Monday, 8 December 2014

Atlantic Coast storm to impact southern Quebec

Just one computer model depicting a major storm near New York City by early Wednesday morning. This scenario produces heavy wet snow over the St. Lawrence Valley.

A rather complex weather scenario is setting up this week with the potential to dump heavy wet snow on the St. Lawrence Valley from Brockville to Quebec City. Cold high pressure is in place this morning with some of the chilliest readings so far this season. Temperatures range from -11 to -15C on the island of Montreal, but as cold as -18C north of the city. Look for sunshine with increasing clouds today and a cold high of -8C. Those clouds will thicken on Tuesday in response to low pressure organizing off the US eastern seaboard. This system will deepen into a major storm with strong winds and heavy precipitation for all of New England, New York eastern Ontario, Quebec and Atlantic Canada. It has been a difficult scenario for the computer models to handle, and lots of uncertainty remains as to the type and location of the heaviest precipitation. Right now it looks like mostly wet snow for eastern Ontario and a rain snow mix for southern Quebec with perhaps a prolonged period of freezing rain.

The initial push of moisture will arrive by late Tuesday, I am hopeful after the evening commute for Montreal. That will result in a few centimetres of wet snow with highs near 0C (32F). The snow will continue overnight into Wednesday morning with the possibility of over 10cm by Wednesday morning. I don't think Wednesday will be a good driving day in Montreal and Ottawa as well as the Quebec City to Brockville corridor. Heading south the same situation will prevail with 15-30cm (6-12 inches) of wet snow possible over northern Vermont and New York. Winds will become very strong out of the northeast in Montreal gusting in excess of 50km/h by late Tuesday. Looking ahead the system will be in no hurry to move away lingering along the coast near New York City and continuing to pump moisture into our region. Light snow or a wintry mix may last well into Thursday or Friday.

Warnings will likely be required for a portion of our region later today. I will post those as soon as they are available. Plan your week accordingly as travel will be rather difficult at times.

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