Winter weather advisory
A winter weather advisory (originally identified as a Traveler's Advisory until the 2002-03 climatological winter when officially renamed, and informally as such by some local television stations thereafter) is a hazardous weather statement issued by local Weather Forecast Offices (WFO) of the National Weather Service in the United States when one or more types of winter precipitation—snow, rain and snow mixed, freezing rain, sleet, graupel, etc.—presenting a hazard, but not expected to produce accumulations meeting storm warning criteria (usually below four inches (10 cm)), are forecast within 36 hours of the expected onset of precipitation or are occurring in the advisory's coverage area. == Definition == In the United States, the criteria necessary to issue a Winter Weather Advisory is defined by each local NWS Weather Forecast Office, and is based on the climatological impact of frozen precipitation on travel and commerce within the specified region.