After weeks of cold weather, it seems almost cruel - the bitter temperatures lift and Mother Nature replaces them with the first real winter wallop in about two weeks. And this one will affect both rush hours of your Wednesday commute.

It's all part of a massive disturbance that's delivering a major pummeling to areas in the Ohio Valley. And as bad as things will get here before it's all over, we're getting off easy.

The system brought high winds, mountains of snow and ice nearly four centimetres thick in some places. Cars began spinning out in Dallas, Texas as drivers found it impossible to navigate through the slick conditions.

A school bus went into the ditch in hard hit Oklahoma.

At least 30 centimetres of snow blankets Nebraska.

And thousands are without power south of the border after the bad weather brought down hydro lines.

All of which should comfort the blow of what this monster is going to do in the GTA.

We're just going to get brushed by it - although that still means up to 15 cm of snow.

It's expected to start after 11pm and keep going until at least 5pm Wednesday, making the morning commute and the return home equally treacherous. 

Forecasters originally hoped the storm would give us just 5 cm. But it now appears we're looking at more like 15 cm - and there could be additional accumulations depending on where you are.

Temperatures should stay steady around -7C, so at least it won't be too cold as you clear it all away.

That's allowed the city to cancel its fifth extreme cold weather alert of the year, which had been in effect since last week. But you may well wish the temperatures were still in the deep freeze.

Here's the best guess about the timeline:

11pm Tuesday: Flurries begin, 1-2 cm

2am Wednesday: Snow gets steady and more intense. 2-4 cm

8am : Rush hour arrives but it won't be much of a rush. 3-6 cm of steady snow continues

12pm : Finally tapering off but still accumulating. Another 1-3 cm.

5-8pm : Storm finally moves off and the clean-up begins again.

As far as the morning drive goes, plows don't get out until there's at least 5 cm on the ground.

By 9am, there could be as much as 10 cm on the streets, with up to 12 cm by noon. They'll try to get to the side streets by 3pm, when totals could hit 15 cm. The worst should be over by around 5 o'clock, but the roads will still be a mess as you drive back in the afternoon.

Some sample projected GTA snow totals:

Toronto Downtown: 13 cm

Markham: 14 cm

Brampton: 14 cm

Police are urging drivers to leave early and slow down, after the past few storms led to too many fender benders, jackknifed tractor trailers and spinouts to count.

After this howler passes by, we should be snow free for the rest of the week, with a just a chance of mixed precipitation on Super Bowl Sunday. It doesn't appear we'll see another snow event until next Tuesday - if we have all this cleared out by then and you can find a place to put it all.

BT will be on the air at 5:30am Wednesday to help you get an early start. CityNews.ca will list any cancellations that may result from the big dump. 

See the 7-day forecast here

Check out our exclusive and continuously updated weather webcast here.