The local news is reporting that a winter storm is coming—but is it a winter storm watch, advisory, or warning? Knowing the difference could keep you safe from dangerously cold winds, icy roads, falling tree branches, and the other hazards that come with winter weather.
Storm conditions can change rapidly, so the National Weather Service issues winter storm watches, advisories, and warnings to help guide people on how to prepare for inclement weather. It is part of the same system the agency uses to warn about other weather events, including severe thunderstorms, tornadoes, and flash floods.
The distinctions among these designations can be confusing, however. Here’s what you need to know about what they mean and how to distinguish among them.
Who issues storm watches, advisories, and warnings?
The National Weather Service has more than a hundred local offices across the United States, and each issues winter storm watches, warnings, and advisories for the region that it covers. These designations signal how confident forecasters are that a given area is about to get slammed by a storm, how serious they expect it to be, and what precautions locals should take.
Winter storm watches and advisories, for example, are intended to encouraged preparedness and caution for the possibility of a storm. Winter storm warnings, in comparison, are the most serious of these designations. They indicate that a region is highly likely to see hazardous amounts of snow, sleet, or ice—meaning you should cancel your travel plans.
Importantly, the specific criteria for each of these designations depends on where you live. Regions that are unaccustomed to harsh winter conditions—and therefore are less capable of responding to them—may have a lower threshold for issuing a winter storm warning than a region that’s used to being pummeled by winter weather.
What does a winter storm watch mean?
Winter storm watches are typically the first to be issued when a potentially serious storm is on its way; they are issued between 12 and 48 hours before forecasters expect it to hit. A winter storm watch means that conditions are favorable for a region to see heavy snow, sleet, freezing rain, or other dangerous weather conditions. The National Weather Service may also issue a wind chill watch if there’s potential for cold air and strong winds.
A winter storm watch signals to residents that it’s time to prepare for an oncoming storm. That might mean stocking up on supplies or revising travel plans to make sure you won’t be stranded when the storm hits. Either way, you should pay attention to the news to see whether conditions take a turn for the worse.
What does a winter weather advisory mean?
The National Weather Service issues winter weather advisories to indicate that their forecasters expect the region to get some snow, sleet, or freezing rain—but that it won’t be dangerous enough to merit a warning. Like winter storm warnings, there are different categories of advisories, including wind-chill advisories and lake effect snow advisories.
Even though they may indicate milder conditions, winter weather advisories are no time for slouching: These conditions could threaten your life or property if you don’t exercise caution. Watch out for slick roads and snow showers that will make travel more challenging. And, in a wind-chill advisory, make sure to wear warm layers if you need to go outdoors.
What does a winter storm warning mean?
When local forecasters are more confident that severe weather conditions are in the cards, they may upgrade a winter storm watch to a winter storm warning. This typically happens about 12 to 24 hours before the storm is expected.
Winter storm warnings indicate the arrival of heavy snow, sleet, or freezing rain that could be a significant threat to the region. They’re a signal that it’s not safe to travel or go outside. Instead, the National Weather Service recommends taking action to protect yourself by delaying travel plans until conditions improve or taking shelter if you’re already exposed.
In addition to winter storm warnings, there are also different categories of winter weather-related warnings: For instance, forecasters may issue a blizzard warning if they expect gusts of snow greater than or equal to 35 miles an hour that will significantly reduce visibility for at least three hours. If you get stranded in your car during a blizzard warning, authorities recommend staying put and waiting for help.
Ice storm warnings indicate the likelihood of at least a quarter inch of ice, raising the chances of snapped power lines and tree branches and impassable roads. Wind chill warnings signal that temperatures are expected to drop to levels that could cause frostbite or hypothermia within several minutes of exposure. Some regions also receive warnings for heavy but narrow bands of lake-effect snow that can cause sudden restrictions in visibility.