Hummm, -10, that's warm (Born and raised in Quebec speaking here.)

Base layers (close to skin) are important. You'll want a good layer + ski pants at the bottom, and more layers on your top parts.

MITTENS. Buy a pair of mittens. They don't have to be expensive, just water resistant. If you pay 30$ you'll have a GREAT pair. You'll find them everywhere around Fernie. With a tiny pair of gloves under them, they will be fantastic and warm. And when you need to use your fingers, you can take off your mittens without freezing your extremities...

TOQUE. Cover your head.

Enjoy the snow! Fernie is supposed to be fantastic!

p.s. The first time I skied here in the West, in Whistler, it was about that, -10, and I was really excited. I had never skied above -15 I think...