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An ice storm has been impacting parts of Central and Eastern Ontario throughout the day on Wednesday, leaving thousands of residents without power. The number of outages is expected to continue climbing as freezing rain continues to accumulate on trees and power lines, bringing down additional branches and infrastructure.

While the freezing rain itself is expected to gradually taper off later Wednesday evening, the impacts from this storm are likely to linger well into Thursday in some of the hardest hit regions. Temperatures are forecast to plunge overnight behind a cold front, which means the ice that has already accumulated will remain firmly in place. In addition, increasing winds developing overnight could place further strain on already stressed trees and power lines, potentially leading to additional outages and hazardous conditions.

Because of the combination of icy roads, potential debris from fallen branches, and widespread power outages, there is a strong possibility that school buses will remain off the roads in several of the hardest hit regions on Thursday morning.

However, there remains an important wildcard in the forecast. Some areas may briefly rise above freezing late Wednesday evening or during the early overnight hours ahead of the approaching cold front. Even a few hours above freezing could significantly improve road conditions in some communities by allowing some of the ice to melt before temperatures drop again overnight.

If that brief warm-up occurs in some locations, it could improve travel conditions enough to allow buses to operate in certain regions. Because of this uncertainty, we have chosen not to place any regions into the 90 percent probability category despite the very real possibility that widespread cancellations may still occur.

The highest probability for another ice-related cancellation day is in areas that were particularly hard hit by the freezing rain and that rely heavily on rural transportation routes. These regions often struggle the most with clearing icy backroads and restoring safe travel conditions.

The strongest chance for an ice day on Thursday includes North Hastings under Tri-Board Student Transportation Services and the Madawaska region under the Renfrew County District School Board. These areas appear to have experienced some of the most severe icing from this storm and rely heavily on rural backroads that may remain hazardous well into Thursday morning. Because of this, we have assigned these regions a 75 percent probability of school bus cancellations.

Across the rest of the rural areas in Eastern and Central Ontario that experienced significant freezing rain, we have assigned a toss-up probability of 50 percent. Conditions in these regions could go either way, depending on how much of the brief warm-up occurs and how quickly crews are able to respond to the storm impacts.

These areas include the Upper Canada District School Board, the remainder of the Renfrew County District School Board, including the Pembroke and Renfrew regions, North and Central Frontenac and North Lennox and Addington under Tri Board Student Transportation Services, Haliburton under the Trillium Lakelands District School Board, and East Parry Sound under the Near North District School Board.

In many of these boards, conditions may vary dramatically from one community to another because of the large geographic area they cover. It would not be surprising to see some transportation providers opt for partial route cancellations depending on where the worst icing and power outages remain.

Widespread power outages may also play a role in the decision-making process, even in areas that briefly rise above freezing. If communities remain without electricity or if fallen trees and lines continue to block roadways, transportation providers may still determine that operating buses is unsafe.

Outside of the hardest hit regions, the probability drops fairly quickly. We have assigned a slight chance of 25 percent for Central Hastings, Central Lennox and Addington, and South Frontenac under Tri Board Student Transportation Services, North Muskoka under the Trillium Lakelands District School Board, and Parry Sound and North Bay under the Near North District School Board.

While we are leaning toward buses running in these areas, some communities did receive freezing rain during the day on Wednesday and a number of power outages remain in place. With temperatures falling overnight, any remaining moisture on road surfaces could freeze and produce localized icy patches for the Thursday morning commute.

We have also assigned a slight chance of cancellations for the Ottawa Carleton District School Board. Because this board primarily serves urban routes, conditions typically need to be significantly worse before cancellations are issued. Unless additional damage occurs overnight from continued ice accumulation or falling branches, many urban routes may remain passable. That said, the situation will depend heavily on how much additional icing develops this evening and whether the region experiences any temporary warm up.

Across regions east of Lake Huron, we have assigned a low chance of bus cancellations due to the potential for some scattered lake effect snow overnight into Thursday morning. With winds increasing overnight, there is a small possibility that blowing snow could briefly reduce visibility in parts of the region. However, confidence in this scenario remains fairly low and most areas should see conditions remain manageable.

Finally, there is a very low chance of cancellations for areas north and northwest of the Greater Toronto Area. The primary concern in these regions will be the potential for icy conditions developing overnight as temperatures drop and freeze any remaining wet surfaces from earlier rainfall.

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.