#2575 "Cumulus Congestus November Sunset"

#2575 "Cumulus Congestus November Sunset"
11x14 oils

Rainsqualls in autumn develop when cold Arctic air flows over the warm waters of the Great Lakes. Frictional shoreline convergence, fetch, and instability aloft all play important roles just as they due in the creation of snowsqualls. 

During the afternoon after daytime heating from the sun has created additional instability over the land, these squalls penetrate much further inland. The squalls from Georgian Bay and Lake Huron typically reach eastern Ontario and even western Quebec during the peak of the afternoon instability. Such was the case after the cold frontal passage of the Halloween weekend. 

The precipitation virga from these cumulus congestus cells certainly started their journey as snowflakes… most melt but some did not. Only a few reached the ground for me to observe. Snow flakes fall at 1 metre per second as a good estimate. Rain drops fall much faster. The transition from a dense conglomeration of snowflakes falling slowing into a much less dense volume of faster rain drops is typically obvious in those trails of virga wafting from the cloud base. The trails of snow essentially disappear into rain drops. With the definition of virga, non of those rain drops are supposed to reach the ground and thus be observable. If "rain" does indeed reach the ground, technically it is a rain shower. 

A clerk at the grocery store when I went for COVID curbside pick up of our bi-weekly groceries described one of the showers as a mix of hail, freezing rain and snow accompanied by really strong and gusty winds. The convection turbulence with a heavier squall, compacts the snow flakes into ice crystals type B which can hurt like hail when they hit you. There is nil chance of freezing rain but the melting ice pellets, strong convective winds and cold rain shower would make conditions miserable after enjoying a long and hit summer. I parked under the grocery store carport so we would not experience those weather conditions. 

Radar often looks overtop of the relatively shallow convection. The radar will typically only see the pieces of the squalls which are closest to the radar site. Satellite imagery is required to connect the disjointed radar observations, often revealing the linkages that connect the pieces across all of the Great Lakes. Squalls are relatively easy to forecast far in advance. The forecast relies on airmass and lake temperatures as well as wind direction and speed. The geography of the Great Lakes basin is one of the most important predictors of where the impacts will be experienced and these characteristics do not change. One can comfortably predict a squall situation a week ahead of time... 

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