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Scott Olson/Getty Images
Scott Olson/Getty Images

Storms Head Across the U.S. This Week

Scott Olson/Getty Images
Scott Olson/Getty Images

We just lived through one of the warmest winters in recent memory. The warmth and relative lack of storminess was odd compared to a normal year, but the weather was downright quiet compared to what we've seen over the last couple of years. Unfortunately, our luck is running out as the Sun creeps into the Northern Hemisphere and the atmosphere slowly warms up. The clash of the seasons will cause a steady train of storms to glide across the country through the end of March, bringing along with them noticeably rapid changes in weather from day to day, including the risk for severe thunderstorms and some beneficial heavy rainfall.

The forecast position of the jet stream from the GFS weather model on the evening of Monday, March 27, 2017, showing three troughs (southward dips) in the jet stream as they cross the United States. Image Credit: Tropical Tidbits

 
Current weather models suggest that a series of upper-level troughs—elongated areas of lower air pressure—will come ashore on the West Coast every couple of days for the next two weeks, each wave taking about three days to traverse the length of the United States before retreating over the Atlantic Ocean. Each trough will be sandwiched between ridges of high pressure, which are associated with warmer air and calmer skies. This trough-ridge combination will allow warm, unstable air to flow north from the Gulf of Mexico before the trough arrives to take advantage of the favorable atmosphere ahead of it. The end result will be heavy rain and thunderstorms, some of which could turn severe.

The greatest risk for severe thunderstorms with each wave will lie across the southern Plains and interior sections of the Gulf Coast states, exactly where you'd expect dangerous weather to develop at the end of March. The extent of the severe weather depends on how much instability, moisture, and wind shear are present when the storms bubble up. If the right mix of ingredients doesn't come together at the right time, the weather won't be much more than an inconvenience. If storms are able to take advantage of the right conditions, though, all types of severe weather—damaging winds, large hail, and tornadoes—will be possible with each outbreak of severe thunderstorms.

It shouldn't come as too much of a surprise that severe weather is ramping up as we get closer to April. We're rapidly approaching prime season for severe thunderstorms and tornadoes. The average number of tornadoes that touch down each day climbs rapidly between the end of March and the beginning of summer, with each day of spring becoming historically more favorable for nasty severe weather outbreaks.

The Weather Prediction Center's precipitation forecast (in inches) between March 24 and March 31, 2017. Image Credit: NOAA/WPC

 
The silver lining to the cycles between calm and stormy is that it will bring much-needed rain to just about everyone east of the Rockies who are currently experiencing drought conditions. The same weather pattern that allowed California to climb out of its drought in just a couple of months also dried the eastern half of the country to the point of drought. Moderate to severe drought conditions covered nearly 16 percent of the contiguous United States on the U.S. Drought Monitor's analysis for March 21, with the worst drought covering the central Plains and much of the East Coast.

Rain from the upcoming train of storm systems will drop several inches of rain over a widespread area, helping to put a small dent in the drought. It won't be enough to cure the parched earth in many places, but as Californians will tell you, any amount of rain can help.

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Weather Watch
Thanks to Desert Dust, Eastern Europe Is Covered in Orange Snow
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iStock

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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