Southern Ontario Lake Effect Snow november 12-13

A temperature gradient of 20C between the lake temperatures and the 850mb temperatures will be setting up with the passage of the strong cold front. A strong WNW flow behind the front with a very low amount of directional shear will make for ideal LES parameters. This may be the first major event of the season. 
Lake huron and georgian bay temps are about 10C:


A 13C temperature difference needs to be present between the lake temperatures and the 850mb temps in order to see heavy bands of LES. By the text output from the NAM coming out of borden airport we can see 850mb temps below -10C for quite an extended period of time. It is the same case for toronto and surrounding areas. This would mean about a 20C temperature difference setting up:

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Looking at the skew-t plot from toronto after the passage of the cold front we can see a W wind with little directional shear. This will allow these bands to form off of the great lakes.

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We can see early LES bands already forming on the NAM 4km WRF off of lake michigan, superior, huron and georgian bay with the passage of the cold front. I am curious to see what the RAP will show when it gets into range.

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12z NAM shows a strong SW then W and eventually a NW flow coming of of lake huron and georgian bay. The strongest bands will be setting up from W to E from 0z to 12z tuesday. Areas in and around the GTA will probably pick up some light snow or a coating but nothing major probably. A similar situation to last weekend will set up except more widespread and intense bands off of the lakes.
SW:

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W:

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NW:

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