On Saturday, I chose not to ride because of snow sliding off the fabric cover of the indoor. It sounds like a snake, and while my mare is too decrepit to have a really bad spook, she will spook.
I hand walked her outside instead (not quite good enough footing for riding, but walking was fine.) I kept hearing the snow coming off, and finally took her into the barn to investigate. We stood in the doorway to the arena and watched the snow come off. She popped her head up and got very “big” a couple of times, but did not move a hoof. (Well, until I gave her a cookie after a particularly noisy snow plunge. After that, she wiggled whenever there was a loud noise from the snow, because she wanted another one.)