Precipitation types the preceding adjective "freezing", becoming known as freezing rain or freezing drizzle. Frozen forms of precipitation include snow, ice needles, sleet, hail, and graupel. Their respective intensities are classified either by rate of fall, or by visibility restriction. Precipitation falls in many forms, or phases. They can be subdivided into: The parenthesized letters are the METAR codes for each phenomenon. Precipitation occurs when local air becomes saturated with water vapor, and can no longer maintain the level of water vapor in gaseous form. This occurs when less dense moist air cools, usually when an airmass rises through the atmosphere. However,
Winter weather advisory Snow Advisory, specific for when snow and blowing snow were the only hazards expected in the advised area. The Winter Weather Advisories for Snow, for Sleet, for Blowing Snow, and for Snow and Blowing Snow, respectively, have since replaced them. Because of the changes with the 2008-09 winter storm season, several varieties have been noted throughout the US. Also to be noted: Winter weather advisory A Winter Weather Advisory is issued by the National Weather Service of the United States when a low pressure system produces a combination of winter weather (snow, freezing rain, or sleet) that presents a hazard,