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Update on Potential Sunday night/Monday Storm

December 5, 2013; 3:44 PM ET

Brief update on the potential winter storm for eastern Canada during the Sunday night/Monday period. I will post the latest long range update later this evening after it is released.

The mix area for eastern Canada assumes accumulating snow followed by a mix of precipitation and perhaps ending as some rain or drizzle.

1. This will not be a strong, wound up storm, but more of what we call a large, warm advection event as moist, mild air from the Gulf of Mexico lifts northward and gets lifted over the cold air mass in front of it. As the air gets lifted, it condenses out as clouds then steady, widespread precipitation.

2. The primary storm will likely track up into the Great Lakes, which normally leads to a quick changeover from snow to rain over southern Ontario, but with a strong, Arctic high in the way the cold air will hold out, leading to an extended period of snow and mixed precipitation from southern Ontario through southern Quebec and into New Brunswick. A weak coastal storm could also form.

3. Main area of snow will move into Ontario Sunday night then Quebec/New Brunswick early Monday.

4. Based on what I am seeing now, I think as much as two-thirds of the precipitation from the GTA through Montreal during this event is frozen, then as the warmer air moves in it turns over to a lighter freezing rain or plain rain before ending.

5. Overall, this looks like a general 8-15 cm event for a large portion of eastern Canada before any changeover with lower amounts over extreme southern Ontario. A high percentage of this accumulation will likely occur in a 4-6 hour period.

6. Expect slow traffic and travel delays Monday morning, especially from the GTA on northeast into Quebec City.

I will have more details on this tomorrow.

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


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About This Blog

Brett Anderson
Brett Anderson covers both short-term and long-term weather and storm forecasts for Canada in this blog for