What Is Thundersnow?

Jessica Kourkounis, Getty Images
Jessica Kourkounis, Getty Images

The northeastern United States is dealing with its second major nor'easter in a week, with rain and heavy snow—and the associated power outages—cutting a path across the Mid-Atlantic and New England. But news of the adverse impacts of the snowstorm is being accompanied by an unusual buzzword: thundersnow. Thundersnow occurs during a thunderstorm that produces snow instead of rain. The mechanisms that produce rainy thunderstorms and snowy thunderstorms are largely the same, even if the air temperature is below freezing.

A band of snow can become strong enough to produce lightning through two processes known as convection and forcing. Convection occurs when an area of warm air quickly rises through cooler air above it. Convective snow is most common during lake effect snow events like those you’d find on Lake Ontario or Lake Erie, since the process requires extreme vertical temperature gradients that can result from bitterly cold air flowing over a warm body of water.

Forcing is slightly different. A strengthening low-pressure system involves fast, dynamic changes in the atmosphere, especially when one of these storm systems quickly gains strength. Such a fast-developing storm can cause large amounts of lift in the atmosphere, a process that forces air to swiftly rise like you’d see during convection. This creates intense bands of snow that can grow so strong that they produce thunder and lightning. This process is responsible for the thundersnow that occurs during blizzards and nor’easters, those powerful storms that regularly hit the eastern coast of the U.S. during the winter. Thundersnow can be pretty exciting—just ask The Weather Channel's Jim Cantore:

The name “thundersnow” can be a bit misleading. One of the most enjoyable things about a snowfall is how silent it is outside when there’s a thick blanket of snow on the ground. Snow absorbs sound waves so efficiently that you can usually only hear ambient noises immediately around where you’re standing. Snow muffles the sound of thunder for the same reason. Thunder that might be audible for many miles during a rainy thunderstorm might only be audible for a few thousand feet away from where the lightning struck. Unless the lightning strikes very close to where you are, you might only see a bright flash during thundersnow without ever hearing the thunder.

While thundersnow is a fascinating phenomenon to encounter, it does involve lightning, after all, and it’s just as dangerous as any other lightning bolt you’d see in a rainy thunderstorm. If you’re ever lucky enough to experience thundersnow, the event is best enjoyed indoors and out of harm’s way.

This piece originally ran in 2017.

Lake Michigan Has Frozen Over, and It's an Incredible Sight

Scott Olson, Getty Images
Scott Olson, Getty Images

A polar vortex has brought deadly temperatures to the Midwest this week, and the weather is having a dramatic effect on one of the region's most famous features. As the Detroit Free Press reports, parts of Lake Michigan have frozen over, and the ice coverage continues to grow.

The Lake Michigan ice extent has increased rapidly throughout January, starting around 1 percent on the first of the month and expanding to close to 40 percent by the end of the month. Yesterday was the coldest January 30 in Chicago history, with temperatures at O'Hare Airport dropping to -23°F. Even though it's frozen, steam can be seen rising off Lake Michigan—something that happens when the air above the lake is significantly colder than the surface. You can watch a stream of this happening from a live cam below.

Lake Michigan's ice coverage is impressive, as these pictures show, but it's still far from breaking a record. Though Lake Michigan has never frozen over completely, it came close during the winter of 1993 to 1994 when ice reached 95 percent coverage.

Midwestern states like Wisconsin, Michigan, Illinois, and Indiana aren't the only places that have been hit hard by the cold this winter. At the United States/Canada border, Niagara Falls froze to a stop in some spots, a phenomenon that also produced some stunning photographs.


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[h/t Detroit Free Press]

Why You Need to Keep Your Car's Gas Tank Full in Cold Weather

iStock.com/Chalabala
iStock.com/Chalabala

Schools, trains, and the U.S. Postal Service have shut down this week as a polar vortex brings negative double-digit temperatures to the Midwest. Even if residents won't be doing much traveling as long as the dangerous weather persists, they'd benefit from keeping a full tank of gas in their cars: According to the Detroit Free Press, it's an easy way to prevent fuel lines from freezing.

One common reason cars struggle to start in cold weather is blocked-up fuel lines. These tubes are thin, and if there's any moisture in them when temperatures drop to extreme levels, they can freeze, causing blockages that prevent fuel from flowing.

Gasoline, on the other hand, doesn't freeze as easily. It maintains its liquid state in subzero temperatures, like those currently hitting parts of the U.S., so when a gas tank is full, those fuel lines are better equipped to handle to the cold.

If you filled up your tank before the recent cold snap and your car still won't start, it may have something to do with your antifreeze levels. Your car's radiator needs water to work properly, and antifreeze is what keeps the water liquid when temperatures dip below 32°F.

Of course, if temperatures have already dropped to dangerous levels in your area, it's not worth it to drive to the gas station to refuel or run out to stock up on antifreeze. Instead, keep these car maintenance tips in mind for the next time an arctic blast rolls in to town. And when it is safe enough to drive again, resist heating up your engine in the driveway: Letting your car idle in the cold can actually shorten the engine's lifespan.

[h/t Detroit Free Press]

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