|A prolonged period of steady freezing rain is possible from Montreal to Cornwall on Tuesday.|
Winter Storm Watch: Eastern Ontario, St. Lawrence Valley of New York.
After the frigid cold this past weekend, most of southern Quebec, eastern Ontario and New England is looking at a winter storm for Tuesday. This has been a very tricky forecast from the start and continues to be that way. However, it is crunch time, so we need a forecast. It appears high pressure will remain in control today with moderating temperatures. The forecast high is -8C (18F), a vast improvement from the weekend, and from where we sit currently here on L'Ile Perrot, at -25C (-13F). Clouds will rapidly increase this evening, along with rising temperatures and the arrival of snow. Low pressure is forecast to strengthen rapidly as it moves from Virginia to northern New York on Tuesday. The low pressure center will pass very close to Montreal late Tuesday evening with precipitation tapering off afterwards. Precipitation will start as snow and rapidly change to freezing rain and eventually rain from south and east of Montreal into New England. Where the forecast becomes very hard is here in Montreal and points west.
The snow will start overnight tonight in our region. Snow will accumulate 10 to 20cm from Montreal north and west, with Ottawa receiving the most (close to 25cm). Current indications are that the St. Lawrence Valley from Montreal to Massena and Cornwall could see quite a prolonged period of steady freezing rain. As much as 10-15mm (up to 0.5 inches) of ice is quite possible along with gusty northeast winds. The question will be: How long will it take the warm air to scour out the cold air in the St. Lawrence Valley? That can take several hours, which could lead to significant ice accumulation on trees and power lines. Temperatures on Tuesday will eventually rise above freezing south and east of Montreal, but remain at the freezing point from off island suburbs to our west into Ontario. I will post an update on this storm later today. Plan for very poor travel on Tuesday and potential power outages.