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Winter Storm Outlook
Valid: Sunday, December 1, 2019 - 12AM to 11:59PM
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Forecast Discussion
Issued: Friday, November 29, 2019 - 3:05PM
Forecaster: Brennen Perry
A winter storm is expected to impact Southern Ontario on Sunday with a mixed bag of precipitation depending on your location. We’ll begin with the regions that will see the least impact from this storm which includes Windsor, Leamington and Chatham where the predominant precipitation type will be rain with temperatures several degrees above the freezing mark. Between 10-20mm of rainfall accumulation is possible in this area.
Moving to the north, the potential for a prolonged period of freezing rain exists in areas around the southern shoreline of Lake Huron eastward through the Niagara Region. Freezing rain will begin around 3-4 am starting with the Sarnia area and reaching the Niagara region by 8-9 am. Indications suggest that the warm air will struggle to make it to the surface resulting in the freezing rain lasting for hours without transitioning to rain. The freezing rain will finally end during the early afternoon hours as the precipitation moves out of the region, but temperatures will still be near the freezing mark so impacts will likely continue to be felt for much of the day. The total ice accretion from this event will range from 5-15mm although it’s important to note that not all of the freezing rain will stick to surfaces so actual accretion could be less.
As we go further to the northeast, the predominant precipitation type will become ice pellets with maybe some freezing rain and wet snow mixed in roughly north of a line extending from Kincardine to Hamilton. This includes much of the GTA, Orangeville, Guelph and Owen Sound. There is some uncertainty exactly how much snow will mix into this region and such if we see fewer ice pellets and more snow it’s possible that snow accumulation could exceed 5-10cm. Precipitation in this area will begin around 7 am and continue well into the evening before transitioning over to light snow as the system exits our region.
The heaviest snowfall is expected throughout Central Ontario north of Lake Simcoe and into parts of Eastern Ontario (including areas north of Lake Ontario) where between 10-25cm of accumulation is possible. Snow will begin around Georgian Bay around noon continuing well past the midnight hour and into Monday with light to moderate snow. Models disagree on exactly how heavy the snow will be with some on the lower side between 10-15cm and others showing as much as 30cm so hence why our range is so large right now. We’ll hopefully be able to narrow it down as we get closer to the event - this isn’t our final forecast and it may still change substantially when we release our detailed forecast on Saturday. Be sure to check back for the latest!
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