We have 2-story house built in 2000 with a walkout basement without any mature trees nearby. We live in southeastern South Dakota and have frequent snow storms with high winds.

We have had about 12 inches of snow so far this season. For the past week or so it has been quite cold, but yesterday we had a warm up to about 30 degrees. My wife noticed that water was dripping from the vaulted ceiling in our 2nd floor master bedroom. I crawled up into the attic and discovered a small pile of snow (little less than 1 cubic foot) lying on top of the blown-in insulation. I removed the snow as best I could and also pushed back the insulation to allow the drywall opportunity to dry. The remaining roof vents in the main attic had little to no snow below them.

Our garage has a separate attic space with two roof vents so I thought I had better check those out as well. One of them had pile of snow that was approximately 2 cubic feet. The other one had just a trace.

Short of replacing the roof vents with ones that are supposedly designed to keep the elements out what can I do to keep the snow out? I mentioned this issue to a friend and he said after 3 winters of getting snow in his attic he some how opened up each roof vent from the top and zip tied a piece of screen over the primary circular opening inside the roof vent. The problem with that approach is it is now winter and we have a steep roof. I don't know the pitch, but I am fearfully of walking on it in the summer.

I had thought of buying some furnace filters (or some other similar material), cutting the material to fit and stuffing up into the roof vent from the inside. My concern with that is that a furnace filter is designed for air to flow one way and it would seem to me the air needs to flow both ways; in and out of the roof vent. Another idea I had was to put a hair net over the top which I think I could do from the inside. I have also read some other sources suggesting steel wool or Brillo pads.

Certainly someone else has had this issue. Right? Just looking from some ideas and judgement on my ideas.