Potential Winter Storm for Central and Eastern Ontario Including Ottawa; 15-25cm of Snow & Freezing Rain Starting Sunday
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While the winter weather season has been quite active in most of Southern Ontario over the past few weeks, Eastern Ontario has largely been spared from the worst of it. However, that streak of luck is about to change as the first significant winter storm is on the horizon, set to begin on Sunday.
Current data indicate that the Ottawa Valley may experience widespread snowfall totals ranging from 15 to 25cm between Sunday afternoon and Monday morning. There is even a possibility of some localized totals exceeding 25cm, though this is expected to be fairly isolated.
Central and Eastern Ontario are also facing the concern of freezing rain, with locally up to 5-10mm of ice accretion possible, while more widespread amounts will be closer to a few millimetres of ice.
The system responsible for this wintry mix is poised to move into our region early on Sunday, initially bringing a combination of freezing rain and snow to Central and Eastern Ontario. As the day progresses, it will transition into more sustained heavy snow, with the most challenging conditions anticipated late Sunday into early Monday morning.
There is also a possibility of freezing rain to the northwest of the Greater Toronto Area, particularly over the higher elevations of the Dundalk Highlands during Sunday morning and afternoon.
For Southwestern Ontario and the Lake Ontario shoreline, precipitation is expected to remain mostly rain throughout the event, with limited impact. However, there could be a transition to wet flurries overnight into Monday morning as the system moves out and colder air follows.
By the evening, freezing rain is likely to transition to heavy snow as colder air settles across the region. This brings the potential for rapid snowfall accumulation in the Ottawa Valley and northern parts of Central Ontario during the evening and early overnight hours.
Hourly snowfall rates might briefly approach 4-8cm at the peak of this event, coupled with 50-70km/h wind gusts, leading to blowing snow and near-zero visibility on roads. Travel is strongly discouraged starting late Sunday into early Monday. We will likely see some school bus cancellations on Monday morning.
Snowfall will persist into early Monday morning, gradually coming to an end by sunrise. Flurries are expected to linger throughout the morning, but significant accumulation is not anticipated.
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Regarding the freezing rain threat, there are two areas of concern with the heaviest freezing rain potential. The first is confined to the higher elevations around the Dundalk Highlands, including Orangeville and Shelburne.
Moving eastward, the freezing rain threat becomes more widespread, covering most of Eastern Ontario and Central Ontario. However, a quicker switch to snow may result in less actual ice accretion than initially forecast.
The highest ice accretion is expected southwest of Ottawa, including Smiths Falls, Bancroft, Kaladar, Arnprior, Orangeville, and Shelburne. This region could see up to 5-10mm of ice by the end of Sunday.
Those in Cornwall, Ottawa, and areas westward into Muskoka may experience a few millimetres of freezing rain primarily during the early part of Sunday before transitioning to heavy snow by Sunday evening.
A critical aspect of this event is its potential impact due to the absence of a substantial warm-up after the freezing rain, which could impede the melting of any ice that forms. Above-freezing temperatures may not return to the region until next weekend at the earliest, ensuring that the ice and snow will linger.
Compounding the situation, heavy snowfall is expected, raising the risk of power outages as accumulated ice and snow will weigh down power lines and tree branches.
The highest snowfall totals are expected along the Quebec border, including Hawkesbury, Ottawa, Arnprior, Renfrew, and Pembroke. Accumulation in this area is projected to range from 15 to 25cm, with the potential for a few locations to exceed 25cm, particularly over the higher elevations west of Ottawa.
A zone extending from Cornwall through Smiths Falls and into Bancroft can expect around 10-20cm of snow from this storm. This region, experiencing the worst freezing rain impact, may be one of the hardest-hit areas from the combined effects of ice and snow.
To the west, widespread totals ranging from 5 to 10cm are expected, extending from Eastern Ontario westward to areas around Lake Simcoe and Georgian Bay. Some models suggest possible lake enhancement off Georgian Bay, leading to locally higher totals of up to 15cm in parts of Simcoe County and Muskoka.
Less than 5cm of snow is anticipated around the Lake Ontario shoreline and in Southwestern Ontario, where precipitation will primarily be in the form of rain. Rain accumulation is expected to range from 5-15mm, with some areas around Lake Ontario, including Toronto eastward into Kingston, possibly seeing up to 15-25mm.
