What type of precipitation most commonly occurs in the boreal climate region in canada?

I think much of the boreal region if fairly flat, so except for the limited mountain regions, you would not expect orographic. It’s pretty far north to get that much convectional precipitation, also, although in the summer months there is some in the southern regions.

For those reasons, I would expect that frontal precipitation would dominate.

Frontal and convectional. Orographic precipitation occurs in the mountains.