Friday, January 12, 2018

Rapid freeze and snowstorm to follow record high in Montreal

A powerful cold front will drop the temperature in Montreal from record values today to brutal cold by Sunday morning. Along with the cold will come heavy snow tonight and Saturday. (
Winter Storm Warning in effect for Montreal.

A major change in the weather will occur today as a powerful arctic front crosses the St. Lawrence Valley during the evening hours. Before then, we have a very warm and moist air mass over southern Quebec Friday morning. In fact several locations have already registered record high temperatures for the date. Saint Anicet reached 14C (56F) in the wee hours this morning, a remarkably warm temperature for January 12, and the warmest in the country. Montreal's Trudeau Airport is at 6.3C (44F), also a record for the date, surpassing the 5.3C set in 1986.

In addition to the mild weather, we have an area of heavy rain about to move into southern Quebec. A decent amount is forecast today, 15-20mm, creating the potential for some flooding. The rain is in advance of a sharp arctic boundary that will chase the warm air back to the south. The front will arrive in Montreal close to the evening commute, changing the rain to freezing rain and sleet. The temperature swing will be rapid and brutal, dropping from 7C (45F) in Montreal, down to -5C (23F) in just a few hours. A flash freeze is expected, with roads rapidly icing late in the day. The freezing rain should change to snow after 8pm in Montreal. Low pressure is forecast to move along the cold front tonight and Saturday, increasing the coverage of snow in Montreal. The snow will be heavy at times, especially Saturday morning. Accumulations of 15-25cm (6-10 inches) are expected. Gusty northwest winds behind the front tonight and Saturday will produce areas of blowing and drifting snow. The temperature will continue to fall on Saturday, down to a low of -22C (-8F) by Sunday morning. That represents nearly a 30 degree drop in temperatures from this morning.

Widespread weather warnings are in effect today from Ontario across Quebec, into Atlantic Canada and south into New England and New York. If you can, postpone any unnecessary travel from Friday evening thought Saturday afternoon.

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