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A Record Heatwave in the Southwest Grounds Planes

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The first week of summer is getting off to an especially hot start in the American Southwest. According to ABC News, temperatures reached 118°F on Monday, June 19, tying the regional record for that day set last year. Today, Tuesday, June 20, the mercury is expected to climb even higher, and airlines in Phoenix are canceling flights as a precaution.

American Airlines grounded close to 50 flights scheduled to take off from Sky Harbor International Airport in Phoenix Tuesday morning, The Arizona Republic reports. With the National Weather Service predicting highs of 119°F, the Bombardier CRJ aircraft used by the airline for regional flights has been deemed unfit to travel.

The maximum operating temperature of the Bombardier CRJ aircraft is 118°F—at that point, experts worry that the air is no longer dense enough for the plane to take off and fly efficiently. Extreme heat isn’t a common problem for airlines, with temperatures approaching the 120s in the Southwest less than one day a year on average. But this summer is already shaping up to be one for the record books. Above-average heat is projected to scorch the region from now through September. The forecast fits into a recent trend of intense Southwestern summers which scientists believe are connected to climate change.

While many local flyers will be inconvenienced by the heat today, travelers flying beyond Arizona can expect a smooth trip. Larger jets, like Boeing and Airbus, have maximum operating temperatures of 126°F and 127°F, respectively—higher than any temperature that's been recorded in Phoenix to date.

[h/t ABC News]

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Weather Watch
Thanks to Desert Dust, Eastern Europe Is Covered in Orange Snow
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Certain areas of Eastern Europe are starting to look a bit like Mars. Over the last few days, snowy places like Sochi, Russia have experienced an unusual snowfall that coated mountains in orange powder, according to the BBC.

The orange snow was the result of winds blowing sand from the Sahara east to places like Moldova, Romania, Bulgaria, Ukraine, and Russia. The sand mixes with precipitation to form orange-tinted snow. According to the BBC, the phenomenon occurs semi-regularly, turning snow orange about once every five years, but this year is especially sandy. As a result, skiers are navigating slopes that look like they're from a different world, as you can see in the video below from The Guardian.

The Sahara rarely gets snow, but when it does, the landscape can look somewhat similar, as you can see in this image of the Atlas mountains in Morocco.

Instagram is currently filled with photos and videos from Eastern Europe featuring the odd-looking snow. Check out a few samples below.

[h/t BBC]

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Weather Watch
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.

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