A Christmas Miracle for Southern Ontario As White Christmas Looks Likely in Most Areas; Potential Storm Christmas Eve Into Christmas Day

This is a PRELIMINARY outlook - we will be updating it throughout the week as we get closer to Christmas.

It has been a roller coaster start to the season across Southern Ontario with fairly mild temperatures and very little in the way of snowfall accumulation or winter storms. Although that does appear to be changing just in time for Christmas so most areas across Southern Ontario has a very good chance to wake up Christmas morning with snow on the ground.

The last weekend before Christmas will feature classic winter-like weather with temperatures near or slightly below the freezing mark and accumulating snow. The heaviest snow will be found through Central Ontario with between 5-10cm of fresh snow accumulation by the end of Sunday. As we head into the start of the week, temperatures will continue to be a few degrees within the freezing mark - likely not warm enough to melt through the existing snowpack in Central Ontario and Northeastern Ontario. Another weak system is expected to move across Southwestern and Central Ontario providing a few more centimetres overnight Monday into Tuesday.

Now with days remaining for the big day, milder air is expected to work its way into the province on Wednesday causing the temperature to rise into the mid to upper single digits. This is especially true within Extreme Southwestern Ontario around the Windsor areas with daytime highs around 7-9°C on Wednesday. The very limited snowpack in this area likely won’t survive temperatures that high so a White Christmas may not happen southwest of London. Christmas Eve will complicate this forecast even more because another day of warmer temperatures is expected on Thursday and this will also extend into Central and Eastern Ontario. A messy system likely starting as rain for most areas appears to move into Southern Ontario during the day on Thursday. If this doesn’t change, it could wash away the hope of a White Christmas for many.

Latest raw model data from the American model (GFS) showing the potential precipitation type Thursday evening (Christmas Eve) - NOTE: This is raw data and isn’t an official forecast. It will change as we get closer. We will have a detailed forecast in the coming days.

BUT not all is lost! Not only Santa Claus will be busy on Christmas Eve, but it looks like Mother Nature might deliver a Christmas miracle across Southern Ontario. The latest model trends suggest that the system affecting our region on Thursday may further intensify as cold air wraps in behind it. Rain will transition over to heavy snow late Thursday into Christmas Day. If it pans out, Southern Ontario could be looking at a fairly significant Christmas Day snowstorm with accumulation between 15-30cm somewhere in the region. Obviously, this will likely change as we get closer but it’s worth a mention at this point. Normally we’d be concerned about holiday-related travel, but with the current pandemic and recommendation for everyone to celebrate within their own household, it should have a limited impact. We’ve been cautious with our White Christmas outlook for this reason as it’s highly dependent on this potential snowstorm. We will be updating this outlook as we get closer and it becomes more certain on how the storm will affect our region.

On behalf of the entire Instant Weather team, we’d like to wish everyone a happy and joyful holiday season! We’ll continue to be here keeping you informed on any impactful weather over the holiday season and into the New Year. Here’s hoping that 2021 is much better to everyone than the dumpster fire that 2020 has been! :)