Freezing Rain Risk and Damaging Wind Gusts Possible Across Southern Ontario on Wednesday

A moisture-laden Texas low is expected to bring a messy mix of precipitation to Southern Ontario throughout the day on Wednesday. The main concern will be the risk of prolonged freezing rain in the higher elevations northwest of the GTA along with parts of Central Ontario during the morning on Wednesday. Combined with strong wind gusts reaching 80-100km/h, particularly through Southwestern Ontario will likely result in some localized power outages in the affected regions. For the rest of Southern Ontario, we are looking at heavy rainfall with generally between 15-30mm of rain accumulation although some parts of Deep Southwestern Ontario including Windsor could approach 40-50mm thanks to some thunderstorm activity later in the day on Wednesday. This may result in some localized flooding so be on alert for that if you live in a flood-prone area.

Precipitation associated with this system will begin to reach our region just after midnight starting as rain for Deep Southwestern Ontario. However, by the mid-morning hour, the precipitation will clash with below-freezing temperatures hovering around -2 to 0°C around the Orangeville and K/W area. This will allow for the development of a band of freezing rain that is expected to last for several hours. Those in the surrounding regions including London, Woodstock, Hamilton and the GTA away from the lakeshore could see some brief freezing rain or ice pellets before temperatures quickly rise above the freezing mark. Another stubborn pocket of cold air over Central Ontario including Algonquin Park and Bancroft will create the environment for some freezing rain here late Wednesday more and into the afternoon.

There is some disagreement among the models on exactly how fast the temperatures will warm up later in the day. One model, in particular, is quite aggressive showing below-freezing temperatures over the Dundalk Highlands lingering into the evening. As a result, that would lead to a fairly heavy icing event of up to 8-12mm of ice accretion possible for the K/W, Orangeville and Guelph region. Although other models show a faster warm-up with the freezing rain risk ending by the mid-afternoon which would limit accretion to 2-4mm max. We’re leaning more towards the 2-4mm outcome as it seems to have more agreement, but do keep in mind that locally up to 8mm can’t be ruled out if the cold air holds on for a few more hours. All freezing rain will come to an end by the end of the day Wednesday as warmer air push into the region. This will also help melt any ice accretion and lessen the impact on the power grid.

As mentioned above, this system will also feature very strong wind gusts mainly during the morning on Wednesday. The strongest wind gusts will be found along the Lake Huron shoreline with the maximum wind gust approaching 90-110km/h in this region. Other parts of Southwestern Ontario can expect gusts around 85-95km/h and 80-90km/h around Lake Simcoe into the GTA. Wind gusts will remain quite strong throughout the day on Wednesday but should begin to taper off as we head into the evening. Aside from the potential wind damage, this will also present an issue when combined with the freezing rain during the morning on Wednesday. Power outages can’t be ruled out in those regions that see both the strong winds and freezing rain.

We are also closely watching the risk of thunderstorms in Deep Southwestern Ontario for Wednesday afternoon and evening. Current data appears to keep the strongest ingredients south of the border so the severe risk should be very low, but the chance is still there that we see an isolated marginally severe storm sneak across the border mainly in the Windsor-Essex region. The main threat would be some small to medium-sized hail and strong wind gusts.