Snow Squall Outbreak Could Cripple Parts of the Snowbelts in Southern Ontario With Locally 40–80+cm of Snow Accumulation by Late Thursday

InstantWeather

So far this year it has been relatively quiet in the snowbelts as we typically see the worst lake effect snow in December. In fact, usually at this point in the winter the Great Lakes are either partially or fully frozen over shutting off the lake effect snow for the rest of the season. That isn’t the case this time around as very cold temperatures flowing into the region combined with a nearly stationary wind coming out of the W to WNW is expected to crank the squall machine into full force.

Before we get started with the details on the main event, it should be noted that snow squalls from Lake Ontario and Erie may affect the southeast portion of the Niagara Region and the southern tip of Prince Edward County at times. The heaviest accumulation should stay stateside but near-zero visibility and maybe 15-20cm locally are possible in those areas. This includes Port Colborne, Fort Erie and Niagara Falls.

Some unorganized lake effect snow has already begun off of Lake Huron and Georgian Bay with the Bruce Peninsula feeling the brunt of it today. We expect during the mid to late morning on Wednesday a squall stretching from Wiarton/Lion’s Head and inland near Parry Sound will begin to intensify. By the early afternoon, it will meander southward bringing whiteout conditions and heavy snowfall to the Hwy 400 and 11 corridors between Parry Sound/Huntsville and Orillia/Midland.

As we get into Wednesday evening we expect two separate squalls to become mostly stationary with one stretching from Lion’s Head and somewhere inland between Gravenhurst and Orillia. It could reach as far east as the Kawartha Lake and perhaps even Peterborough though accumulation will be limited as you get further away from the lakes. The other band will set up off of Lake Huron between Sauble Beach and Saugeen Shores and again could stretch quite far inland at its peak reaching as far as Bradford.

The squalls could remain locked in without much movement all the way into Thursday morning giving the potential for some areas to be under the squall for 12-16 hours. With the hourly snowfall rate potentially pushing 5-10cm it is easy to see how the accumulation could add up quite quickly. While the very organized squalls will begin to break apart Thursday morning we could continue to see some lake effect snow and maybe weaker squalls through to Thursday evening further adding to the totals. While we’ve maxed out at 80cm, it is not out of the question we see some locations pick up near or more than 100cm so that 80cm mark is a rough maximum.

When it comes to the final accumulation by the time this is over late Thursday it is quite tricky to narrow down exact amounts. This is reflected in our forecast as our ranges are quite large with the highest level having a range of 40cm. It’s also important to note that snow squalls are extremely localized and a small shift in its location could result in a significant difference in accumulation.

The two high-resolution models (American and Canadian) we rely on for lake effect event show a slightly different setup. The American is further south putting the heavier snow just north of Barrie and the Canadian is further north putting the heavier snow around Port Carling and Bracebridge. With either scenario, the forecast for Grey-Bruce counties is the same. We have tried accounting for both scenarios but some adjustments could be needed.

If anything changes we will be sure to get that to you either through a quick forecast update or ‘nowcast’ on our Facebook page early tomorrow after additional model runs.