with a trough settling into the West while a ridge builds in the East mid-December. That is reminiscent of the warm and wet pattern for the Central U.S. that was frequent in November. Western areas are forecast to turn colder, especially Western Canada, and we could set up the same series of events we saw at the end of November into early December for late December and early January. The extended versions of both the American and European models have suggestions that could be the case, though timing and intensity vary between the two.

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John Baranick can be reached at john.baranick@dtn.com

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