A winter storm watch is issued by the National Weather Service of the United States when there is a possibility of heavy snow or potential of significant ice accumulations, without meeting a specific other winter criteria.
The watch is typically issued 12 to 48 hours before the storm's expected arrival in the given area.
[citation needed] As the event of the storm draws nearer in time and confidence in the occurrence of significant winter weather conditions and accumulation is increased, the weather watch will be upgraded to a winter storm warning or blizzard warning, depending on whether blizzard conditions will be met.
A watch could be discontinued altogether if neither warning nor advisory-level conditions are expected to be met and when the possibility of a winter storm fades.
[2][3] Watches generally go into effect when the chance of meeting warning criteria ranges from 50% to 80% of snow.