Post-Thanksgiving Cool Down to Bring Season’s First Flurries to Parts of Southern Ontario on Tuesday

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The chill is definitely in the air following the Thanksgiving long weekend across Ontario, with overnight lows hovering around the freezing mark in many areas over the past few days.

This is a sharp change from the mild autumn weather we experienced throughout September, which has led to a noticeable delay in the changing of the leaves. While the trees are still taking their time to show off their fall colors, other signs of the season are on the way over the next few days.

Most notably, the combination of colder air and the warm waters of the Great Lakes will create ideal conditions for lake-effect precipitation to develop off Lake Huron and Georgian Bay.

While most areas will see lake-effect rain, it could get cold enough along the higher elevations of the Dundalk Highlands, south of Georgian Bay, for some wet flurries to appear on Tuesday.

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Additional precipitation is expected to move into Northeastern and Central Ontario by late Tuesday. As temperatures approach the freezing mark, some areas may see a transition to wet snow. However, significant accumulation is not expected, as the snow will likely melt almost immediately due to the warm ground, which remains above freezing.

For those who miss the milder weather, there’s no need to worry—there’s a warm-up on the way as we head into the weekend and early next week. Some areas could see daytime highs reaching the upper teens or even low twenties, which is well above the seasonal average for this time of year.

PRECIPITATION TYPE DURING THE DAY ON TUESDAY - MAP FROM WEATHERBELL

On Tuesday morning, most places will wake up to temperatures near the freezing mark, but daytime highs are expected to gradually rise into the mid to upper single digits. The higher elevations around Orangeville and Shelburne may struggle to climb above freezing, holding onto near-freezing temperatures throughout the day.

Lake-effect rain is expected to continue south of Georgian Bay throughout Tuesday, and some wet snow could mix in over the Dundalk Highlands during the day. This potential for flurries will be highly localized to the higher elevations between Owen Sound and Orangeville, while areas outside this region are likely to avoid the season’s first snowfall for now.

With temperatures hovering near or just above the freezing mark, significant accumulation is unlikely, as most of the snow will melt upon contact with the ground. However, there is a chance of a few wet, slushy centimeters in very localized areas.

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PRECIPITATION TYPE DURING TUESDAY night - MAP FROM WEATHERBELL

As we move into the evening and overnight hours, temperatures will again drop to near the freezing mark across Central, Eastern, and Northeastern Ontario. With scattered showers arriving from the north and east, there is a possibility that some of this precipitation could fall as wet flurries overnight and into early Wednesday morning.

Accumulation will remain a challenge due to the relatively warm ground. However, those in Huntsville, Algonquin Park, and the Ottawa Valley might catch a glimpse of their first snowflakes of the season. The chance of snow will diminish by late Wednesday morning as lake-effect precipitation weakens and any lingering showers move out of the region.

As mentioned earlier, we’re expecting a gradual warm-up for the rest of the week, though the mornings will still start off chilly, with temperatures in the single digits. The real warming trend will kick off on Friday, with temperatures climbing into the upper teens and possibly even approaching the low twenties in Southwestern Ontario and around the Golden Horseshoe.

This milder weather is expected to continue through the weekend and into early next week.

Snowy Surprise: Parts of Ontario & Quebec Could See Season’s First Snowflakes This Weekend

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As we enter the first full weekend of meteorological fall, Mother Nature is set to deliver a taste of autumn across Ontario and Quebec. A brief blast of cold air will cause temperatures to drop near the freezing mark during the pre-dawn hours on Saturday and Sunday.

Precipitation currently affecting Southern Ontario is expected to linger throughout the weekend. The heaviest rainfall totals are expected overnight Friday into early Saturday in Eastern Ontario, with localized amounts of 20-40 mm of rain possible.

The bigger story is when that precipitation wraps around into Western Quebec and Northeastern Ontario later on Saturday, continuing into the early morning hours of Sunday. With temperatures cooling into the low single digits and even colder air aloft, some of that precipitation may fall as wet snow.

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It appears that locations like Timmins, Cochrane, Kirkland Lake, Temiskaming Shores, Deep River, and Algonquin Park in Ontario could see their first snowflakes of the season. In Quebec, areas such as Ville-Marie, Rouyn-Noranda, Amos, and Val-d'Or may also experience wet snow.

While it's unlikely that snow will accumulate, as it will be mixed with rain and ground surfaces are still too warm, there's a chance that colder-than-expected conditions could lead to a few slushy centimetres in some areas. Any accumulation will melt quickly after sunrise on Sunday as temperatures gradually rise.

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Speaking of Sunday morning, this is when the coldest air of this brief "cold snap" is expected across Ontario and Quebec. Morning lows will likely drop into the single digits across much of Northern and Southern Ontario and Quebec. In Northeastern Ontario and the Algonquin Park region, temperatures could dip to near freezing during the pre-dawn hours, increasing the risk of frost in addition to the potential for wet snow.

Further south, the coldest temperatures in Southern Ontario will be in the higher elevations of Central Ontario, east of Muskoka, where temperatures may plunge to around 2-5°C. It will be moderately warmer in Southwestern Ontario, the Golden Horseshoe, and Eastern Ontario, with morning lows ranging from 5-10°C. Those along the shorelines of Lake Ontario, Lake Erie, Lake Huron, and Georgian Bay will benefit from the warmer lake waters, keeping temperatures above 10°C.

In Quebec, expect low to mid-single-digit temperatures in the western portion of the province near the Ontario border on Sunday morning. Eastern Quebec, including Montréal and Québec City, will see lows in the upper single digits, ranging from 6-12°C.

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WATERSPOUT RISK FOR GREAT LAKES ON SATURDAY MORNING (SORUCE: ICWR)

This cold air will also contribute to a potential waterspout outbreak over the Great Lakes this weekend. The highest risk is on Saturday, especially in the morning and afternoon, with a focus on Southern Lake Huron and Western Lake Erie. Waterspouts are also possible over Southern Georgian Bay, Western Lake Ontario, and even Lake Simcoe.

While waterspouts rarely threaten land, they can be hazardous for those on the water. In rare cases, waterspouts can come ashore, causing minor damage along the immediate shoreline.

The waterspout risk will persist into Sunday, with a focus on Eastern Lake Ontario.

Looking ahead to next week, warmer weather is expected to return to Ontario and Quebec. By late in the week, temperatures could climb back near the 30°C mark in Southern Ontario. So, while this brief taste of fall may be shocking, it looks like summer isn't quite finished yet.