Winter storm watch

A Winter Storm Watch is issued by the National Weather Service of the United States when there is a potential for heavy snow or significant ice accumulations. The watch is usually issued 12 to 48 hours before the storm's arrival in the area. As is true with a Winter Weather Advisory, the criteria for this watch can vary from place to place. If strong winds are expected with reduced visibilities, a winter storm watch may be upgraded to a Blizzard Watch. A Winter Storm Watch is different from a Winter Weather Advisory in the sense that a Winter Weather Advisory is meant to advise those of the conditions that currently exist outside, while a Winter Storm Watch simply means that there is a chance of a storm coming. A Winter Storm Watch will become a Winter Storm Warning when the storm is in happening or about to happen. Winter Storm Watches are given so that communities can prepare in the chance that the winter storm does in fact hit. Winter storm watches often go in place when there is a chance between 50-80% of the storm occurring.

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Wikipedia