Snow load is not mentioned when using horizontal panels. In higher latitudes, solar is relatively uncommon because of the sunlight deficit in winter. Panels that are deployed are usually placed at an incline equal to the latitude (or even vertically) to capitalize on free snow shedding and to regularize/maximize year-round minimum output (i.e. bring up winter by bringing down summer). Mounting solar panels flat is sensible from the standpoint of this technology (no solar output needed in the winter, that's what the storage is for!) but may be breaking a lot of ground (and panels) with horizontal panels in snow country.