Safety - Winter Definitions

It is important that you learn and understand the definitions of different winter related headlines. Here are the main products used by the NWS to keep people informed.

Hazardous Weather Outlook (HWO)

The Hazardous Weather Outlook includes any potential weather hazard out to seven (7) days. It is used for planning purposes and will include a short description of what the weather threat is, when it is expected, and how much it may impact the region. The HWO is issued daily around 5:00 AM, and updated during the day as needed.

Winter Storm Watch, Lake Effect Snow Watch (WSW)

Watches are issued when there is a potential for a winter storm to affect the region that will produce at least warning level snow (8 inches of snow in 12 hours or 10 inches of snow in 24 hours), strong winds, low wind chills, or mixed precipitation during the next 1 to 3 days. It does not always mean the area will be hit by a winter storm, but there is still some uncertainty of the exact path or timing of the event. This is a planning stage. Use this time to ensure you have supplies at home, like some extra food, medications, baby items, etc.. If travel is planned, check ahead and see if a different route or delaying your departure may make your trip safer. Be alert for changing weather conditions.

Winter Weather Advisory, Lake Effect Snow Advisory (WSW)

Advisories are issued for those winter weather events that are expected to be more of an inconvenience and should not become life-threatening if caution is exercised. These are often issued for 3 to 8 inches of snow, blowing and drifting snow, freezing drizzle, or a combination of these elements. 

Winter Storm Warning,  Lake Effect Snow Warning (WSW)

Warnings are usually issued when dangerous winter weather is expected, occurring, or imminent. The weather can become life-threatening. Criteria includes snowfalls of 8 inches or more in 12 hours or 10 inches in 24 hours, or lower amounts if accompanied by strong winds or a combination of dangerous winter elements. Avoid unnecessary travel.

Blizzard Warnings (BZW)

The most dangerous winter event is certainly the blizzard. Blizzard Warnings are issued when snow or blowing snow lowers visibilities to a 1/4 mile or less, wind gusts hit 35 mph or higher, and the storm lasts for 3 hours or more. Travel is dangerous and should be avoided if possible.

Ice Storm Warning (WSW)

Ice storm Warnings are issued when freezing rain will cause widespread glazing. A coating of ice is expected to reach 1/4 inch thick or more on objects and make travel nearly impossible. For lesser amounts of ice, usually a winter weather advisory would be used, but even a thin glaze of ice can make travel difficult. Avoid travel.

Wind Chill Warning (WSW)

Issued when the apparent temperature reaches -35 F or lower in eastern Upper Michigan, and -30 F or lower in northern Lower Michigan.  A wind chill advisory is issued for values between -25 and -35 F  across eastern Upper Michigan and -20 to - 30 F for northern Lower Michigan. . Dress warmly and cover as much exposed skin as possible.