Complicated weekend storm for Montreal and Ottawa

Another weekend, another messy winter storm for southern Quebec. A special weather statement is in effect for Montreal, for a mix of rain, wet snow and freezing rain through Sunday.

This has not been an easy winter to predict for both professional and amateur meteorologists alike. For instance, I was convinced that once January turned colder, that frigid air was with us well into February. Now here we sit Friday afternoon with the temperature at 1C (34F), the third consecutive day above freezing. It seems that cold air this winter has been fleeting at best, the bulk of the arctic air trapped across northern Canada, with just an intrusion or two into the western provinces.

For this reason, the storm systems have been extremely challenging to forecast, especially the precipitation type. This weekends winter storm is no different. Right up to this mornings computer model runs, the various forecast scenarios have been all over the place, this with less than 24 hours to go before the storms arrival. So here goes my best effort at breaking down the weekend weather.

Precipitation should change to snow late Saturday, with 10cm expected in metro Montreal by Sunday morning. (AccuWeather.com)

A complex area of low pressure will move across the central Great Lakes and just south of Montreal on Sunday, while a second low develops off the southern New England coast. Clouds will increase early Saturday morning, followed by some scattered light rain or freezing rain into the early evening hours. Temperatures will be marginal at best for frozen precipitation in Montreal, with the mercury close to 2C (36F). Overnight Saturday into Sunday, slightly colder air should be pulled into the region, with precipitation becoming predominately snow for Montreal and points north and west including Ottawa. Precipitation may remain liquid south of Montreal. On Sunday, look for a mix or wet snow and perhaps some rain. If the precipitation remains as snow, most areas will receive between 10 and 20cm. Any region that mixes in with rain or freezing rain, will see less accumulation.

The temperatures will remain either side of 0C (32F), from late Saturday into Sunday. By no means is this forecast set in stone. I expect we will see fluctuations in the type and quantity of precipitation forecast. A change in the temperature of a degree or two either way, or any alteration in the storms track, will result in very different weather here in the St. Lawrence Valley. Skies will clear out on Monday, with temperatures remaining above normal.