One could very well argue that when there is snow on the ground for well over a few hours, they are considered warned. They have a social contract to get rid of the snow, it’s probably considered as if it’s a bor berushas harabim.
What good does posting here do? Just call 311. It’s certainly allowed, it’s not as if you’re reporting an illegal driveway (which is also OK), you’re reporting a safety hazard.