Watch and Warning Definitions:
Watch
A "Watch" indicates a higher probability of the development
of severe weather. Severe Thunderstorm or Tornado Watches are issued by
the NOAA's Storm Prediction Center in Norman, Oklahoma for multiple counties
or states for about six hours.
Warning
A "Warning" indicates severe weather is imminent or occurring.
Warnings are issued by local National Weather Service offices based on
Doppler radar reflectivity or storm spotter reports. A typical tornado
or severe thunderstorm warning is issued for one or two counties for a
period of less than one hour.
Here
are some of the more common Advisories, Watches and Warnings issued by
NWS:
Wind
Advisory
- Sustained winds of 25 - 39 mph or gusts up to 57 mph
High Wind Watch
- Expected sustained winds of up to 40 mph, or
- Wind gusts exceeding 57 mph
High Wind Warning
- Sustained winds of up to 40 mph, or
- Wind gusts in excess of 57 mph
- Caution should be taken when driving high-profile vehicles
Wind Chill Advisory
- Wind chill temperatures of -30 F to -35 F or below
Flash-Flood Watch
- Heavy rains that may result in flash-flooding in the specified area
- Be alert and prepared for the possibility of a flash-flood emergency
requiring immediate action
Flash-Flood Warning
- Flash-flooding is occurring or is imminent in the specified area
- Move to a safe area immediately
Severe Thunderstorm Watch
- Conditions favorable for thunderstorms with:
- Winds in excess of 57 mph and
- 0.75
(3/4) inch or greater diameter hail
Severe Thunderstorm Watches are issued by the Storm Prediction Center
in Norman, Oklahoma. They usually cover large parts of states or multiple
states for a period of six hours or more.
Severe Thunderstorm Warning
Severe thunderstorms have been confirmed by radar and/or sighted by spotters.
- Large Hail (3/4 inch diameter or greater)
- Damaging Winds (58 mph or greater)
Tornado Watch
Conditions favorable for tornado development in a specified area during
a specified time period.
Tornado Watches are issued by the Storm Prediction Center in Norman, Oklahoma.
They cover large parts of states, or multiple states for a period of six
hours.
Tornado Warning
Tornadoes have been confirmed by radar and/or sighted by spotters.
Snow Advisory
- Snowfall of 2" or more in 12 hours or
- Snowfall of 3" or more in 24 hours
Keep in mind that "Snowfall" is not the same as "Snow Depth".
Snowfall is the actual amount of snow that has fallen, not including
melting or compression. Snow depth is the actual amount of snow on the
ground, including melting and compression. Snow advisories are
usually issued for non-mountainous areas.
Winter Storm Warning
- Snowfall of 4" or more in 12 hours or
- Snowfall of 6" or more in 24 hours
In areas where snowfall is less frequent, a Winter Storm Warning may be
issued for lesser amounts.
Blizzard Warning
- Winds of 35 mph or greater
- Falling or blowing snow
- Visibility of less than 1/4 mile
Dense Fog Advisory
- Visibility of less than 1/4 mile
In fog-prone areas, a Dense Fog Advisory may be issued when visibility
is less than 1/8 mile.
Hurricane Watch
Issued when a hurricane or tropical storm is expected to threaten coastal
areas in the next 24 - 48 hours. Be prepared to take action.
Hurricane Warning
- A hurricane or tropical storm is expected to make landfall in the specified
area in the next 24 hours.
- Wind speeds in excess of 74 mph (64 knots)
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