Winter Weather Advisory, Watch and Warning Criteria Explained

A lot of confusion results from the criteria that triggers the various types of winter weather advisories, watches and warnings. We have to remember that…

A WATCH for winter weather means that there is the potential for hazardous wintry conditions to occur within the next 24 to 72 hours

A WARNING means hazardous winter conditions are either occurring or will occur within the next 24 hours

An ADVISORY can be issued at anytime, and means you need to be aware of your surrounding weather conditions.

Here are how the National Weather Service office in Birmingham defines each one…

Winter Storm Watch
Issued when conditions are favorable for hazardous winter weather conditions to develop within the next 12 to 48 hours. A Winter Storm Watch is issued when one or more of the following is expected:
…Snowfall of 2 inches or greater
…Freezing rain/drizzle (ice) accumulations greater than or equal to 1/4 inch
…Sleet (ice pellets) accumulations 1/2 inch or greater

Winter Weather Advisory
Issued for a winter weather event that causes significant inconveniences, doesn’t meet warning criteria, but can still be life threatening if caution is not exercised. A Winter Weather Advisory is issued if more than one type of hazardous winter weather is expected, is occurring, or is imminent:
…Sleet (ice pellets) accumulations of less than 1/2 inch
…Freezing rain/drizzle (ice) accumulations less than 1/4 inch
…Snowfall accumulations of 1/4 inch to 2 inches (A dusting of snow does not require an advisory)

Winter Storm Warning
Issued when a combination of hazardous winter weather is at or less than 24 hours from occurring. Winter Storm Warnings are issued when one or more of the following is expected:
…Snowfall of 2 inches or greater
…Freezing rain/drizzle (ice) accumulations greater than or equal to 1/4 inch
…Sleet (ice pellets) accumulations 1/2 inch or greater

Blizzard Warning
Same as a Winter Storm Warning, but has the added criteria of:
…Sustained wind or frequent gusts of 35 MPH or greater
…Falling and/or blowing snow reducing visibilities to less than 1/4 mile
…Lasts for three hours or longer

Freezing Rain Advisory
Issued when freezing rain is forecast to produce ice accumulations of less than 1/4 inch.

Ice Storm Warning
Issued when freezing rain is forecast to produce a significant and perhaps damaging amount of ice, with accumulations of 1/4 inch or more.

Hard Freeze Watch
Issued when ambient temperatures are expected to be less than 27F for more than 2 hours in a 12 hour period. Generally issued within 24 to 48 hours of event occurrence.

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Category: ALL POSTS, Winter Weather