Winter Watch, Warning and Advisory Definitions

• Recent Watches/Warnings/Advisories for Southeast Michigan

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

Generally defined as a snow accumulation of at least...

• • 8 inches or more in 12+ hours
  • 6 inches or more in 6 to 9 hours

Can be 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 ...

• • • 8 inches or more in 12+ hours
    • 6 inches or more in 6 to 9 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.

For warnings only:

Wind Chill

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

For advisories:

Winter Weather Advisories for...

• Snow

Synoptic scale storm producing snow (average forecast range) of greater than 3 inches in 6 hours, or at least 4 inches but less than warning snowfall.

(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.

• 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.

• 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.

• 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 3 inches in 6 hours, or at least 4 inches but less than warning snowfall.

• Wind Chill

Wind chill values drop between -15 and -24°F inclusive.