When late fall and winter roll around, weather warnings come fast and furious. But there's so many different ones that have specific meaning to the National Weather Service, but might leave you at home scratching your head. Like: What's the difference between a Snow Advisory and Winter Storm Warning?
To start with the basics: a "Watch" means conditions are favorable for the highlighted event, but not certain yet. These typically get issued 12-48 hours in advance of an approaching event. Sort of like a "heads up." A "Warning" means conditions are imminent within 12 hours or are already occurring.
Let's break down some of the most common ones we see around Western Washington this time of year:
High Wind Warning: -- Issued when wind speeds of sustained 40 mph with gusts to 58 mph are occurring or imminent.
High Wind Watch: -- Issued when potential exists for wind speeds of sustained 40 mph with gusts to 58 mph, but timing and location of storm are not certain.
Wind Advisory: -- Sustained winds of 30-39 mph or gusts of 45-57 mph are expected or occurring.
Flood Watch: -- This means flooding is possible within 48 hours. These are issued by county and cover all rivers inside the county in question.
Flood Warning: -- These are issued by individual river and mean flooding is imminent or occurring.
Urban and Small Stream Flood Advisory: -- Localized flooding from heavy rain in city or rural areas. Typically non-life threatening.
Heavy Snow Warning: -- For the mountains above 2,000 feet, this is 12" of snow or more in 12 hours, or 18"+ in 24 hours. For the lowlands, it's 4" or more in 12 hours or 6" or more in 18 hours.
Winter Storm Warning: -- Conditions for Heavy Snow Warning plus added element of wind or other hazard.
Winter Storm Watch: -- Warning-like conditions possible with the next 12-48 hours.
Snow Advisory: -- For the mountains, it's 6-11" in 12 hours or 11-17" in 24 hours. For the lowlands, it's 1-3" in 12 hours or 3-5 inches in 24 hours. (Sometimes this also comes out as a "Winter Weather Advisory" -- that might mean it could be sleet or freezing rain too)
Severe Thunderstorm Warning: -- Thunderstorm with 58 mph winds and/or large hail are occurring or imminent.
Tornado Warning: -- Tornado spotted on the ground or indicated by radar.
(Severe Thunderstorm and Tornado Watches have never been issued here)
Sometimes a "Significant Weather Advisory" is issued for strong thunderstorms that don't quite meet the criteria of a "severe thunderstorm" but warrant attention nonetheless.
You can read more at the National Weather Service site