Since it is winter in the Northern Hemisphere, we thought it would be a good idea to explain a little bit about the variety of winter weather watches, warnings and advisories. During these cold months, you’ll probably hear some of these terms in the weather forecast, but we will give you a better idea of just what they mean.
The first thing to keep in mind, is that the National Weather Service sets its watch, warning and advisory criteria depending on location or region. For example, snow in New York City is not as big a deal as it would be in a city in the south, where bad winter weather conditions are less frequent. This mostly has to do with what are considered typical types of winter weather for a specific area, and what people are accustomed to dealing with. While 3 inches of snow in New York might be a nuisance, 3 inches of snow in Dallas or Atlanta might cause much bigger problems because people there may not be used to that kind of weather.
Watches and Warnings are issued by National Weather Service regional offices, and they go by county, and usually cover a wide area, often including several states.
Here are a couple of watches and warnings you will hear a lot over the winter, if you live in a snow-prone area: Winter Storm Watches, and Warnings. The difference between a Watch and a Warning is straightforward. A Watch means conditions are favorable for dangerous weather conditions. A warning means winter storm conditions are imminent or occurring.
First off, here’s the NWS definition of a “winter storm”: 5 inches or more of snow or sleet in a 12 hour period, or 7 inches or more of snow or sleet over a 24 hour period. There are a few other elements that could come into play, like enough ice accumulation, mainly freezing rain, to cause damage to trees and power lines, or a life-threatening or damaging combination of snow and ice, with gusty wind.
Now here are a few you might not be familiar with. For example, an “Ice Storm Warning”. Those aren’t much fun, and they’re issued when a quarter inch or more of ice accumulation is expected. Usually, that will be freezing rain, which is precipitation that falls as liquid, and freezes when it hits the surface. A quarter inch of ice is heavy enough to cause tree damage and power outages, not to mention very hazardous driving and walking conditions.
You have probably heard the term “Blizzard Warning”. So, what exactly is that? A Blizzard Warning is a bit different from a Winter Storm Warning, mainly because focuses more on wind and visibility. Basically, winds of 35 mph or greater, and visibility of a quarter-mile or less, constitute a Blizzard Warning.
There is a prevalent misconception that a Blizzard Warning means it will be extremely cold, or there will be heavy snowfall. However, there is no temperature requirement for a Blizzard Warning, and snow does not actually have to be falling. Snow that is already on the ground, combined with the wind, could meet the low visibility requirements for a Blizzard Warning.
The next one does have to do with cold, and that is a “Wind Chill Warning”. It means wind chill temperatures of minus 25 degrees or lower are expected in the next 12 to 36 hours. During a Wind Chill Warning, you should either stay in a warm place, or have the right type of clothing to protect yourself completely against the cold. Even though it may be sunny, wind chill can cause frostbite on exposed skin, and possibly hypothermia, quite quickly.
Those are the biggies. Now, you might hear the word “Advisory” associated with hazardous winter weather. That means the dangerous winter conditions we talked about are likely, but not bad enough to meet the criteria for a warning. But that does not mean it won’t be dangerous. And again, that depends on where you are located. An advisory for snow in New York might qualify as a warning for a place like Atlanta.
This is a lot to remember. But when you hear the words “watch”, “warning” or “advisory” in a winter weather forecast, you should pay close attention to the forecast so you’ll know what to expect and figure out how the conditions will affect your situation.
Always have enough food, water, medicine, protective clothing on hand, and a well-maintained vehicle to get you through any weather trouble.
The National Weather Service website has all of this detailed out, including current maps showing you where the rough spots are.
Sources:
National Oceanic and Atmospheric Administration / National Weather Service
