Bitterly cold weekend followed by Monday snowstorm

Frigid air will move into Montreal on Friday, followed by the largest snowfall of the season so far on Monday, with 15-25cm anticipated for southern Quebec.

We have reached our high temperature for the day in Montreal at -7C (19F) early Friday morning. A frontal boundary that has been responsible for the clouds, freezing drizzle and light snow over the last 48 hours has finally drifted south into New York State. Much colder air is beginning to filter into southern Quebec on gusty northwest winds. Montreal will be sandwiched between a strong ocean storm that will bring Atlantic Canada heavy snow today and arctic high pressure over Ontario. The result will be a very strong push of arctic air on gusty northwest winds of 20-40km/h.

The temperature in Montreal on Friday will drop all day, reaching -18C (0F) by late afternoon. Wind speeds of up to 40km/h, will produce a biting windchill values in the minus 30s. The mercury will continue to fall, down to -25C (-13F) for lows by Saturday morning. Despite bright sunshine on Saturday, we will see very little upward movement on the temperature, possible reaching -20C for a high. Another cold night Saturday into Sunday at -22C (-8F), before slight moderation in temperatures on Sunday. The high will be near -10C (14F).

Heavy snow is forecast from the southern US into Quebec and Ontario on Sunday and Monday. (AccuWeather.com)

Major Snowstorm

Our attention will then turn to a developing winter storm along the US east coast. The energy that will become this storm is now located across the far western US and will dip into the southeastern part of the country. The system will then deepen as it lifts across the middle Atlantic and into New England by Monday. At this time, confidence is groining that we will see a swath of heavy snow across the St. Lawrence Valley, accompanied by strong northeast winds of 30 gusting to 70km/h at times. The combination of falling and blowing snow will create dangerous travel conditions on Monday across southern Quebec and eastern Ontario. At this time it appears a good 20 to 25cm is likely for Montreal, with 15 to 20cm across portions of the Ottawa Valley and 10 to 15cm in the Eastern Townships, where some sleet or freezing rain is possible as well. This is subject to change as the track of the storm becomes a little more clear over the next 24 hours. 

The snow will end Monday night followed by another surge of colder air for Tuesday. I anticipate weather watches and warnings will be required for this system and will provide updates throughout the weekend.