Watch vs. warning vs. advisory – what’s the difference?
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Reprinted from CNYCentral.com by Wayne Mahar, March 17, 2009
Severe Thunderstorm Warning, Tornado Watch, Lake Effect Snow Warning, Wind Advisory, Freezing Rain Advisory| we TMve heard all of these before and will hear them again. So which of these should have us taking life saving measures and which should we all but ignore? Well, a lot of the time it comes down to whether it is an Advisory, a Watch or a Warning.
No matter what the actual weather you are dealing is, here is the basic rule of thumb:
WATCH essentially means a chance this condition will happen and usually covers a large geographical area for a lengthy time period.
WARNING means the said weather is already occurring or is likely to occur and to take proper protective measures. Warnings are usually issued for much smaller geographical areas and usually for shorter more definite time periods.
ADVISORIES are sort of in between a WATCH and WARNING. The expected weather condition has a pretty good chance of occurring, even a likely chance of occurring, but typically an advisory is used for less severe type of weather conditions. A Wind Advisory might be issued or a Freezing Rain Advisory issued instead of a High Wind Warning or an ice Storm Warning.
Yes, it can get confusing, even to us as meteorologists. There are a multitude of advisories, watches and warnings, all of which were developed by the good folks at the National Weather Service. Below I am listing mainly winter terms courtesy of the National Weather Service. It is likely you won TMt remember what each means. If so, simply try to keep in mind what we already talked about.
1) WINTER STORM OUTLOOK
This is a statement issued when there is a chance of a major winter storms from 3 to 5 days in the future. This is meant to assist people with their long range plans. However, since the outlook is issued so far in advance, the accuracy of the prediction may be limited.
2) WINTER STORM WATCH
This means there may be hazardous winter weather due to various elements such as heavy snow, sleet, or ice accumulation from freezing rain. In our region, heavy snow means 7 inches or more of accumulation in 24 hours or less. A “WATCH” is a long range prediction. They are issued at least 12 hours before the hazardous winter weather is expected to begin. When the storm becomes imminent, or has a high probability of occurring, the watch will be upgraded to a “WARNING”.
3) WINTER STORM WARNING FOR HEAVY SNOW
Seven inches or more of snow will fall within a 24 hour period.
4) WINTER STORM WARNING FOR SEVERE ICING
Heavy accumulation of ice due to freezing rain will down trees and power lines. Electricity, or telephone communications, may be out for a long period of time. Roads may become impassable for most vehicles.
5) BLIZZARD WARNING
This is issued for a combination of strong winds averaging or frequently gusting to, or above, 35 miles an hour and very low visibility due to blowing or falling snow. These are the most dangerous winter storms and can be especially severe when combined with temperatures below 10 degrees.
6) WINTER STORM WARNING
This is issued when a dangerous combination of heavy snow, with sleet and/or freezing rain, will occur or has a high probability of occurring within the next 12 hours.
7) HIGH WIND WARNING
This means the expected winds will average 40 miles an hour or more for at least 1 hour or winds gusts will be greater than 58 miles an hour. Trees and power lines can be blown down. A High Wind Warning may be preceded by a HIGH WIND WATCH if the strong winds are not expected to occur for at least 12 hours.
8) WIND CHILL WARNING
This means life threatening cold with wind chill temperatures computed to be -40 degrees or less for at least 3 hours. Exposure to this combination of strong winds and low temperatures without protective clothing will quickly lead to frostbite and/or hypothermia. Longer exposures can be fatal.
9) WINTER WEATHER ADVISORY FOR SNOW
This is issued for snowfall greater than 4 (but less than 7) inches in a 24 hour period. The snowfall is usually expected to begin within the next 12 hours.
10) BLOWING SNOW ADVISORY
This is issued when the visibility will be significantly reduced, or when the roads become snow covered over a large area.
11) WIND CHILL ADVISORY
This is issued for cold temperatures and winds, with wind chill temperatures computed to be -25 degrees or less for at least 3 hours. Exposure to this combination of strong winds and low temperatures without protective clothing can lead to frostbite and/or hypothermia, Prolonged exposure may be fatal.
12) WINTER WEATHER ADVISORY
This is issued for a combination of snow, sleet, and/or freezing rain. Advisories, in general, are issued for weather conditions that are expected to cause significant inconveniences and may be hazardous, These situations are normally not life threatening if caution is exercised.
13) WIND ADVISORY
This is issued for average wind speeds between 31 and 39 miles an hour, or for frequent wind gusts between 46 and 57 miles an hour.