The New Year to Start With a Bang Across Southern Ontario With a Messy Winter Storm; 10–20cm of Snow and Prolonged Freezing Rain Possible From Friday Into Saturday

The parade of what feels like never-ending winter storms for Southern Ontario continues into 2021 with another wintery blast expected on Friday continuing into Saturday. And unlike previous storms, Eastern Ontario will not be spared from the winter weather as they are expected to be the ‘winner’ when it comes to snowfall from this event. Parts of Eastern Ontario could see as much as 20cm of snowfall accumulation by Saturday. Further south, we’re looking at a messy mix of precipitation including the threat of prolonged freezing rain through the Sarnia, London and Hamilton corridor.

Precipitation will start during the early afternoon hours on Friday as the moisture associated with the system pushes in from the south over Lake Erie. So areas like Windsor, Chatham-Kent, Sarnia, London and the Niagara region will see the first effects during the early to mid-afternoon hours. Current indications suggest it’ll start as a messy mix of wintery precipitation with rainfall along the Lake Erie shoreline and into the Windsor-Essex area. Away from Lake Erie, we’ll see a swath of heavy freezing rain develop from Sarnia along Hwy 401 into London and Hamilton. Heavy freezing rain will continue into the early evening hours with the worst impacts during the dinner hour.

As we head into the evening we’ll see the precipitation spread to the north and east reaching the rest of Southwestern Ontario into the GTA around 6-8 PM. We’d normally put together a timeline map for this system but it’s way too tricky as the precipitation type will be switching from snow, freezing rain, ice pellets and regular rain constantly throughout the evening hour. Expect more rain mixing in closer to the lakeshore especially during the overnight hours. Through the higher elevations and away from the lakeshore we’ll see more snow and ice pellets. Colder air will flow in early Saturday morning which will cause the mix to transition over to wet snow and flurries. A few hours of heavy snow through all of Southern Ontario is likely as the system moves out Saturday morning resulting in a couple of centimetres of fresh snowfall accumulation.

Moderate to heavy snowfall for Eastern Ontario will come in two waves beginning with late Friday evening continuing overnight. Another round of what will likely be the heaviest snowfall will move into Eastern Ontario during the morning on Saturday. Expect very poor driving conditions overnight and into Saturday morning with heavy snow causing near-zero visibility. The storm will come to an end during the early part of Saturday.

Due to the constantly changing precipitation type, it will also make pinning down the exact accumulation pretty hard. So keep in mind that the exact impact will vary even within a small distance. With that being said, for Extreme Southwestern Ontario from Windsor and along the Lake Erie shoreline we expect mostly rainfall with totals between 20-40mm although some freezing rain may mix in for a few hours early Friday afternoon.

As we’ve mentioned, a zone stretching from Sarnia through London and into Hamilton has the potential for several hours of freezing rain which might be quite intense at times. Potential ice build-up of between 4-12mm is possible before the switch over to rain later in the evening on Friday. While not shown on the legend, this area may also see 15-30mm of rainfall accumulation and trace to 5cm of snowfall early Saturday morning.

For the northern parts of Southwestern Ontario and into the GTA we expect a mix of snow, sleet and freezing rain with some rain near the lakeshore. Snowfall totals around 5 to 10cm along with a few millimetres of ice build-up is possible. Ice pellets could reduce the potential snowfall accumulation in some areas.

For Eastern Ontario, the main precipitation type will be heavy snowfall with some ice pellets mixing in close to the Lake Ontario shoreline. Snowfall accumulation between 10-20cm is expected for much of Eastern Ontario from the Kawartha Lakes through Bancroft and into the Ottawa Valley. Less moisture is expected into Central Ontario including east of Georgian Bay where between 5-10cm accumulation is likely. Northeastern Ontario will be mainly unaffected by this storm with less than 5cm of accumulation.

From the entire Instant Weather team, we’d like to wish you a Happy New Year! Hopefully, 2021 will be much better for all of us.