Close Call for Second Wave of Multi-Day Snowfall Event Across Southern Ontario; 10-20cm Possible for Niagara and Extreme Southeastern Ontario on Thursday

IMPORTANT: This map is for ADDITIONAL snowfall from Thursday Afternoon to Friday Morning. Our forecast for the first wave HERE still applies until Thursday Morning.

Widespread snowfall continues across Southern Ontario as the first wave of the multi-day snowfall event brought rain to start and then transitioned over to snow later in the day. Most areas throughout Southwestern Ontario and into Central Ontario are still on track to see between 10-25cm of snow by Thursday morning as covered in our forecast from Tuesday. Now our focus turns towards the second wave which will begin to affect Southern Ontario after the first round tapers off late Thursday morning and continue into early Friday.

The latest data suggests that the second wave of precipitation will track further to the southeast making for less of an overall impact on Southern Ontario. Initially, we thought it could deliver another 10-25cm of snow on top of what we received from the first round. Those higher totals will now be reserved for the Niagra region and into Eastern Ontario along the American border. Regions roughly northwest of a line from Windsor through K/W and Ottawa will see very little accumulation from the second wave with a very sharp cutoff between heavy snow and no snow.

With this southeasterly change in the track, it appears that there won’t really be a break in the snow between the two waves. To avoid confusion, we’re still treating it as two different waves so heavy snow will be ongoing throughout the afternoon stretching along the Lake Erie shoreline and into the Niagara region. This will also move across Lake Ontario and into Eastern Ontario hugging the St. Lawrence River.

The more persistent snow will be found southeast of a line from Leamington through Hamilton and Smiths Falls with the worst conditions during the late afternoon and evening on Wednesday. The Niagara region and into Extreme Southeastern Ontario including Brockville and Cornwall can expect around 10-20cm of additional snow by the time the snow ends early Friday. Some localized totals could approach 25cm particularly over the higher elevations of the Niagara region but aren’t guaranteed.

Other surrounding regions including Norfolk County through eastern sections of Hamilton and into Kingston can expect around 6-12cm of snowfall accumulation from this system. Areas just to the northwest of this line including Windsor, London, K/W, the GTA, Peterborough and Ottawa will see at most a few centimetres of snow from this wave. However, the gradient is quite tight with this one and a slight shift could increase the totals in those areas closer to 4-6cm so pay attention to the local ranges.

Snow will continue overnight into early Friday morning. It should lighten fairly quickly after midnight and fully clear out of the province by sunrise on Friday. If possible, try to delay any travel until Friday if you are in the affected region. Heavy snow late Thursday combined with 30-50km/h wind gusts will make for poor driving conditions.