KANSAS CITY, Missouri - NBC Action News Meteorologist Brett Anthony explains winter weather meteorology terms to help us all understand the forecast.
For starters, there are four basic categories into which most winter weather falls:
Hazardous Weather Outlook is issued when there is a threat of hazardous weather in the next seven days. Since predicting the timing and specific characteristics of some weather events can be uncertain, this kind of alert can let viewers know they should be prepared for potentially threatening weather.
Watch is more immediate, and is issued 12 to 48 hours in advance of an impending weather event. Though it’s still not exact, it lets the viewers know that it might be a good idea to reschedule appointments, change dinner plans, and stock up on whatever supplies might be low. Potentially damaging and dangerous weather is headed in!
An Advisory is even more urgent. You hear these during the snowiest times of winter, because they refer to an event that is either going to happen in the next 12 hours, or is occurring already. Caution should be taken, and your commute might take longer than usual—in fact, you should probably avoid unnecessary travel, just to be safe—but most daily activities can still go on. Whatever happens, it’s not likely to be life-threatening.
The fourth type of alert is the most urgent of all, a Warning. Like an Advisory, it refers to an event coming up in the next 12 hours, or that’s going on right now. However, when a Warning is issued it means that there is a significant threat to life, property, and livestock. Routine activities should be canceled, and travel is definitely not recommended.
That covers the four general terms, but that’s hardly everything you need to know. Specific weather events, of which there are several possible, can be qualified as either an advisory or a warning, depending on specific circumstances. (A Watch is still just a Watch, no matter what type of event is predicted.)
For instance, in order for a Heavy Snow Warning to be issued, the snow must be expected to reach 6 inches or more within 12 hours, or 8 inches within 24 hours. Two to five inches in 12 hours would only qualify as a Snow Advisory.
A Wind Chill Advisory is issued when wind chill reaches, or is expected to reach, 20- to 39- degrees below zero, with 10 mph or higher winds. However, if it’s expected to reach 40-below or colder, then a Wind Chill Warning is issued.
Basically, whatever an Advisory is, a Warning is that much worse.
Some Advisories don’t have corresponding Warnings, though, and vice versa.
For example, there’s a Blowing Snow Advisory when snow is causing visibility to be restricted to less than half mile. But there’s no such thing as a Blowing Snow Warning. When visibility is or will be less than a quarter mile, for three hours or more, with sustained winds or gusts get up to 35 m.p.h., that’s called a Blizzard Warning.
Ice and sleet can be a terrible inconvenience, even a danger. An Ice Storm Warning is issued when ice accumulates to a quarter of an inch or more. But anything less than that and it’s not an Ice Storm Advisory; it becomes a Freezing Rain Advisory.
And as for that more ominous-sounding Winter Weather Warning—or Advisory - that’s what happens when more than one predominant type of weather event (e.g. blizzard and wind chill, or snow and blowing snow) occurs together, and at least one of them meets either advisory or warning criteria.
If you want to dig even deeper, you can find all kinds of useful facts and safety tips at the National Weather Service website.