Clouds are great and a super forecast teller. I'm not a meteorologist, but love watching weather like all Canadians. (we're all actually weather phobics)
The clear section in the back is cold and under pressure, (high pressure) so that accounts for the long cloud edge. In this situation, the cold and pressure are also on top pushing down on the moisture and crushing it with intense "pressure". The photo represents the crest portion of a wave at the beach as it comes crashing in. Stop sometime and look at wave photos to see the beauty of the flow and you'll see the same pattern as what you've captured above.
All in all, to get a really good idea would be imaging yourself inside a non-breakable glass box during a tornado. That's what's going on in this photo, but you just can't see it.
This is definitely a keeper shot.

WoW! Thanks for the very informative comment! I wish I was somewhere else with a better landscape instead of my neighbor's backyard.