Weather Discussion - Thurs Feb 24th 2011

A weak system with a trailing cold front will cross Southern Ontario today and with it some light snow and the chance of some freezing rain, especially in southern sections and just to the north of the Lake Erie shoreline. Nothing in the way of much accumulation is expected from any snow that does  fall.
Temperatures today will begin to nudge above the freezing mark with +2 or +3 degrees widely felt across the region from Windsor to the Golden Horseshoe and north of the GTA.

The major weather story today however, will be an approaching Colorado Low which is expected to give upto 20cm of snow for areeas from Windsor through to Hamilton . North of that line, snowfall totals whould drop off significantly. Computer models have been moving the track of the low north and south over the past few runs, so the exact track is still a bit uncertain. What does seem certain however is that areas just on the north shores of Lake Erie to Niagara will see the  most snow from this system. 

The Weather Network has produced this snowfall map... There is a wide margin (10-20cm) for some areas, but as I mentioned above, models are not to sure on the exact track with this. Any shiift further north or south could sifnificantly change the outcome of the snowfall totals. Winds will be strong as there is a strong pressure gradient and this will cause extensive blowing and drifting snow.

This is the GFS surface map for 7am tomorrow morning, you can see the Low moving just to the south of the Great Lakes. Keep an eye on the dashed blue line. That's the freezing line in the upper atmosphere and generally determins whether rain or snow will fall. Notice how close it is to Souuthern Ontario.  

Environment Canada has issued Winter Storm Watches for these regions as significant amounts  of snow and blowing snow can be expected. Upwards of 25cm. These are the areas under the Winter Storm Watch as of Noon today.

There is another storm on the horizon.... first a small area of snow for Sunday, then the main system coming in behind it. The difference with this one, will be a change over to rain as a strong push of milder air moves in to the region. Current models are indicating 25-30mm of rain from this system Monday. That could spell trouble in some areas with the melting snowpack causing some localized flooding.

Long  Range trends are showing a real roller-coaster ride in terms of temperatures over the next 15 days with plenty of precipitation events during that period as well.

Where was the warmest city in Southern Ontario yesterday.....

Hamilton, Kitchener,   +1°C @2pm
Several other cities reached that temperature across Southern Ontario