Winter storms can trigger warnings, watches and advisories. What do they all mean?
For millions of us, winter weather has already started. As the winds howl, the snow flies and the temperatures drop, the National Weather Service issues various levels of alerts for wintry weather.
While some sound similar, each alert issued by local National Weather Service offices signals different winter conditions. Each office knows the local area and will issue warnings, watches or advisories based on criteria which vary from office to office.
For example, the amount of snow that triggers a winter storm warning in the northern Plains is typically much higher than the amount needed to trigger a similar winter storm warning in the Southeast.
Other non-storm related alerts include freeze and frost watches and warnings, and wind chill warnings.
Afraid of hypothermia, icy roads? How to stay safe during snow storms.
Here's what winter weather alert terms mean:
What is a winter weather advisory?
A winter weather advisory is issued when snow, blowing snow, ice, sleet, or a combination of these wintry elements is expected, but conditions should not be hazardous enough to meet warning criteria. Be prepared for winter driving conditions and possible travel difficulties. Use caution when driving.
Map: United States Weather Alerts
What is a winter storm watch?
A winter storm watch is issued when there is the potential for significant and hazardous winter weather within 48 hours. It does not mean that significant and hazardous winter weather will occur ‒ it only means it is possible. It's issued when dangerous winter weather such as a blizzard, heavy snow, significant freezing rain or heavy sleet is forecast. Usually it is issued 12 to 36 hours in advance of the winter weather.
What is a winter storm warning?
A winter storm warning is issued for a significant winter weather event including snow, ice, sleet or blowing snow or a combination of these hazards. Travel will become difficult or impossible in some situations. Delay your travel plans until conditions improve. Usually it is issued 6 to 18 hours in advance of the winter weather.
What is a blizzard warning?
A blizzard warning lets you know that snow and strong winds will combine to produce a blinding snow (near zero visibility), deep drifts, and life-threatening wind chill. Specifically, it is issued when sustained or gusty winds of 35 mph or more are expected to reduce visibility at or below a quarter-of-a-mile due to falling and/or blowing snow for at least three hours.
What is a lake-effect snow warning?
A lake-effect snow warning is issued when pure lake-effect snow (when the snow is a direct result of lake effect snow and not because of a synoptic storm or low pressure system) may pose a hazard or it is life threatening.
What is a snow squall warning?
A snow squall warning is issued when a snow squall is in the forecast. A snow squall is an intense, but limited duration, period of moderate to heavy snowfall, accompanied by strong, gusty winds and possibly lightning (generally moderate to heavy snow showers). Snow accumulation may be significant.
What is an ice storm warning?
An ice storm warning is issued when ice accumulation of at least 1/4 inch is expected.
This article originally appeared on USA TODAY: Warnings, watches and advisories: Winter weather alerts explained
