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Another 'hair pulling' Toronto snowfall forecast

Had enough of the winter season
Had enough of the winter season

March 9, 2011 — Meteorologists at The Weather Network are keeping a close eye on a tricky storm that moved into southern Ontario Wednesday.

Messy system for Wednesday
Messy system for Wednesday

Chris Scott, meteorologist

Our forecast team at The Weather Network is starting to go bald. And it’s not a result of genetics.

We’re literally pulling our hair out with another very difficult forecast where Toronto is on the razor’s edge between significant snowfall and almost nothing. In a winter that’s seen its fair share of challenging forecasts, this ranks right up there with the best of them.

A sprawling storm system with a lot of moisture is making its way toward Southern Ontario and Southern Quebec from the Mississippi Valley in the U.S.

Wednesday’s drive to work was relatively uneventful weather-wise in the GTA, but the drive home will be much more interesting. We expect a mix of rain and snow to develop around the shoreline of Lake Ontario Wednesday afternoon, but areas north of the 401 through the GTA are more likely to see significant accumulations of wet snow through the late afternoon and early evening hours. We are confident that the precipitation will change to rain overnight Wednesday for the GTA – the question is exactly what type of precipitation falls for the p.m. commute on Wednesday and how much snow could fall.

Slightly warmer temperatures should keep the precipitation as a rain-snow mix or just rain around the Hamilton and Burlington area. The real question is for areas like Mississauga, Brampton, Toronto, Vaughan, Markham, and Whitby. We think this will be such a razor’s edge difference in snowfall amounts that we are predicting significant differences across the city of Toronto itself – some substantial slushy accumulations in north Scarborough (5-10 cm), with almost no accumulation along the Gardiner in south Etobicoke and south of Bloor St. Frankly, I would be surprised if this works out perfectly, but you get the idea how sharp a cutoff this is in terms of significant snow. A change of 30 km is quite typical with the track of a system and the details a day in advance. Well, in this case, a mere 30 km would change the outcome of the forecast in a big way for a few million people.

Conditions could deteriorate on the roads
Conditions could deteriorate on the roads

This is where communication of the forecast is key. It will be messy afternoon and evening in the GTA, and there will be signficant precipitation. Exactly how much of that will fall as snow and accumulate in any one place is extremely difficult to predict. However, we are reasonably confident that areas along the QEW corridor will be spared significant accumulations, while areas north of highway 7 are likely to see enough accumulation to be a problem.

The bottom line here? Give yourself extra time to get to where you need to go in the GTA Wednesday afternoon and evening.

The most significant snowfall from this storm will occur northeast of Toronto. Areas from Peterborough right through to the Ottawa valley will see significant snow overnight Wednesday. Thursday’s trouble spots will be the Ottawa and St. Lawrence valleys. After a very difficult Monday morning for Montreal commuters, we’ve got another potential mess for Thursday morning.

Oh, and it looks like some more snow will streak across central Alberta, Saskatchewan and southern Manitoba Thursday night into Friday, reinforcing winter’s grip on the Prairie.

Thank goodness April is just around the corner.

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