1. The snow will usually melt off of the ridge when the heat leaves the space and some air flow will go through the snow. You definitely want something like the GAF Snow Country up there.One of my previous posts was asking about ice dams. Message back was that if the attic is properly air sealed, insulated and vented.... there shouldn't be any problems.
Not having much luck with the venting thing.... the insulation is stuffed into the soffit bays (?) and there is a piece of 4" pipe running down every 3rd bay (instead of a baffle). I should have every bay vented but can't get in from the attic to clear the insulation away (too tight). Will need to pull down the soffits to get at it and sort of want to wait til the spring so I don't slide off the roof with the snow.
Anyways, couple questions...
1) I have a ridge vent at the top cap but this probably applies for other roof vents. In the wintertime when I've got 18" of snow on the roof, the ridge vent is completely covered. Sort of kills the venting, right?
2) Mentioned that I can't do much to fix the venting at this time. What can I do as a stopgap to keep ice dams from forming? I've been clearing the snow with a roof rake (6' up from the edge) to try to keep the gutters clear and it seems to be working.....
2. Installing some sort of heated wire (or other means to melt/keep the snow off) or scraping the roof are your two big options right now.
You definitely want to get that intake air issue fixed up as soon as the weather allows.