Thursday, 20 February 2014

Freezing rain warning for Montreal

A major storm is taking shape over the central US plains today and is expected to lift northward towards the central Great Lakes. After a sunny, mild day here in Montreal clouds will be on the increase this evening. Expect precipitation in the form of a mix of snow and freezing rain to begin after about 8pm this evening and continue overnight. I believe we will see a quick change to plain rain here in Montreal and points south to the US border and beyond. However north and east of Montreal as well as in the Ottawa Valley the freezing rain may last into the Friday morning commute. There will be lots of water and ice around on Friday morning so allow yourself extra time. Total precipitation will be significant with this storm with between 25-50mm (1-2 inches) expected across southern Ontario, southwest Quebec and northern New England. For this reason Environment Canada has posted a freezing rain warning for Montreal and the Ottawa Valley, with heavy rainfall warnings posted for southern and eastern Ontario. Temperatures will rise to 4C today and drop just below freezing to -1C tonight in Montreal. It will be 4C on Friday in the rain. By late Friday afternoon a very strong cold front will sweep the region with a few heavier showers and perhaps a rumble of thunder. Winds will be gusty on Friday out of the southwest up to 70km/h possible ahead of the cold front.

My concern as always with an elongated warm front, is just how quickly we can dislodge the cold air at the surface of the St. Lawrence Valley. I believe it will be fast this time with a quick transition over to plain rain, but you just never know, each front behaves so differently once it interacts with the valley. Keep in mind that we have a very cold surface and even when the temperatures go above freezing there will still be lots of ice around under the puddles.

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