Winter Weather Advisory
In short
A weather statement issued by the U.S. National Weather Service to warn of hazardous winter conditions like snow or freezing rain. It is used when precipitation is expected to be problematic but will not reach the high levels required for a formal storm warning.
In plain words
It is a heads-up that winter weather is coming. It means you might face slippery roads or difficult travel conditions. The snow or ice expected is usually not heavy enough to be called a major storm.
A simple example
A local weather office issues an advisory because two inches of snow are expected to fall overnight. This is enough to make driving tricky, but not enough to trigger a blizzard warning.
Why it matters
It helps people prepare for dangerous travel and icy surfaces. It alerts local authorities to be ready for minor disruptions without the extreme urgency of a major blizzard.
Easy to mix up
Do not confuse this with a Winter Storm Warning, which is issued for much heavier and more dangerous accumulations of snow or ice.