While it is common to see snow draping off a roof, most only see that as a metal roof issue. To prevent sliding snow from damaging property or the building itself (as some of these shelves can get into the hundreds and even thousands of pounds), snow guards are installed on metal roofs. The reality is any surface if it is slick enough can allow snow slides or shelves to occur, even shingle roofs with a layer of ice in this case.
The next 2 shots were taken 2 days apart, amazing seeing how the icicles started forming on it.