Winter Storm to Dump Up to 15-25cm of Snow on Eastern Ontario Between Thursday and Friday
/UPDATED FORECAST
ISSUED: Thursday, Jan. 12, 2023 (3:00 PM)
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Eastern Ontario continues to be in the bullseye with the highest snowfall totals of this event. However, the latest model data indicates that this system will be weaker than expected and that the overall totals will be lower and more localized to eastern parts of the province.
Based on this change in the data, we have adjusted our forecast by reducing the highest totals from this event down to 15-25cm which encompasses much of the Ottawa Valley. The heaviest snow is still expected to fall during the overnight hours into Friday morning. Snowfall accumulation above 10cm will be mainly found in Eastern Ontario as we have significantly decreased the expected totals around Georgian Bay and Lake Simcoe.
Around 5-10cm of snow is possible from York Region through Peterborough and into Kingston. The Hamilton and Niagara region may also pick up locally near 10cm with lake enhancement off Lake Ontario. Less than 5cm is expected for the rest of Southern Ontario.
ORIGINAL FORECAST
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The start of 2023 has been fairly unnoteworthy when it comes to the weather across Southern Ontario thanks to a mild stretch of temperatures. However, that has come to an end with the arrival of much cooler air this week and a potential winter storm on the horizon over the next few days. We are watching a system expected to affect Southern Ontario starting early Thursday with the risk of freezing rain across Central and Eastern Ontario throughout the day. Later on Thursday, the temperature will drop allowing for the precipitation to transition over to heavy snow. This heavy snow will linger overnight and into Friday which could result in significant accumulation, particularly in parts of Eastern Ontario with up to 25-40cm of snow possible.
The precipitation associated with this system will come in two separate waves starting with the first round of light to moderate precipitation just after midnight tonight. For Southwestern Ontario and the GTA, the main precipitation type will be rain while we see some freezing rain mixing in further north around the Dundalk Highlands and Lake Simcoe. A few hours of icing is possible throughout the morning hours for Orangeville, Barrie, Orillia, Muskoka, Kawartha Lakes and Haliburton. By the late morning, the freezing rain will taper off and either switch over to some wet snow or drizzle as the first round of precipitation moves out. Those in the Ottawa Valley will remain on the cold side of this system and see mainly snow during the early part of Thursday.
Later on Thursday during the afternoon, we will see the second wave of precipitation move into the region starting with the Niagara region and GTA. Moderate to heavy rainfall will be ongoing extending into the evening in this area as the system tracks to the northeast. By the evening, the upper edge of the precipitation will reach Eastern Ontario and clash with the colder air. As a result, there is the potential for some freezing rain during the evening throughout the Ottawa Valley.
Overnight the colder air will become more entrenched throughout Central and Eastern Ontario allowing for precipitation to transition over to heavy snow after the midnight hour. The most intense snowfall rates will be found just west of Ottawa over the Pembroke and Renfrew region. All areas of Southern Ontario will see some snow during the morning on Friday once the switchover occurs but we expect less snow further to the west where less moisture is present. Lake enhancement off Georgian Bay and Lake Ontario could result in locally higher totals in the Collingwood and Hamilton regions.
All precipitation will come to an end by Friday evening as the system moves out of the region.
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NOTE: You can click on the map to open a zoomable image which will be easier to read.
The overall impacts of the freezing rain are expected to be fairly minor due to the limited timeframe and precipitation intensity. We are looking at total ice accretion up to 2mm extending from the Dundalk Highlands and through Central and Eastern Ontario (away from the Lake Ontario shoreline).
Our main focus with this winter storm will be on the potential significant snowfall totals that parts of the Ottawa Valley could pick up by the end of Friday. Current indications suggest the total accumulation will range from 25-40cm for the Renfrew and Pembroke regions. Slightly lower totals are expected throughout the rest of the Ottawa Valley including the city itself picking up around 15-25cm of snow.
For other parts of Eastern Ontario and much of Central Ontario, snowfall totals will approach somewhere between 10 to 20cm although there is some uncertainty due to the extent of the moisture further west. It’s possible some areas around Georgian Bay and Northeastern Ontario could struggle to reach 10cm in total accumulation.
Regions around the Golden Horseshoe will see a general 5-10cm of accumulation, but we could see locally higher totals along the southern Lake Ontario shoreline around Hamilton due to lake enhancement pushing totals close to 15cm. Less than 5cm is expected in Southwestern Ontario where rain will be the main story.
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