Our original roof (26 years ago) has ridge vents with an aluminium cap. The sides had small louvres for the air flow. With blowing snow, some did get through the openings. We would get a dusting of snow in the attic. Never enough to really make anything wet and nothing was ever ruined, but it was an issue. When we re-roofed we put on new vents. I do not know the brand, but the "framing" is plastic. The vent area has something like a plastic steel wool as the barrier. Never had any snow or rain infiltration with the new stuff.
paul
paul