Watch, Warning, and Advisory Definitions

Winter Weather Definitions

For watches and warnings:

Blizzard
Visibility frequently below 1/4 mile in falling or blowing snow, and wind speeds (sustained or frequent gusts) at least 35 mph. These conditions are expected to continue for 3 hours or longer.
Winter Storm
A snow accumulation of at least 5 inches in 6 hours, in combination with one of the following: rain, freezing rain, sleet, wind, blowing snow or cold (wind chill).

(Note: lesser amount of snow can be forecast for mixed precipitation, blowing, etc.)

Lake Effect Snow
A pure lake effect snow event that is forecast to produce a snow accumulation of at least 4 inches in 6 hours, or at least 5 inches in 9 hours, or at least 6 inches in 12 hours, or at least 7 inches in 18 hours and 8 inches or more in 24 hours.

(Note: lesser amount of snow can be forecast for mixed precipitation, blowing, etc.)

Ice Storm
A significant, and possibly damaging, accumulation of ice. Normally a coating of at least 1/4-inch, but may be up to 1/2-inch if winds are less than 15 mph.
Heavy Snow
A snow accumulation of at least 5 inches in 6 hours. Heavy snow accumulations are the only hazard expected.
Sleet
An accumulation of sleet of at least 1/2-inch.

For warnings only:

Wind Chill
Wind chill values fall to -25°F or colder.

For advisories:

Snow
Synoptic scale storm producing snow (average forecast range) of greater than 2 inches in 6 hours, or at least 4 inches but less than 6 inches in 12 hours, or at least 4 inches in 12 hours but less than 8 inches.

(Note: lesser amount of snow can be forecast for first snowfall, long duration between snow, etc.)

Snow and Blowing/Drifting Snow
Situations that cause significant inconveniences, and do not meet warning criteria. Sustained wind or frequent gusts of 25 to 34 mph accompanied by falling and blowing snow, occasionally reducing visibility to less than 1 mile for three hours or more. If caution is not exercised, this could lead to life-threatening situations.
Freezing Rain or Freezing Drizzle
Situations that cause significant inconveniences, and do not meet warning criteria. If caution is not used, this could lead to life-threatening situations. Ice accumulation causes driving or walking problems, but no damage to trees or power lines.
Lake Effect Snow
Pure lake effect snow event that is forecast to produce snow (average of forecast range) of greater than 2 inches in 6 hours, or at least 4 inches but less than 6 inches in 12 hours, or at least 4 inches in 12 hours but less than 8 inches.
Winter Weather
A synoptic scale storm producing a combination of winter weather that presents a hazard, and does not meet warning criteria. Snowfall in this case does not have to reach snow advisory criteria.
Wind Chill
Wind chill values drop between -15 and -24°F inclusive.
Blowing Snow
Blowing snow reducing visibilities to 1 mile or less and winds less than 35 mph.
Sleet Advisory
Situations that cause significant inconveniences, and do not meet warning criteria. If caution is not used, this could lead to life-threatening situations. Ice accumulation causes driving or walking problems, but no damage to trees or power lines.

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