A winter weather advisory was in effect for some Metro Detroit counties on Friday as more snow falls across the region.
Snow was expected to fall throughout the morning and some of the afternoon on Friday, Jan. 19, causing slippery road conditions and affecting the morning commute. Southeast Michigan was forecast to pick up an extra 1-3 inches of snow on Friday, with those more southeast and northeast receiving the most snow. See the full forecast here.
Winter weather advisories were in effect for the following counties at the following times:
- Until 1 p.m. Friday for Washtenaw, Wayne, Lenawee and Monroe counties.
- Until 4 p.m. Friday for the Thumb region, including Sanilac and St. Clair counties.
What exactly is a winter weather advisory?
There are different types of notices issued by the National Weather Service due to inclement or dangerous weather. These advisories are meant to help warn people of any danger and let them know what conditions to expect.
Here are some important winter weather terms to know.
What is a winter storm?
A winter storm occurs when there is heavy snow in combination with blowing snow, cold temperatures, wind, rain, freezing rain and/or sleet. It is still a dangerous storm and can be life threatening.
During a winter storm, the NWS says at least 8 inches of snow or more falls within 12 or more hours, or at least 6 inches or more falls between 6-9 hours.
Winter storm watch
A winter storm watch is an advisory that is issued due to potentially severe winter weather that could occur within 48 hours. The key word in this type of advisory is “watch,” as hazardous or severe weather is not necessarily imminent, but it is possible.
The NWS defines significant and hazardous weather as a combination of:
- 5 inches or more of snow and/or sleet within a 12-hour period, or 7 inches or more of snow and/or sleet within a 24-hour period; and/or
- Enough ice accumulation to cause damage to trees or power lines; and/or
- A life threatening or damaging combination of snow and/or ice accumulation with wind.
Winter storm warning
A winter storm warning is issued when a “significant combination of hazardous winter weather is occurring or imminent,” the NWS says.
Again, such weather is defined as a combination of:
- 5 inches or more of snow and/or sleet within a 12-hour period, or 7 inches or more of snow and/or sleet within a 24-hour period; and/or
- Enough ice accumulation to cause damage to trees or power lines; and/or
- A life threatening or damaging combination of snow and/or ice accumulation with wind.
Click here for tips from the Red Cross on staying safe during severe winter weather.
Winter weather advisory
A winter weather advisory is issued when winter weather is approaching and expected to cause a “significant inconvenience,” but is not severe enough to require a warning to be issued.
During a winter weather advisory, expected precipitation includes any amount of freezing rain, or 2-4 inches of snowfall -- which could be on its own or in combination with sleet and freezing rain.
Wind chill warning
A wind chill warning is issued when “dangerously cold wind chill values are expected or occurring,” the NWS says.
Those in an area under a wind chill warning are urged to stay indoors during the coldest parts of the day. If going outside is necessary, people are urged to cover all exposed skin and dress in layers.
The NWS also encourages notifying someone where you’re going and when you get there.
Wind chill watch
A wind chill watch is similar to a wind chill warning. The only difference: A watch is issue when dangerously cold wind chill values are possible, but not necessarily expected or occurring.
If a watch is issued, people are urged to take steps necessary to be prepared, such as adjusting plans, preparing a winter survival kit for your car, and ensuring your vehicle has a full tank of gas.
Wind chill advisory
A wind chill advisory is issued when current or expected wind chill values are seasonably cold, “but not extremely cold,” according to the NWS. Under these conditions, people are urged to dress warm and cover exposed skin when going outside.
This advisory is less severe than a wind chill warning or watch.
High wind warning
A high wind advisory is issued when an area is expected to experience sustained winds of 40 mph or greater, with gusts of 58 mph or greater.
These strong winds can pose dangers to people and infrastructure. The NWS says high winds can “cause downed trees and power lines, flying debris and building collapses, which may lead to power outages, transportation disruptions, damage to buildings and vehicles, and injury or death.”
When a high wind warning has been issued, the National Weather Service says people should seek shelter. Anyone driving is urged to slow down and keep both hands on the wheel.
High wind watch
A high wind watch is similar to a high wind warning, particularly when it comes to the criteria.
The only difference is that a high wind watch is issued when the following conditions are possible, but not exactly expected or imminent:
- Winds with sustained speeds of 40 mph or higher for one hour or more, or
- Wind gusts at 58 mph or higher for any duration.
In comparison, a high wind warning is issued when those conditions are actually expected or imminent.
What is a blizzard?
A blizzard is a severe snowstorm in which there are strong winds and little-to-no visibility. This type of storm is more hazardous than a regular winter storm, and typically lasts for at least a few hours.
When is a blizzard warning issued?
According to the NWS, a blizzard warning will be issued if the following conditions are “occurring or expected” within the next 12-18 hours:
- Snow and/or blowing snow reducing visibility to a quarter mile or less for 3 hours or longer, and
- Sustained winds of 35 mph or greater, or frequent gusts to 35 mph or greater.
Officials say there is “no temperature requirement that must be met to achieve blizzard conditions.”
During a blizzard, people are urged to stay indoors and avoid driving or being outside in order to stay safe.
What is an ice storm?
The NWS says an ice storm is when a “significant, and possibly damaging,” accumulation of ice occurs. This normally looks like a coating of at least a quarter of an inch, but could be up to a half an inch if winds are slower than 15 mph, officials say.