Frosty, the flash-in-the-pan overnight sensation.
This morning the roofs of nearby buildings were white -- instead of black -- at 7 AM. Whether it was actually a thin drift of snow or just a thick frost, I couldn't tell. When the residents heated the insides of the buildings, and the sun the outsides, the white melted in patterns that let you know just where they need more insulation. By 9 it was all gone.
This happens frequently, any night that goes below about 35 degrees, so we've seen it most mornings for the last week.
The apartment buildings, typically three floors, have flat roofs. Office buildings and stores, too. Why would you build a flat roof in an area that gets a lot of snow? I have to investigate that question. I guess that it just isn't *that* much snow to be a real problem.
If the snow is light, just a dusting, there is an interesting pattern on the flat roofs of the buildings first thing in the morning. The snow melts first where more heat comes up from the inside of the building. Judging from the pattern of melting, I guess that the nails holding down the roof material conduct just enough heat up from the inside to make a difference. Every two feet or so, there is a little dark dot in the white covering where the snow has melted on top of a nail head. Just that little bit of metal, instead of wood rafter or joist or insulating material, conducts a little heat from the inside to the outside, and is warmer than the rest of the roof. At least, I think that is what is going on.