I don't know if this ski resort is using this ad scheme again this year (although I hope they are, especially considering how much they probably cost), but these are from last year.
They're not just snowing signs either. When weather conditions reach their optimum levels (wee, snow!), an SMS message is delivered to the billboards that tells them to start "snowing." This alerts passersby that they should "ditch work," as Gizmodo says, to go skiing instead.