Friday, 2 January 2015

Winter storm to impact Montreal this weekend

Rare snow fell in the deserts of the southwestern US on New Years Eve as a strong storm system developed. This low will bring Ontario and Quebec the first winter storm of 2015. The photo above is from Lake Havasu City, Arizona, halfway between Las Vegas and Phoenix.
A rather cold air mass has settled into southern Quebec this morning after a few centimeters of snow on New Years Day. The snow was thanks to a rather vigorous lake effect snow band that drifted down the St. Lawrence Valley. That snow band was responsible for very poor travel conditions along the 401 from Montreal to Trenton. Numerous accidents, including a multi-vehicle pile up near Odessa, closed the highway for a period yesterday. Today there will be a break for Ontario and Quebec between two weather systems. Sunshine will prevail, but it is breezy and cold, currently at -10C (14F) in Montreal with a windchill of -16C (3F). We may gain a degree or two today but not much more than that.

Our attention then turns to developing low pressure area over the southwest US. This system brought snow and strong winds as well as freezing rain to portions of Arizona, Nevada, California, Texas and Oklahoma. It managed to snow in Las Vegas on New Years Eve! The storm will deepen as it moves towards the Great Lakes on Saturday with a wide swath of moisture moving into Ontario and Quebec. With cold air firmly in place in Montreal and Ottawa look for snow to start with perhaps as  much as 15cm (6 inches) from late Saturday into the wee hours Sunday morning. Much warmer air surging north on the east side of the storm will change precipitation over to freezing rain and eventually rain for a period on Sunday close to Ottawa, the St. Lawrence River and points south. Temperatures will be very cold Saturday, near -10C (14F) in Montreal but warm, according to Environment Canada, to 10C (50F) on Sunday. I think this is very generous given the history of the valley to hold onto cold air. It will rise above freezing Sunday and precipitation will change to rain, but I don't think we will see 10C (50F). Perhaps 5C (41F) may be more close to reality. But admittedly, I am no expert. Precipitation will taper to flurries on Sunday night as temperatures start to fall rapidly to -10C by Monday morning. Another factor with this storm will be strong winds as the storm continues to deepen over northern Quebec. Winds will increase Sunday up to 50 to 80km/h.

Next week look for the coldest air of the season to arrive by the middle of the week with temperatures down to -20C (-4F) or colder by Thursday morning. The cold air will be with us all week once this storm passes.

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