Travellers heading out in southern Ontario Saturday, particularly on the 401 and QEW corridors, should be extra cautious as snow and blustery winds could make for difficult commutes, so they should plan ahead. The amounts won't be overly excessive, with 5-10 cm for a swath along the lakes Erie and Ontario shores extending into eastern Ontario, but when combined with the winds, roads will be slippery and snow-covered, and visibility will be poor. Some areas could also see rain or ice pellets, so that can further add to the dicy roads. More on the timing and impacts, and a look at whether or not to expect a white or green Christmas, below.
SATURDAY: TEMPERATURES DROP, FAR-REACHING SWATH OF SNOW COULD HINDER TRAVEL
The weekend will get off to a messy start in southern Ontario with the low-pressure system staying south of the lower Great Lakes but close enough to clip the region with a potential mixed bag of wintry precipitation including snow, rain and ice pellets.
Snow begun infiltrating southwestern Ontario and the Greater Toronto Area (GTA) Saturday morning. The swath of snow will affect a narrow band along the lakeshores from the Highway 401 corridor through to eastern Ontario.
Because of the warmer temperatures in the southwest, the mixing line will extend along Lake Erie shores from Windsor to Niagara region, bringing a brief period of ice pellets or light rain.
Accumulating snow on untreated roadways will impact travel and motorists are advised to exercise caution. Winter weather travel advisories are in effect for areas along the lakeshores in the south.
"Motorists should expect hazardous winter driving conditions and adjust travel plans accordingly. Be prepared to adjust your driving with changing road conditions. Take extra care when walking or driving in affected areas," Environment and Climate Change Canada (ECCC) says in the special weather statement.
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However, areas on the western end of Lake Ontario extending from Toronto to Grimsby may see higher amounts from potential lake enhancement, while cottage country can expect lesser amounts -- 5 cm of snow or less.
What could also make for difficult travel will be the winds. Reduced visibilty will be possible along with the snow, with easterly winds gusting between 40-60 km/h through the day Saturday, easing in the overnight hours.
Snow should dissipate in the evening for most of the south, with the chance of snow squalls developing in the wake of the system, but it may linger into Sunday morning for eastern Ontario. The south can expect a fair day to end the weekend.
Temperature-wise, daytime highs will be close to seasonal Saturday with values around the freezing mark, though noticeably cooler in cottage country and eastern Ontario. Sunday will be slightly cooler in behind the system, with daytime highs falling into the low minus single digits across the board.
LOOK AHEAD: CHANCES FOR A WHITE CHRISTMAS WILL COME DOWN TO THE WIRE
A fast-moving system from the Prairies will move into northern Ontario Sunday evening, bringing less than 5 cm of snow for the region. It will then reach southern Ontario Monday afternoon with a round of flurries, but no major accumulations expected.
While the pattern next week looks to be more seasonal, changeable conditions are still expected, with exact storm tracks being the key to a white Christmas.
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"A white versus green Christmas will likely come down to the wire," says Gillham. "We are keeping an eye on the potential for a system around Christmas Eve. It is too early to make a call on the exact track and whether that will bring us snow or rain and that will likely be the deciding factor for a white versus green Christmas."
Thumbnail courtesy of Dean Marshall/Submitted, taken in London, Ont.
Be sure to check back for the latest updates on the changeable pattern across Ontario.