Video by BenjaminNelson via YouTube
Here’s one example of how snow can come off of solar panels on a roof.
There’s definitely a LOT of variation – angle of the roof, how wet the snow is, how heavy the snow is, ambient air temperature, sunlight intensity, etc. All of these things effect if the snow will just sit there, or if it will slide off.
In this case, it’s a pretty heavy/wet snow. Temperature is right around freezing, and it’s completely overcast. (You literally can’t see where in the sky the sun is.)
This roof is just shy of a 30 degree angle.
In this particular case, the snow just slides right off.
On the other hand, it’s SO overcast that there is very little solar production anyways.
Snow definitely can effect your solar production, you you should consider that if you plan to install solar and live in a snowy area.
Read articles about snow and solar at: https://300mpg.org/?s=snow