8:30AM Update, Tuesday, February 18: The snow has finally started in Montreal, arriving a couple of hours later than expected. Precipitation will become briefly moderate over the next few hours. A general 5 to locally 10cm is possible today in the city, with more north of Laval. Expect snow covered roads and reduced visibility, at least through the noon hour.
The snow will taper off to flurries or light drizzle later today as temperatures rise above freezing by the evening hours, up to 3C (38F). Winds will increase as the day moves along, gusting up to 60km/h and persisting into the overnight hours as well as Wednesday. A cold front will arrive before dawn Wednesday, producing a few snow showers, and dropping temperatures quickly back below freezing, down to -8C (17F) by the end of the day.
Previous Post: Snowfall Warning in effect for the Laurentians, Lachute, St Jerome and Quebec City
Winter Weather Advisory for the Ottawa and St. Lawrence Valley
The temperature roller coaster ride will persist this week, as it has all winter long. High pressure has been in control of our weather Monday, with abundant sunshine and seasonable temperatures. Clear skies will prevail into the evening hours, with temperatures dropping quickly after sunset to early lows of -13C (9F) in Montreal.
Clouds will be on the increase after midnight as developing low pressure moves from the southern plains into the Great Lakes. A warm front will lift north with the storm system, producing and area of light to moderate snowfall. The snow will move into Ontario overnight and unfortunately approach Montreal in time for the morning commute. Accumulations of 5 to 10cm are likely along the St. Lawrence River, with 15 to 20cm north of Laval and into the lower Laurentians. These regions are under snowfall warnings. A weather advisory is in effect for the St. Lawrence Valley in Ontario. No warnings have been posted for Montreal.
The timing of the snow will result in another slow morning commute in southern Quebec. Look for snow covered roads and reduced visibility. Precipitation should taper off in the the afternoon, as temperatures rise to the freezing point. Winds are expected to pick up as well on Tuesday afternoon, gusting between 40 and 60km/h in Montreal. The winds may even be stronger in the Richelieu Valley.
The temperature will briefly rise above freezing up to 3C (38F) during the evening hours, as the warm front lifts north of the the St. Lawrence Valley. A few isolated showers are possible, changing back to flurries as the temperatures drops once again below freezing by midnight, and down to -5C (23F) by Wednesday morning.