Ohio Winter Safety Week 2009

Winter Weather Forecast Terminology

Photo copyright University Corporation for Atmospheric Research. Used with permission.

Common Winter Weather Events

• Freezing Rain: Rain that freezes upon contact with a cold surface.
• Sleet: Solid grains of ice that form from rain that freezes before reaching the ground. These pellets of ice tend to bounce upon contact and may accumulate enough to cover the ground - even to a depth of several inches.
• Snow Squall: An intense fall of accumulating snow reducing visibility significantly and often accompanies by increased winds.
• Heavy Snow: Six inches or more of snow in 24 hours for widespread (synoptic) snow and six inches in 24 hours for lake effect snow.

Watches
Just as with summer weather, the National Weather Service attempts to issue a Watch to alert the public of the potential for severe winter weather.

• Winter Storm Watch: Conditions exist for the possible occurrence of severe winter weather such as blizzard conditions, heavy snow, significant freezing rain, or heavy sleet. Usually issued 12 to 36 hours in advance of the winter storm.

Warnings
A Warning is issued to alert the public of imminent severe winter weather. Normally, a warning is issued after a winter storm watch has been in effect. If a winter storm develops quickly, then the warning may not have been preceded by a watch.

• Winter Storm Warning: Issued when heavy snow, significant freezing rain, or heavy sleet is expected to occur. Usually issued 6 to 18 hours in advance of the winter storm.
• Blizzard Warning: Issued when sustained or gusty winds of 35 MPH or better is expected to reduce visibility at or below a quarter of a mile due to falling and/or blowing snow for at least three hours.
• Winter Storm Warning for Lake Effect Snow: Issued when heavy, primarily lake effect snow is expected. Lake effect snow is most common over extreme Northeast Ohio.
• Wind Chill Warning: Issued for wind chills below -25 degrees Fahrenheit.

Advisories
A less severe winter weather event will prompt the issuance of an Advisory. An Advisory is named specific to the weather event expected and issued when the event is expected to be widespread. Travel by foot or vehicle may be dangerous during an advisory even if the winter weather is not expected to reach winter storm criteria. Some examples of Advisories are:

• Winter Weather Advisory for Snow: A fall of snow within 12 hours of usually three to five inches.
• Winter Weather Advisory for Lake Effect Snow: A snowfall of three to five inches of primarily lake effect snow over the snowbelt of Northeast Ohio.
• Winter Weather Advisory for Freezing Rain: A glaze of ice expected from freezing rain that may hamper travel.
• Winter Weather Advisory for Blowing and Drifting Snow: Blowing and drifting snow will occasionally reduce visibility to and eighth of a mile or less with significant drifting in open areas.
• Wind Chill Advisory: Wind chill temperatures are expected to be 10 to 25 degrees below zero for an extended period of time.
• Dense Fog Advisory: Dense for that reduces visibility to less than one-quarter mile.
• Winter Weather Advisory: Issued when two or more of the above conditions are expected.

Thanks to Gary Garnet, Warning and Coordination Meteorologist for the National Weather Service office in Cleveland.