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.

Wayfair’s Fourth of July Clearance Sale Takes Up to 60 Percent Off Grills and Outdoor Furniture

Wayfair/Weber
Wayfair/Weber

This Fourth of July, Wayfair is making sure you can turn your backyard into an oasis while keeping your bank account intact with a clearance sale that features savings of up to 60 percent on essentials like chairs, hammocks, games, and grills. Take a look at some of the highlights below.

Outdoor Furniture

Brisbane bench from Wayfair
Brisbane/Wayfair

- Jericho 9-Foot Market Umbrella $92 (Save 15 percent)
- Woodstock Patio Chairs (Set of Two) $310 (Save 54 percent)
- Brisbane Wooden Storage Bench $243 (Save 62 percent)
- Kordell Nine-Piece Rattan Sectional Seating Group with Cushions $1800 (Save 27 percent)
- Nelsonville 12-Piece Multiple Chairs Seating Group $1860 (Save 56 percent)
- Collingswood Three-Piece Seating Group with Cushions $410 (Save 33 percent)

Grills and Accessories

Dyna-Glo electric smoker.
Dyna-Glo/Wayfair

- Spirit® II E-310 Gas Grill $479 (Save 17 percent)
- Portable Three-Burner Propane Gas Grill $104 (Save 20 percent)
- Digital Bluetooth Electric Smoker $224 (Save 25 percent)
- Cuisinart Grilling Tool Set $38 (Save 5 percent)

Outdoor games

American flag cornhole game.
GoSports

- American Flag Cornhole Board $57 (Save 19 percent)
- Giant Four in a Row Game $30 (Save 6 percent)
- Giant Jenga Game $119 (Save 30 percent)

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Expeditions Gather Climate Change Clues on Mount Everest in Two New Documentaries

Team members climb up a slope during the expedition to find Sandy Irvine's remains on Mount Everest.
Team members climb up a slope during the expedition to find Sandy Irvine's remains on Mount Everest.
Matt Irving/National Geographic

Two one-hour documentaries premiering tonight reveal what Mount Everest is really like—and what scientists can learn from studying it.

Both docs are produced by and airing on National Geographic. In Lost on Everest, premiering at 9 p.m. EDT, climber Mark Synnott and Nat Geo photographer Renan Ozturk lead a team of seasoned mountaineers on a mission to discover what happened to Andrew “Sandy” Irvine, who vanished with fellow explorer George Mallory during the first Everest climb in June 1924. While Mallory’s body was located by a BBC-sponsored operation in 1999, Irvine’s exact fate has remained a mystery for nearly a century since his disappearance. As Synnott and his companions search for evidence, they encounter their own harrowing set of obstacles, from hurricane-force winds to medical emergencies.

Climbers on Mount Everest
Climbers ascend the Khumbu Icefall, a notoriously dangerous section of the summit route.
Mark Fisher/National Geographic Society

But Mount Everest isn’t only a challenge for adventure-seekers and intrepid investigators—it also holds thousands of years’ worth of information about how climate change has altered the environment, which can help scientists predict its future effects. In Expedition Everest, airing at 10 p.m. EDT, actor Tate Donovan narrates the journey of an international group of scientists and climbers with an ambitious set of data-collecting objectives.

One task is to use drones, laser scanners, and cameras to capture footage of every inch of the ascent, so researchers can create a 360-degree portrait of the mountain and track how glacial melt alters the landscape in the coming years. Since the Himalayas contain the water supply for roughly one-fourth of the world’s population, the increase in glacial melt—which has already doubled since 2000—could threaten the futures of billions of people living in the region.

Scientists drill ice cores on Mount Everest
Mariusz Potocki and members of the National Geographic and Rolex Perpetual Planet Everest Expedition team collect the highest-ever ice core at 8020 meters (26,312 feet) near the South Col of Everest.
Dirk Collins/National Geographic Society

Even more immediate is the risk of flash floods, which are difficult to predict without a constant feed of weather data from high altitudes. Another goal of the expedition is to install weather stations at five locations along the climbing route, which will monitor temperature, humidity, air pressure, wind speed, and other factors that help alert meteorologists to an impending flood.

Some researchers have joined the expedition to drill deep into the ice at an altitude above 8000 meters (26,000 feet)—Mount Everest's "death zone"—and collect ice cores. These long tubes of ice reveal how the atmosphere has changed over thousands of years. Others are collecting similar cores of sediment at the bottom of a lake, as well as examining how plant and animal life has adapted to the warming temperatures and rising water levels.

Overall, Expedition Everest illustrates how the Himalayas function as an early indicator of what climate change will do to other places.

As climate scientist Anton Seimon explains in the documentary, “We’re getting a window into what the rest of the world is starting to experience—and likely to experience in growing proportions.”

You can watch the double feature tonight, June 30, at 9 p.m. EDT on National Geographic.