Thursday, March 03, 2016

The mystery of the missing blizzard in Montreal

Near-blizzard conditions were observed along the St. Lawrence River north and east of Montreal. A section of Highway 20 east of Quebec City was closed from Levis to La Pocatier, most of Wednesday morning. (Transport Quebec)
That was not much of a storm, at least here in Montreal. A swath of heavy snow did impact regions from central Ontario, through the Ottawa Valley, and northeast towards Quebec City. Along that path, between 20 and 30cm of snow fell. South of there, the snow trailed off quickly. Here in Montreal, warmer air aloft turned the snow to ice pellets. Trudeau Airport measured a messy mix of close to 10cm, along with strong winds up to 75km/h.

Other parts of southern Quebec, Ontario, Vermont and New York had more freezing rain than snow. (Black Forks Towing Photo)
So what happened? In short, the system traveled about 100km further northwest than originally indicated by several forecast models. This introduced a small zone of warmer air above the surface, which cut off the snow here in Montreal and produced freezing rain and sleet. Environment Canada is not alone in the assessment of this storm, several other weather agencies both public and private, on both sides of the border, called this one wrong. But, forecasting winter storms is one of the most challenging things a meteorologist has to do, especially here in southern Quebec. A change in trajectory of just a few kilometres can mean the difference between a major impact winter storm and a complete miss. As we have seen this winter, just a few kilometres of geography can have a wide range of temperatures and precipitation types.

Where the Quebec Weather Centre made a big mistake on this particular system was upgrading its status to a blizzard. A blizzard is the worst type of winter storm, very few achieve this status, and this system was never that strong from the onset. At best, marginal blizzard conditions might have occurred for an hour or two in the dead of night, and a winter storm warning would have covered that scenario just fine. All the neighbouring weather offices chose to use that type of warning to cover this storm. I have been writing and following weather in the St. Lawrence Valley since I was 12, which would date back to 1978. In all those years, I don't recall Environment Canada here in Quebec issuing a blizzard warning regarding any potential snowstorm.

In any event, milder weather is on the horizon and Spring is close at hand. If you believe the extended forecast, it looks like an early, very warm spring, starting as soon as next week.

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