exhaust vent

We have two bathrooms side by side on our second floor. They both have the same exact layout (about 6'x7'). Both have their own separate exhaust fans (Nutone, 80CFM, 1.6amps), but share the same vent to the roof through a Y-shaped connector and flex 4" pipe. When we take steamy showers in...

A large 28" exhaust fan on the roof that is mushroom shaped allows snow accumulation during storms to blow in. Does anyone have a simple solution? One year I covered it with a leaf bag and duct tape. Not the best solution. I googled a magnetic cover which would be cool but only covers for small...