Markham, ON - My blog's focus for this entire weekend will be on the upcoming weekend winter storm. It looks like the system is now going to pass through Ohio River Valley and through the centre parts of Lakes Erie and Ontario, meaning more snow than the Canadian model, and more mix precipitation than the earlier American model. I ran through the system again in WXSIM, and with much different results than before. I can describe it as a combination between the two earlier models:

The storm starts off at 10:30 pm EST (Saturday), when the system centre is just over Mississipi River, and over much of Michigan, Wisconsin, and Illinois. It is now preparing to steer itself along the polar jet stream. The temperature is just at -7 C. The leading edge of the warm front is starting to provide the Greater Toronto Area with a snow shower or two. The warm front remains very stagnant, but is still moving northward very slowly. The warm front is now just over the centre parts of Lake Erie and Lake Ontario, and forms a sort of a path for the system centre to pass through. Snow accumulation could be as high as 6 to 8 cm (2 - 3 inches)  At 12: 30 PM EST (Sunday), the warm front passes through much of the Greater Toronto Area, and the temperature started to rise up to 0 C. The precipitation switched over to some freezing rain, sleet, and wet snow. Southeasterly winds settle in, and gusts could go up to 40 km/h.The sleet continues until 11:00 pm in Sunday night, when the warm front already penetrates deep into Southern Ontario, forming a line of mix precipitation along Northern York Region, Dufferin County, Southern Simcoe County, Barrie, Peterborough, and area. The temperature continues to rise after midnight, peaking at 3 C. At midnight, the precipitation switch over to some moderate rain, but will only last for 3 hours or so. Then there comes a break, with temperature at 3 C. At 3 am on Monday night, a sharp burst of rain settles in. This is the result of the cold front coming in. The temperature drops sharply, falling to 0 C by morning commute (6 am), and the precipitation again changes to some wet snow. We could see a messy drive on Monday morning. The cold front moves through our area, leaving the temperature to drop to an overnight low of -6 C, while the northernly winds howl at a speed of 40 km/h, gusting 70 km/h. Wind chill could dip to negative double digits. The back side of the system still supplying the Greater Toronto Area with some light snow, accumulating up to 3 cm.

Leewards side of the lake will see Lake Effect. However, due to the wind is so strong, the Lake Effect could come as inland as Markham, Vaughan, and even penetrate into parts of North York, and we will experience a snow flurry or two, accumulating no more than 2 cm.

The whole system, as WXSIM is suggesting, 50 mm of liquid equivalent of precipitation, with rainfall amounts 15 to 25 mm, mix precipitation around 5 to 10 mm, snow accumulation 10 to 20 cm (this number may sound big, but the rain coming on Sunday night will melt at least half of it)

These 2 picture denotes a summary of the storm:



The purple line depicts the "Ice Line". North of that line, the precipitation will mainly be snow; south of that, the precipitation will be mainly rain. It seems like the warm front will just stay south of us on Saturday night, and that's why 6 to 8 cm of snow in the forecast.

This one depicts the snowfall forecast:


Notice how the ice line shifted from Saturday to Sunday. Southwestern Ontario will see primarily rain.

I will constantly monitor the storm, and the next update will come tonight at around 8:00 pm EST.

Nick, very insightful!! you have a ggod grasp on this situation, I'm very impressed, I'd be surprised if the coastal doesn't take over earlier and become more intense and hold some sort of frozen precip in over the Atlantic coastal plain all the way down into eastern Maryland, though, we'll see.... Hope to see you on here more often...
Bruce, gmhughes@comcast.net

Good update nick, I like how you point out the warm and cold interaction. Its the whole catalyst of this system.