The difference between Winter Weather Advisories, Winter Storm Watches and Warnings

Weather

There are many watches and warnings issued in the world of Meteorology, but what are the main differences between Winter Weather Advisories, Winter Storm Watches, and Warnings?

The National Weather Service has set guidelines for when certain weather alerts will be issued across the region.

Firstly, the differences between an advisory, watch and warning are simple.

A watch is essentially a chance for certain conditions to happen. A warning means the said weather event is already occurring or is likely to occur and to take proper precautions. Advisories are in between a watch and warning, stating the expected weather conditions have a good chance of occurring, but usually, an advisory is used for less severe types of weather.

The specific criteria for Winter Storm Watches, Warnings and Winter Weather Advisories are developed by the National Weather Service (NWS) and are listed below:

Winter Storm Watches: 

Means conditions are favorable for a winter storm event (heavy sleet, heavy snow, ice storm, heavy snow and blowing snow or a combination of events) to meet or exceed local winter storm warning criteria in the next 24 to 72 hours. Criteria for snow is 7 inches or more in 12 hours or less; or 9 inches or more in 24 hours covering at least 50 percent of the zone or encompassing most of the population. Use “mid-point” of snowfall range to trigger a watch. Criteria for ice is 1/2 inch or more over at least 50 percent of the zone or encompassing most of the population. This includes lake effect snow.

Winter Storm Warnings:

Means a winter storm event is expected to meet or exceed local winter storm warning criteria in the next 12 to 36 hours. Criteria for snow is 7 inches or more in 12 hours or less; or 9 inches or more in 24 hours covering at least 50 percent of the zone or encompassing most of the population. Use “mid-point” of snowfall range to trigger warning. Criteria for ice is 1/2 inch or more over at least 50 percent of the zone or encompassing most of the population.

Winter Weather Advisories:

Meaning a winter storm event is expected to meet or exceed local winter weather advisory criteria in the next 12 to 36 hours but stay below warning criteria. Criteria for snow is 4 inches or more in 12 hours or less covering at least 50 percent of the zone or encompassing most of the population. Use “mid-point” of snowfall range to trigger advisory. Criteria for ice is any ice accumulation less than 1/2 inch over at least 50 percent of the zone or encompassing most of the population. Winter Weather Advisory can also be issued for black ice. This is optional.

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