West of Plymouth the subdivisions thin out into open ground toward Salem, and that is where a winter wind gets its running start. Air Side Snow works the hours nobody volunteers for — plowing driveways and lots, clearing walks and steps, laying salt while the streetlights are still the brightest thing on the block. A clipper can drop three inches between the late news and the alarm clock, and the answer is a clean pass down to pavement before the first car backs out. There is a real satisfaction in a drive that looks like the storm simply skipped that address. Snow is the entire assignment here, from the first dusting in November to the stubborn March squalls.