Snow can get into any weak areas on the roof as the melting causes ponding which seeps into the building.
Roof vent leak from snow.
The roof must be made colder.
You should inspect your ridge vent annually.
When your roof was installed each vent pipe received a flexible boot to seal water around the round surface of the vent pipe.
Another problem with snow is it could melt and refreeze.
If the fasteners are not secure a strong wind may pull up the ridge cap and let rain or snow get into the vent causing it to leak.
Vent pipe leaks during heavy rain can occur if you have cracks in your vent pipe boot or flashing.
There should be a fastener every 18 inches.
Similar to attic frost related leaks this problem is related to the accumulation of frost inside an exhaust vent commonly a bath vent duct where it travels through an unheated attic.
These boots vary in quality flexibility and longevity.
While you are on the roof walk along the entire length of the ridge vent.
Most ridge vents have a plug at the gable end of the roof so be sure it is there and secure.
To do that install insulation or more insulation in the attic floor and keep it out of the eaves and soffit vents.
Look to see if the fasteners are still in place.
Leaks due to snow or rain driven into the attic through louvres or vents acceptable performance condition attic vents shall be installed in accordance with the building code and prevent the entry of rain snow and insects.