NWS Winter Weather Warning Criteria

Now that we’re approaching the winter season, it’s time to refresh what criteria are necessary for winter weather headlines in our area. Below is the official criteria for winter weather headlines from the National Weather Service office in Pittsburgh:

WINTER WEATHER ADVISORY
Snow accumulations of 3 inches over 12 hours; Any freezing rain accumulations less than ¼ inch; Or a high impact snow/ice event.

WIND CHILL ADVISORY
Issued when wind chill -10ºF to -25ºF for at least 3 hours are expected.

WINTER STORM WATCH
Potential for a blizzard, heavy snowfall, or ice storm within the next 18 to 48 hours; Issued when there is a 50% confidence or greater of at least 6 inches of snow over 12 hours, or at least 8 inches of snow over 24 hours, and/or a ¼ inch of ice.

WIND CHILL WATCH
Issued when wind chills of -25ºF or colder with wind speeds 5 mph or greater for at least 3 hours within the next 18 to 48 hours.

WINTER STORM WARNING
Snow accumulations 6 inches or greater in 12 hours (8 inches or more in 24 hours); Freezing rain accumulations ¼ inch or greater.

BLIZZARD WARNING
Sustained winds 35 mph or greater AND falling/blowing snow reducing visibility to less than ¼ mile for at least three hours.

ICE STORM WARNING
Freezing rain accumulations ¼ inch or greater resulting in significant, widespread power outages, tree damage, and dangerous travel.

LAKE EFFECT SNOW WARNING
Lake effect snow accumulations 6 inches or greater in 12 hours (8 inches or more in 24 hours). This is issued only for the northernmost portions of our area.

SNOW SQUALL WARNING
A short-duration (less than 1 hour), polygon-based warning issued when strong snow squalls and flash freezing will cause dangerous and life-threatening conditions, especially for roadways. Usually issued when ground/road temperatures are sub-freezing and visibility is less than ¼ mile.

WIND CHILL WARNING
Wind chill of -25ºF or colder with wind speeds 5 mph or greater for at least 3 hours.

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