And to the point of the question; I honestly don’t know, but my best guess is it’s they probably have a policy similar to towing stranded vehicles.
They’ll likely leave them alone, as long as they aren’t causing a major blockage/hazard, provided the owner moves the car ASAP when the roads are once again normally navigable.
Also, a warning, don’t think you are safe parking illegally (blocking a sidewalk)after 6pm in West Seattle. A couple of weeks ago I saw parking enforcement ticket cars in the Uptown Espresso parking lot after 9 pm for blocking the sidewalk.
