According to the National Weather Service, winter weather-related Warnings, Watches, and Advisories are issued by your local National Weather Service office. Each office knows the local area and will issue Warnings, Watches, or Advisories based on local criteria. For example, the amount of snow that triggers a “Winter Storm Warning” in the Northern Plains is typically much higher than the amount needed to trigger a “Winter Storm Warning” in the Southeast.
A warning means you need to take action.
A watch means you should be prepared.
An advisory means you should be aware.
Here's a graphic that explains it in terms that all Marylanders can understand!
A Code Blue Extreme Cold alert means temperatures, including wind chill, are expected to be extremely cold and pose particular danger for certain vulnerable populations. Though all area residents who are subject to a Code Blue Extreme Cold alert are encouraged to take precautions to ensure warmth, the alert triggers additional response effort and services, particularly for the homeless and seniors.
For more information about winter weather warnings, watches, and advisories, visit https://www.weather.gov/safety/winter-ww.