Canadian Weather Centre – Blog Outreach @ Wordpress – By Amateur Meteorologist Nicholas Tam

Markham, ON – Recall Ice Storm ‘98. A prolonged period of freezing rain has put down power lines and have done millions and millions of dollars of damage to Southern Ontario as well as Southern Quebec. What a nightmare! Could that happen again? Oh, yes it could. In fact, freezing rain makes the major weather story for much of Southern Ontario as well as Southwestern Quebec.

An incoming low from Texas is surging up warm air from the Gulf of Mexico is bringing a powerful warm front that will swipe across Southern Ontario. This warm front will surge up warm air, and rain will fall. Due to the surface temperature is so cold (think of all the snow cover), freezing rain will fall. In fact, when the first bands of precipitation (which will push into the Golden Horseshoe at around 9 am EST) will start off as freezing rain. The 850 mb temperature by then will be at around 2 C (which can sustain rain), but the surface temperature still remains at around -6 C, which creates a perfect environment for freezing rain to hatch.

The warm front will finally push out of Southern Ontario at around mid-afternoon, and the 850 mb temperature plus the warm southernly winds finally “convince” the surface temperature to go above 0 C. At this point, the precipitation will go over to moderate rain, falling up to 20 mm until it dissipates into drizzle by early overnight hours. Then the cold front comes into play into the Golden Horseshoe by Monday Afternoon. Initially, the precipitation will start as moderate rain, then slowly transfer over to moderate snow, accumulating to up to 5 cm.

At this point, it looks like the snow cover for much of Southern Ontario after the storm will be at around 10 to 15 cm.

Also, according to the 18 Z GFS, I will consider the rain/snow line to be drawn at about west to Tobermory and Manitoulin Island, through Wawa, and Sudbury, Nickel Centre, and through North Bay, and up north to Rouyn – Nwanda. Anything south of that will see primarily freezing rain (ice pellets) and rain. North of this line will see all snow.

A winter storm warning and a freezing rain warning are issued to all of Southern Ontario.

Ottawa, ON / Gatineau, QC – Ottawa and area (including Montreal and area) will see precipitation at around 6 hours later than the Golden Horseshoe. In Montreal, precipitation should start at around 1 PM. Majority of the precipitation will be mix precipitation, briefly switching over to rain, then back to snow. Snow accumulation will be at around 15 cm , accompanying with 5 mm of rain. Ottawa will see more of a freezing rain than a mix. Updates come tomorrow.