Turbine vents, or “whirly-birds”, are great at ventilating and stick nice and high above the snow. The main issue with these is they need to move freely to function properly and to keep out rain. Because they have moving parts, they can get jammed and they have been known to let water into attic spaces. The spinning action is designed to keep out rainwater, but is not 100% effective.
We know of one case where a turbine vent let in a lot of water during a particularly bad storm. The water soaked into the insulation and the insulation became so heavy that it caved in the kitchen ceiling.