United States

Snow headed for Prairies then southern Ontario

March 13, 2013; 4:18 PM

A fairly active weather pattern will be in place over the next seven to 10 days across Canada and the northern U.S. as a strong blocking high builds toward Greenland, forcing very cold air to spread from northwest Canada to eastern Canada/northeast U.S. At the same time, unseasonably warm air will cover the western and southern half of the U.S. Where these air masses clash, there will be a series of storms running southeastward along the frontal boundary with snow to the north of the storm tracks.

The storm I will be focusing on today is still out over the northeast Pacific. This storm will bring more heavy rain to coastal BC tonight and Thursday morning. The energy from this storm will transfer across the Rockies later Thursday and then dive southeastward into the northern U.S. Plains Thursday night and continue east-southeast after that.

It will be quite mild south of the storm center track, while Arctic air will try to press in to the north of the storm track across the southern Prairies going into Friday.

Latest computer models have trended slightly south with the storm track, which makes sense with such strong blocking to the north.

Like most of these storms coming in from the northwest, there will be limited moisture, but I do think there will be a narrow band of heavier snow with this.

Clearly, due to elevation and upslope winds, the heaviest snow will fall across the Canadian Rockies with local amounts of 30 cm from Thursday to early Friday.

At this point, I think the band of heavier snowfall does run close to Edmonton, Saskatoon and Regina Thursday night into Friday morning, but then south of Winnipeg. In general, expect a solid 5-10 cm with local amounts of 15 cm.

The storm will then track toward Pennsylvania by Saturday, putting parts of Ontario under the steadier snow Friday night into early Saturday. At this point, it looks like a general 4-8 cm for southern Ontario, but I will have more detail on that tomorrow. If anything, we may have to adjust the below map a little farther south.

Since the snow will be coming in at night it does look like roads will get slippery into Saturday morning.

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The overall pattern over the next week or two does favor cold over warm for much of southern Canada, no doubt about that. A strong block over northeast Canada will continue to force waves of cold much farther south and east compared to normal.

The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com