Saturday, December 21, 2013

Major Winter Storm for Montreal & St. Lawrence Valley

Ice and snow slowed the morning commute to a crawl in Montreal on Friday. More of the same today and Sunday as the roads are in terrible shape. (ValleyWX)
A winter storm warning has been posted for metro Montreal and points north with a freezing rain warning for points south to the US border and along the entire St. Lawrence Valley as well as southern Ontario including Toronto. An Ice Storm Warning is now in effect for the valley locations of northern Vermont and New York including Plattsburgh. This morning freezing rain and sleet (ice pellets) are falling here on L'Ile Perrot with a cold temperature of -8C (18F) Meanwhile not too far south temperatures are surging to near 50F across the Green Mountains of southern Vermont.

Lots of moisture will be surging north into an arctic frontal boundary that lies across Ontario and into central New York and Vermont. South of this front it is spring like with rain. North of the front very much like the first day of winter with windy and cold conditions and lots of wintry precipitation. Yesterday Montreal received nearly 15cm (6") of snow with another 5cm (2") of sleet and snow overnight. That brings our totals for the last week to over 50cm (20 inches). We will add to that today with a very tricky and complicated forecast. I will try to briefly make some sense of it below.

The freezing rain and sleet falling this morning across Montreal will become light and scattered today as we await the next wave of moisture tonight. The moisture will ride north with very warm air overriding the cold air here on the valley floor. The result will be a mix of snow, sleet and freezing rain, heavy at times, from Montreal to Toronto and south. The heaviest freezing rain will fall along the 401 from Toronto to Kingston and then south along the US border. The NWS in Burlington is hinting that this may be the biggest ice storm since 1998. There may even be a rumble of thunder with the heaviest precipitation overnight. Precipitation will taper off slowly by Sunday afternoon. There is a real risk for power outages and travel problems late tonight. You should cancel any travel plans for Sunday and wait until Monday. Precipitation will be mostly in the form of snow north of Montreal and into Ottawa. As much as 20cm of snow may fall. Here in Montreal it will be windy as well gusting out of the cold northeast to 70km/h tonight and early Sunday.

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