Multifaceted winter storm to target southern Quebec

Another spectacular February sunset in Montreal, the calm before the storm.

A special weather statement is in effect for the entire region as a winter storm develops over the next 24 to 48 hours.

A rather complicated winter storm featuring rain, flooding, strong winds, record high temperatures and eventually a flash freeze with heavy snow, will impact southern Quebec beginning Thursday. Much warmer air is streaming into the St. Lawrence Valley early Wednesday morning, allowing temperatures to finally rise after a 72 hour period of arctic air. The high Wednesday will be 4C (39F) under cloudy skies after low temperatures in the minus teens in Montreal.

Developing low pressure is expected to move northeast from the southern US along a cold front that is expected to move into our region late Thursday. The storm will pass just south of Montreal during the wee hours Friday morning. In advance of the cold front, a strong push of very warm air will result in record breaking high temperatures for many of us in southern Ontario and Quebec. The forecast high for Montreal on Thursday is 8C (46F), the record for the date is 6.8C (44F) set in 2011. 

Despite the record warmth forecast for Thursday, there may be a fresh 10 to 15cm of snow on the ground in Montreal by Friday morning. (AccuWeather.com)

Rain is forecast to develop on Thursday, with as much as 15 to 25mm for many locations. The heavy rain, mild temperatures and melting snow will lead to some localized flooding concerns. Strong southerly winds will develop on Wednesday afternoon, gusting up to 50km/h in Montreal, and 90km/h in the Richelieu Valley.

By late in the day Thursday, cold air will begin to filter into eastern Ontario and southern Quebec changing the rain to snow, with a period freezing rain possible for many locations including Ottawa and Montreal. Winds will become strong once again, backing to the northwest 30 to 50km/h. Temperatures will rapidly fall below freezing, down to -10C (14F) by Friday morning. The snow may be heavy at times with 10-15cm possible for many locations. Strong winds will cause blowing snow, and rapidly falling temperatures will turn any standing water to ice.

All this will be highly dependant on the track of the low pressure area and the timing of the cold front. The forecast is subject to change and as I said is quite complicated with plenty of moving parts. Weather warnings will likely be needed for several regions.