Odd snow effect

There is this odd drifting effect that occurs on roofs. On one side of the roof, you will get an overhang that grows and grows. It will continue to grow with new snow sticking to the old snow until it drops of its own weight. It happens only on the front of our house. No other sides. In the back yard, it happens only on the front of the tractor shed. I have to knock it off of the house so that it doesn't drop on anyone (It can get quite heavy). We don't go into the back yard in the winter, so that one just grows.


Here is what the shed's roof looks like without snow. By the way, I know the shed looks like crap, I intend to have a new one built soon.
Here is the drift well on its way.