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What’s the difference between a snow squall and a blizzard? Weather advisories demystified

Jodi Westrick
Michigan Radio
Snowy Ann Arbor weather in February 2019.

Michigan has received a dizzying number of different weather-related warnings over the past two months, ranging from severe cold to freezing rain--and now, snow squalls. Most of these warnings are related to travel conditions. But what do they really mean?

Snow squalls

Snow Squall
Credit National Weather Service

The national weather service issued a warning for snow squalls on Monday, March 4. Snow squalls are fast-moving bursts of heavy snow. They result in white-out conditions, while falling temperatures can freeze road surfaces within minutes. The combination makes road conditions potentially very hazardous.

Snow squalls have localized effects and last for very brief periods of time--only about 30 to 60 minutes. In contrast, a snow storm lasts hours or even days. Although snow accumulations from a snow squall are typically an inch or less, they cause a disproportionate number of deadly traffic accidents. 

The national weather service recommends avoiding all travel during a snow squall. If you are on the highway and can’t exit, you should reduce your speed and turn on your headlights, maintaining a safe distance from the car in front of you. Slamming on the brakes can cause you to lose control of your vehicle.

Credit National Weather Service

Snow storms

Michiganders have hunkered down through snow storms on almost a weekly basis this winter. According to the National Weather Service, Detroit has received more than 20 inches of snow this season, and Grand Rapids residents have been pummeled with over 50 inches.

Blizzards are snow storms with winds or gusts of 35 mph or more, resulting in reduced visibility on the roads. Blowing snow is wind-driven snow that could be falling or picked up from the ground.

Ordinary falling snow is referred to as a snow shower, and flurries are lightly falling snow.

Lake effect snow

In addition to snowy winter weather typical of the upper midwest, Michigan receives extra snow in the form of lake effect snow. This type of snow happens when cold air moves across the Great Lakes. For Michigan, a lot of lake effect snow is formed over Lake Michigan. Warmth and moisture from the lake are carried up into the atmosphere, creating snow that falls in areas near the lake. West Michigan and parts of the Upper Peninsula experience heavy lake effect snow most winters.

Ice storms

Downed tree
Credit Dustin Dwyer / Michigan Radio
Michigan Radio
February 2019 ice storms caused power outages and hazardous conditions in Grand Rapids.

Icy weather can be extremely dangerous. Ice accumulation from freezing rain can cause tree limbs and utility poles to fall, disrupting power. These power outages can last days at a time. In early February 2019, over one hundred thousand homes across the state lost power, and it was several days before power was completely restored.

Ice on the roads is hazardous and motorists are advised to use caution or avoid driving  altogether when they are covered with ice. Black ice is a type of ice that is not always obvious. It’s called black ice because it’s transparent, and the black color of the pavement shows through. Black ice is notorious for causing accidents because drivers are not aware the road is ice-covered.

Ice can also cause dangerous slip and fall accidents on sidewalks.

Windchill and extreme cold

Extremely cold air can freeze skin quickly, leading to frostbite. Prolonged exposure to cold can also cause hypothermia. The risk of exposure to cold air increases as the temperature drops. Under extremely cold conditions or a wind chill advisory, it is recommended that people avoid being outside, and, when it is necessary to go outside, to dress warmly, covering exposed skin. Make sure your gas tank is full when you travel, and keep an emergency kit in your car containing things like jumper cables, food, water, blankets, and hand warmers.

Credit National Weather Service

Types of warnings

A winter weather advisory means that potentially dangerous winter weather is expected within the next 12 to 36 hours or is already occurring. Motorists should be aware that the weather could cause travel difficulties. A winter storm warning means that dangerous winter weather is already occurring or is predicted to begin within 36 hours, and will cause significant problems for travelers. People should respond to a winter storm warning by taking action to stay safe--that may mean changing or canceling plans. A blizzard warning means that severe winter weather is expected within 36 hours that will include whiteout conditions. No one should travel during a blizzard warning.

Catherine Shaffer joined Michigan Radio in 2014. She works in the newsroom and specializes in stories related to the life sciences, health, and technology. Catherine earned a bachelor’s degree in Biochemistry from Michigan State University and a Master’s from University of Michigan. Prior to Michigan Radio, Catherine has worked as a freelance writer, mainly in focusing on biotechnology and the pharmaceutical industry, since 2001. She is also an award-winning fiction writer. When not at work, Catherine enjoys being in the outdoors and practicing yoga.
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