WSET.com - ABC13Watches, Warnings, Advisories, Oh my! by Sean Sublette

What do all those things mean anyway?  

Watches, Warnings, and Advisories are the three levels of alerts sent by the National Weather Service when threatening weather is expected.  Threatening weather is defined as weather that poses a threat to life and/or property.

An Advisory is the lowest threat level.  It means the weather parameter expected (High Winds, Dense Fog, Freezing rain, etc.) is likely to cause minor problems, but with the appropriate precautions, only small inconveniences should result.

A Watch means conditions are favorable for the development of threatening weather.  That means the threatening weather is not here yet, but there's a good chance it is coming soon. You can think of it as a code yellow. 

A Watch also means it is time to start thinking about what you would do if the threatening weather materializes.  For example, a Tornado Watch means that the conditions are coming together in such a way that the development of tornadoes is a strong possibility in the coming few hours.  Severe Thunderstorm Watches work the same way.

Although Flood Watches and Winter Storm Watches also mean conditions are favorable for development of those phenomena, those types of hazards take longer to develop than severe thunderstorms and tornadoes.  As a result, Flood Watches and Winter Storm Watches tend to be issued 12-24 hours ahead of time.

A Warning means that the expected weather hazard is either happening or about to happen. Whatever plan you came up with to keep safe, it is time to put it into action.  It is more analogous to a code red.

In the case of a Severe Thunderstorm, Tornado, or Flash Flood Warning, the threat has either already materialized or will be starting within the next 30 minutes.  Winter storms tend to build more slowly than tornadoes, severe thunderstorms, and flash floods.  So their Warnings tend to come a few hours before the threatening weather begins.

Our local National Weather Service Office, located on the campus of Virginia Tech, issues most of these alerts (aka products), and you can find their specific definitions at the link below.  It is a great reference site.

http://www.erh.noaa.gov/rnk/product_guide.htm

There are two products, however, that originate away from the local National Weather Service Office:  Severe Thunderstorm Watches and Tornado Watches, which are issued from the Storm Prediction Center in Norman, Oklahoma.  Norman was chosen because of its close ties to the University of Oklahoma, which, for all intents and purposes, is the Severe Weather Research Capital of the United States.  Their link is below:

http://www.spc.noaa.gov/products/