This post may be like when you notice a new painting or haircut and the person you notice this to says that’s not new I bought this painting three years ago or cut my hair this way six months ago but

In the lead up to this week’s snow storm, I noticed the phrase “6 inches of plowable snow.” I immediately googled and found the definition capable of being plowed.

This redundant definition did not answer my questions. What is the difference between plowable snow and unplowable snow?  How can the Weather Service know that the snow will be plowable till somebody tries to plow it? Another person that I posed  this question to asked if plowable snow meant that you couldn’t claim a snow day because the snow was plowable and therefore driveable.

Can someone  help me out?