Disruptive Winter Storm Targets Southern Ontario Starting Thursday With Heavy Snow and Significant Freezing Rain Risk
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The next few days are going to be quite messy across Southern Ontario as our first winter storm of the season takes aim at the region. The exact impacts of this storm will be very location dependant ranging from up to 15-30cm of snowfall accumulation to a prolonged freezing rain risk. In addition to the wintery weather, strong to damaging wind gusts are expected to accompany the system on Thursday which could pose additional risks when combined with the heavy snow and freezing rain.
Precipitation in advance of the approaching low-pressure system will reach Deep Southwestern Ontario by the early hours of Thursday. This system will tap into some warm air from the Gulf of Mexico which is expected to clash with the colder air currently over the province. The warm air will win out for regions further south including Windsor, Leamington, Chatham and along the Lake Erie shoreline. As a result, precipitation here will predominantly fall as regular rain with minimal impact.
With the precipitation spreading further to the northeast throughout the pre-dawn hours on Thursday, the cold air will become trapped at the surface as the warmer air overtakes it at higher levels of the atmosphere. This will allow for the development of a band of freezing rain stretching from Sarnia through London and into the Hamilton/Niagara regions by the mid-morning hours. Several hours of freezing rain is possible especially for higher elevations away from the shoreline of Lake Huron and Erie which could experience heavy prolonged freezing rain throughout the morning.
The battle between the cold and warm air will continue as the precipitation approaches the GTA and Central Ontario by the late morning and early afternoon. This time, it appears the cold air will retain control at all levels of the atmosphere resulting in the predominant precipitation type coming in the form of heavy snow or ice pellets. Meanwhile to the southwest, the freezing rain risk will come to an end as it switches over to a rain/snow mix by the afternoon.
Persistent heavy snow will continue through the afternoon and evening around the Golden Horseshoe and into parts of Central and Eastern Ontario. Expect a very slow and messy evening commute on Thursday with road conditions likely to be very poor when combined with the wet snow and strong wind gusts.
We should see the precipitation slowly taper off overnight and into Friday morning from west to east. However, Eastern Ontario will continue to experience light to moderate snowfall throughout the day on Friday as the system stalls out over New England with precipitation wrapping back around into Eastern Ontario.
NOTE: You can click on the map to open a zoomable image which will be easier to read.
The first effects of this storm will begin to be felt just after midnight as the wind starts to pick up in the southwest, especially around the Lake Huron shoreline. Strong to damaging wind gusts are expected to dominate the story throughout the early morning hours on Thursday with the strongest gusts being found around Lake Huron ranging from 90-100km/h.
Further inland, gusts will range from 70-90km/h for much of Southwestern and Central Ontario along with the Golden Horseshoe. Less of an impact when it comes to the wind is expected for Eastern Ontario with gusts maxing out at around 50-70km/h. We expect that the damaging wind gusts will diminish by the late morning or early afternoon on Thursday, but they could remain quite strong throughout the day.
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NOTE: You can click on the map to open a zoomable image which will be easier to read.
As mentioned earlier in the forecast, the impacts of this winter storm will vary across Southern Ontario with freezing rain in the southwest, a messy mix in between and heavy snow throughout Central and Eastern Ontario. The easiest part of this forecast will be the Windsor and Chatham region which is expected to remain on the warm side of this storm with rainfall totals ranging from 10-25mm over the next 48 hours.
As we move further to the northeast, a few hours of freezing rain is possible during the mid-morning hours for the Lake Huron shoreline, Sarnia, St. Thomas and the Niagara region before transitioning over to rain. Expect around 2-6mm of ice accretion along with 5-10mm of rain after the switchover occurs later in the morning.
The threat of more prolonged freezing rain will exist for areas inland east of Lake Huron (such as Listowel and Stratford), through London and into Brantford. Freezing rain here could linger throughout the morning and into the early afternoon with total accretion ranging from 6-12mm. This amount of ice accumulation combined with the strong wind gusts could result in localized power outages along with very icy conditions on untreated surfaces.
Closer to the GTA, the exact precipitation type becomes less clear with a mix of freezing rain, ice pellets and snow possible for locations including Owen Sound, Fergus, Guelph, Hamilton and Oakville. This area we’re less confident about this as a slight shift in the temperature gradient could result in more snow if it’s colder than expected or more freezing rain/ice pellets if it’s warmer than expected. So don’t focus too much on the exact accumulation because it will likely get tricky to quantify with the multiple precipitation types. Either way, this wintery mix will make for quite the mess out on the roads.
NOTE: You can click on the map to open a zoomable image which will be easier to read.
The focus for those on the colder side of this storm which includes all of Central and Eastern Ontario along with parts of the GTA will be on heavy snowfall and ice pellets. Locations along the Lake Ontario shoreline through the City of Toronto and into the Dundalk Highlands (Orangeville, Shelburne, Collingwood etc.) will mainly see snowfall with totals ranging from 10-20cm by the end of Friday. Ice pellets may also mix in at times, but limited accumulation from ice pellets is expected.
For snow lovers, you’ll want to be north of the GTA in a zone encompassing Newmarket and east throughout Eastern Ontario including Peterborough, Bancroft and Ottawa. This area is on track to see the highest snowfall totals from this event with between 15-30cm of snow expected by Saturday. Regions east of Georgian Bay will mainly see snow as well, but the snow is expected to be less intense so total accumulation here will top out at around 10-20cm.
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