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Snow squalls are expected to redevelop this evening across the Bruce Peninsula and then push east of Georgian Bay overnight. These squalls have the potential to be quite intense, bringing periods of near-zero visibility and rapid snowfall accumulation. The greatest impacts are expected across the Parry Sound and Muskoka regions, where totals could approach 25 to 50 cm by the end of Thursday.

With treacherous road conditions likely already in place by the morning commute and snow squall activity expected to persist into the afternoon, it is almost certain that the hardest hit regions will see another day of school bus cancellations on Thursday.

Our highest confidence for a snow day is focused on the Parry Sound region within the Near North District School Board and North Muskoka under the Trillium Lakelands District School Board. These two areas are expected to be directly under the most persistent snow squall activity overnight, leaving little doubt that conditions will be unsafe for buses to operate. As a result, we have assigned both regions a 90 percent chance of a snow day.

We also have strong confidence that East Parry Sound, under the Near North District School Board and South Muskoka within the Trillium Lakelands District School Board, will see bus cancellations on Thursday. That said, there is slightly more uncertainty with these zones. In East Parry Sound, it remains unclear how far inland the strongest squalls will reach. For South Muskoka, guidance suggests the most intense activity may remain just to the north during the morning before sagging southward later in the day.

While a strongly worded Environment Canada snow squall warning is in effect and would typically be enough to justify cancellations based on expected afternoon conditions, recent decisions show that TLDSB may be willing to roll the dice if a region is not directly under a squall during the morning bus run. Because of this, we have assigned South Muskoka a slightly lower, but still strong, 75 percent chance.

Farther north and east, additional regions that could see a snow day due to Georgian Bay activity include North Bay under the Near North District School Board and Haliburton within the Trillium Lakelands District School Board. These areas may see occasional bursts of snow squall activity on Thursday, but it remains uncertain whether impacts will be persistent enough to reach cancellation thresholds. Because of that uncertainty, we have gone with a 50 percent chance, as it could genuinely go either way.

Across the remainder of Central and Eastern Ontario, the chance of cancellations drops off quickly. Snowfall is expected to be limited in most of these areas on Thursday, and any lingering impacts would mainly be tied to cleanup from the Alberta Clipper rather than active weather. We have maintained a low chance for some rural school boards simply to account for the outside possibility that backroads are still not fully cleared by morning, but this scenario remains very questionable.

UPDATE (8 PM): Following the issuance of a snow squall watch by Environment Canada after this forecast was published, we have made a few adjustments to the probabilities for the Bluewater District School Board and the Avon Maitland District School Board.

For Bluewater, the Bruce Peninsula has been increased to a 90 percent chance. Southampton, Owen Sound and Meaford have been bumped up into the 75 percent category, while Kincardine and Hanover have been raised to a 50 percent chance.

For Avon Maitland, northern Huron and northern Perth counties have also been moved into the 50 percent zone.

All other regions and probabilities in the forecast remain unchanged.

In Southwestern Ontario, the main area of concern continues to be the Bruce Peninsula under the Bluewater District School Board. Ongoing snow squall activity here supports a strong 75 percent chance of bus cancellations, with conditions expected to remain hazardous through much of the day.

Just south of that core snowbelt zone, probabilities begin to taper off. We have assigned a 50 percent chance to Southampton, Owen Sound and Meaford within the Bluewater District School Board, where squalls may clip the area at times.

A 25 percent chance has been assigned to Kincardine and Hanover under Bluewater, along with all regions of the Avon Maitland District School Board. In these areas, snowfall amounts are expected to be lighter, but gusty winds combined with patchy lake effect snow could still lead to localized travel concerns.

For the rest of Southern Ontario, school bus cancellations are not expected on Thursday. Conditions should be manageable in most regions, particularly outside of the snowbelt. We have kept a very low chance for a few rural boards in Southwestern Ontario to account for blowing snow and some light snow moving through during the morning, but confidence in cancellations outside the main snow squall zones remains quite low.

Disclaimer: Instant Weather has zero authority when it comes to bus and school closures.

It is completely up to the school boards, bus companies, local authorities, and parents to decide what is best for their children. This is our best guess based on our forecast.