Is there even a shadow of a doubt?

I was thinking the same thing, but here's my guess:

-Cold, foggy night/morning = frost forming

-Cloudy until early-morning so the sun doesn't warm the shingles

-Clouds clear up a bit by mid-morning, and the sun rapidly warms up the shingles, leading to the frost evaporating quickly relative to the shadow's motion

Ooookay, got a chuckle out of me man, thanks.

Maybe his neighbor is a climate controlling liberal?