#0381 "Snow Boughs"

This is a painting of low water density snowsquall snow laden on the branches of the Austrian Pine in our front yard at 81 Western Avenue, Schomberg, Ontario during the winter of 1994-95. One part of water can be used to make 15 parts or even 20 parts of light and very fluffy ice crystals. Snowsqualls typically move onshore off Georgian Bay and pass east of Schomberg as depicted in the radar image below. Schomberg is a great place to live. The radar and side view of the snowsquall illustrates these typical Georgian Bay snowsqualls. Barrie may be great but the onshore snowsqualls can be devastating bringing whiteout conditions. .

Sometimes the Arctic winds are more northerly and the snowsqualls can get very close to Schomberg but still remain just to the east. One particular snowsquall swept right over the village and laid down twenty centimetres of the light and fluffy ice crystals typical of the snowsquall process. That is the case that I painted and it brings back all of the memories.

Snowsqualls are a form of severe convection where cold air is directed over warm open water. The intake of heat and moisture from the water surface fuels parallel bands of cumulus convection. Typically the cumulus towers get up to 12000 feet above the ground but can reach even to 25000 producing thundersnow with a thunderstorm. The distance between these bands is determined by the height of the capping layer.

A temperature difference between the lake surface and the atmospheric air at 5000 feet above the surface needs to be 13 Celsius or greater to get the convection going. It also takes about 80 kilometres of fetch over the open water before the cumulus ignite but from that point onward, the line of cumulus can stay intact even as it crosses from lake to lake.

There is much to know about forecasting snowsqualls as they are influenced by upslope, downslope, friction, shoreline shape, frictional convergence, atmospheric lift and even daytime heating. If you know the wind direction and the temperatures involved a meteorologist can give a really accurate long range prediction of the snowsqualls owing mainly yo the fact that the geography of the lake and the land does not change. If that geography does change though we have much bigger problems beside snowfall rates of 10 to 20 cm an hour. Snowsqualls will remain locked in until something changes - most typically the wind direction.

Driving in snowsqualls is dangerous beyond belief. One minute you can be driving safely along with blue skies and great visibility and the next you will not be able to see the hood of your car. Penetrating the side wall of a snowsquall like the one in the above picture might sound like an exciting thing to do but think again. Not everyone slows downs or stops at the same rate and collisions are a certainly. Simply do not drive into a snowsquall. Get off the road and find a safe location.

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