Ice Storm in Southern Ontario. December 1st, 2019.

In what made for a very complex forecast several days in advance, early morning December 1st was a day that just about everyone that follows the weather had on their minds. While I usually try to start forecasting synoptic scale storms several days in advance, there was so much model disagreement - even a day or two out - that I decided to wait until the night before to really dive in.

There was a lot of disagreement on how far the 850-700 mb above zero temperatures would reach and how long they'd stay above zero with the upper level cooling moving into southern Ontario. This is key because temperatures above 0 C at this level, with below zero at the surface (especially when mixing in surface easterly winds that aren't too strong) leads to a significant freezing rain threat. Models had shown that the early morning precipitation band would be strong, so whether the threat was rain, freezing rain or snow, it would likely be intense.

In my area (Grimsby, Ontario), we received no snow. It was all freezing rain (and maybe a few brief periods of ice pellets). I'd estimate much of the Grimsby region received around 15-20mm of ice accretion, which is significant, and more than I had anticipated. Areas west and south of Hamilton, which were further away from Lake Ontario's warming effect, also received significant freezing rain. There were 30,000+ people without power as of mid-afternoon Sunday. 

I'll leave you with more pictures below. I do wish I had captured more weather forecasting screenshots to illustrate how the event transpired, but these pictures will have to suffice.

Area of highest accretion. Not coincidentally, it was where trees fell.