I bought a house that was on property that was high in the Green Mtns. in VT. The wind would blow harder then any other place I have lived. When that wind combined with snowfall, the problem would occur. The house was new construction by a very fine contractor/builder. When the ceiling started to show leakage, we took a peak up in the attic and there were the piles of snow on top of the blown in insulation. He ended up fixing all of the damage, had the insulation re-blown in, and installed another type of ridge vent - I think it was called a hurricane vent. This solved the problem.