Depends. Even at that angle it really depends on how much snow you get. Up to about five inches I would guess you'd be safe. More than that... Just because it is angled doesn't mean all the snow will slide down. Especially if you get blown snow like we do here. Blown snow will build up at the base and give a base to start more upper buildup. And while metal posts are generally good, they aren't set in concrete as far as I can tell. I have used garden posts like those before. They are good, but not great. If memory serves, they go down about 6 inches. My main concern would be them getting pulled up. Some of mine would wobble, even in winter when others I couldn't pull up if I really tried. Depends on your soil and how well/deep you got them.
And speaking of blown snow, if you don't have some kind of door it could blow straight into the coop seeing as how it is directly on the ground.