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Ontario: Double digit days are gone, weekend snow looms

The Weather Network logo The Weather Network 2018-10-23 The Weather Network
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This early week warm-up in southern Ontario is not only short lived, it's likely the last double digit days we'll see in the next several weeks. Tuesday's cold front will send temperatures falling and will spark up the lake-effect snow machine once again. More on the areas of concern for Wednesday morning's commute and a look at a messy storm system that could threaten weekend plans, below.

(See also: Explosive year for tropics; Willa makes 9th Category 5 storm)

WEATHER HIGHLIGHTS:

  • Cold front moves through on Tuesday, cooling temperatures and setting up potential for lake-effect rain and snow
  • Chance for light snow overnight Tuesday and into Wednesday morning as temperatures cool for the Dundalk and Shelburne areas
  • Large upper trough over eastern half of the country keeping the region below seasonal mid to late week with single digit highs for most
  • BE PREPARED: Monitor weather alerts for your area, here 
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LAST DOUBLE DIGIT DAY FOR WEEKS

As temperatures recovered to more comfortably seasonal values on Monday, Tuesday starts out on a similar note, but a cold front will mark the end of double digit days for a while. Although most of the day will be rain-free, scattered rain showers are possible with brief downpours that could mix with small hail/graupel in some places. We also can't rule out a rumble of thunder or two either.

TEMPERATURES FALL, A SHIFT IN THE WINDS

Between Tuesday night and Wednesday, a shift in the winds will bring much colder air back to southern Ontario from the northwest, dropping highs back into the single-digits for most of the region for the rest of the week. And with that cold air comes the renewed risk for lake-enhanced precipitation coming off of Lake Huron and Georgian Bay.

WATCH BELOW: ROUGH TIMING FOR SNOW, RAIN SHOWERS

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WEDNESDAY MORNING COMMUTE TIMES COULD BE JEOPARDIZED 

With that cold air creeping back in, meteorologists are closely watching the Dundalk Highlands region in the pre-dawn hours of Wednesday for the development of lake-effect snow, which could impact the morning commute. 

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In this slightly elevated region, temperatures are expected to be at the freezing mark or below through the overnight hours, leading to potential snowfall accumulation in the area between Mount Forest, Shelbourne, and Owen Sound. A few centimetres of snow are possible during this time, with the potential for it to increase under a persistent lake-effect band.

This could make Wednesday morning's drive along Highway 10 and Highway 6 a little more difficult than usual, so be sure to leave some extra time for yourself that morning if you live in this area.

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Back down in the GTA, and across Ontario in general, cold air will linger over the region until the end of the week, keeping daytime high temperatures in the single digits and around 5ºC below normal into the weekend. On the bright side, after the cold front passes by on Tuesday, mainly sunny skies can be expected across much of southern Ontario to end off the week.

EYES ON A SIGNIFICANT WEEKEND SYSTEM

Looking ahead to next weekend, a significant storm -- born from the remnants of Hurricane Willa -- is expected to track up the U.S. East Coast, while an Alberta clipper dives into the Great Lakes region. The interaction between these features will be the driving factor behind our weekend forecast, and that's making for a tricky forecast. It's possible that this system will remain well to our east with little to no impact. 

A wintry mix, or even the first significant snowfall for some parts of southern Ontario isn't out of the question however, depending on how these systems progress. Higher terrain away from Lake Ontario, and parts of eastern Ontario are more likely to see the flakes fly and this is one story we'll be watching closely for the rest of the week.

FROM THE MET DESK: FIRST LOOK AT POTENTIAL WINTRY WEEKEND

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LAYER UP FOR HALLOWEEN

Colder than normal temperatures are expected to dominate the last days of October, including Halloween, with that chilly pattern persisting into the start of November as well.

"This is NOT the start of winter just yet," says Weather Network meteorologist Dr. Doug Gillham. "There are signs that milder weather will attempt to surge back into our region at times, but at this point confidence is low as to whether the warmer weather will actually make it back into southern Ontario for any significant length of time." 

A more likely scenario would see some back and forth swings in temperature, which are typical for the time of year. 

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WATCH BELOW: EYES ON WILLA - FROM A CATEGORY 5 HURRICANE TO A CANADIAN WINTER STORM

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