Stormy weather week ahead for the St. Lawrence Valley

Between 10 and 20cm of snow fell across the Montreal region Saturday night and early Sunday morning as the first widespread storm of the season moved across southern Québec. After a breezy, cold Monday, more snow, freezing rain and rain is on the way for the balance of the work week.

Expect difficult driving conditions at times this week, with a wide variety of precipitation and highly changeable temperatures across the region.

We can expect a brief break on Monday between the 10 and 20cm of snow that fell over the weekend and our next storm system rapidly on the horizon. It will be a very stormy week here in southern Quebec. The temperature roller coaster will persist as warm and cold air continues to battle over our region. After a cold, windy day Monday, with a high of -5C (23F), temperatures will rise on Tuesday, well-above freezing to 4C (39F).

Before then however, we can expect a burst of moderate snow right around the evening commute Monday, as a warm front lifts northeast across the region. The snow will certainly have an impact on the rush hour drive in Montreal, with as much as 5cm of snow this evening. As temperatures rise overnight, the snow will mix with and change to freezing rain in the St. Lawrence Valley, with a couple of millimetres of ice accretion possible. The freezing rain will taper off to showers Tuesday morning. Expect icy roads for the Tuesday morning commute.

Streets were snow covered across the Montreal region in the pre-dawn hours Sunday morning, but quick work by Transport Quebec and contractors, as well as milder temperatures Sunday, quickly melted the snow from most roads.

On Wednesday, a more impactful storm system is forecast to develop along the eastern seaboard and deepen rapidly as it moves north across New England and into Quebec. Heavy rain is forecast, with as much as 25mm for many locations in southern Quebec including Montreal. Temperatures will be very mild with the system, up to 5C (41F), so expect lots of melting and ponding of water. Some minor flooding is possible, especially south and east of the city and across Vermont and parts of New York State.

Further west in the Ottawa Valley, less rain is expected, but more snow may fall as that region drops below freezing earlier on Wednesday.

Another component of the storm will be strong winds, gusting up to 70km/h at times. As the storm moves northeast of Montreal, a strong cold front will sweep east bringing much colder temperatures along with a rapid freeze as any leftover rain changes to snow Wednesday night.

Thursday will be windy and colder with clearing skies, a brief break again before yet another storm arrives next weekend with more precipitation.