Even if heaving a shovelful of snow at people leaves him wide open, he can otherwise use it as another shield! He doesn't need shield-shield or shovel-shield, though, because it splats in the snow a couple feet from him.

"It's not a weapon! And, c'mon, if we're given catapults, this is just...another catapult!" He's readying another dig in the snow. Watch out. "Trebuchet? Huh, I don't actually know the difference. Eat snow!" It's not an attack he can keep up, not unless he drastically starts reducing the size of his snow piles he's flinging, but one good thing about the work he's putting in on crossbows and swordfighting is arm strength.

So he flings another pile in a wide horizontal arc, aiming to hit as many people as possible. Sadira included.