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Thundersnow Storms: Extraordinary Winter Weather

Beth writes on a wide variety of subjects. She loves to wonder about the world, and the science of why things happen.

What is thundersnow?

What is thundersnow?

Thunder With a Snowstorm Is Rare

It’s very strange when thundersnow happens. It’s a combination of a normal thunder and lightning storm, but with snow falling instead of rain. You hear a crack of thunder, or see a flash of lighting, but all around you a heavy blizzard of snow is falling. Normally, winter whiteouts are accompanied by absolute silence as the snowfall muffles all sound, but a thundersnow storm is an alarming alternative.

It used to be thought this was a rare phenomenon, but in recent years, more thundersnow events are being observed. Between six and ten of these storms are observed every year in the US. Many more go unrecorded as they occur in sparsely populated areas, and so are not catalogued by news media. The video below shows just how excited experts get when this weather event occurs.

Jim Cantore Awestruck By Rare Thundersnow

What Causes Thundersnow?

A normal thunderstorm happens when there is an elevated convection of air. Convection is the movement of warm air rising through the atmosphere. The warm air carries moisture from the lower levels of the atmosphere through to the upper levels where they form rain clouds. Elevated convection is where moist warm air rises to a greater height than normal (to the troposphere) and the high density of moisture present forms thunder rainclouds.

For a thunder and lightning snowstorm (thundersnow) to occur, not only must conditions be right for elevated convection to happen, but in addition a cold air stream must have become trapped above the warm air stream. This means that the moisture trapped in the thunder clouds is reduced in temperature, and therefore falls as snow rather than as rain.

When the storm breaks, a heavy snowfall occurs in tandem with the thunder and lightning associated with a normal thunderstorm. This gives rise to freakish booms and crackles not normally heard when snow falls. The meteorologist Al Roker gives a clear explanation of the phenomenon in his book about extreme weather.

How a Blizzard Creates Thundersnow

US Mid-West and UK Thundersnow Storms

Thundersnow is most likely to occur in late winter or early spring. For example, a thundersnow storm struck Chicago in 2011 when 3 inches of snow fell per hour over a ten-hour period, accompanied by rumbling thunder and lightning flashes.

In February 2013 two memorable periods of thundersnow events were widely reported. Although several days apart, their effects were similar. They caused widespread disruption and triggered fear and panic in local populations.

The first of these snowstorms was in the UK and occurred across the cities of Manchester, Sheffield, Glasgow and Edinburgh on February 5th 2013. A few days later, this was followed by a number of thundersnow storms across the American Midwest. These started around February 10th and continued sporadically until the end that month.

The snowstorms trekked across the central United States. The Central Plains area experienced snowfall rates as high as four inches per hour, along with thunder and lightning. The video below captures the sound and vision of a thundersnow event that happened in Kansas on 21st February 2013.

Heavy snow blizzards with thundersnow were also experienced across the US during February 2014. Up to eight inches of snow fell on Chicago, Illinois on February 17th 2014 in just a few hours.

CNN Cameras in Kansas Capture Thundersnow

Why is Thundersnow Dangerous?

The main problem is the element of surprise. People don't expect to hear thunder in the middle of a snowstorm. It can cause them to panic, and be fearful.

On a practical level, the intensity of the blizzard causes poor visibility and is a danger to traffic. There is a greater chance of car accidents and vehicle pile-ups in heavy snow. The best advice is if you hear a thundersnow storm is likely in your area, don't take your car out, don't drive, keep indoors, and stay warm and dry.

The US National Weather Service estimates that thunder and lightning snowstorms account for less than 1% of all snowstorms. However, their effect on normal life is dramatic, because the storm is very slow moving; almost stationary until it has dropped its cargo of snow. This results in a heavy blizzard of snow being dropped in a very short time over a static area.

The Dangers of Thundersnow Storms

An interview with WGN Meteorologist Tom Skilling in Red Eye Chicago on February 17th 2014 revealed the following dangers associated with thundersnow events.

  1. The lightning produced during a thundersnow storm is more likely to be positively charged (compared to that produced during a “normal” thunder-storm.) This means that damage to property or injury to people is more likely to result if a lightning strike occurs.
  2. Lightning produced during a thundersnow event typically lasts longer and is more powerful than that generated during a normal thunderstorm.
  3. Lightning and thundersnow is more common than records suggest. Often the flashes of lightning can be masked by heavy snowfalls and so go unnoticed by people.
  4. The heavy snowfall during a thundersnow event can deposit between 4 and 8 inches of snow an hour, and produce whiteout conditions which make driving conditions hazardous.
A thundersnow storm results in heavy snowfall over a small area.

A thundersnow storm results in heavy snowfall over a small area.

What Does Thundersnow Look Like? And Where Can You See It?

If you see aa thundersnow storm at night, the lightning flashes appear brighter than normal. This is because the light is reflected off the falling snowflakes. Conversely, the thunder within a thundersnow event sounds quieter as the falling snow absorbs and dampens the sound. Thunder from a typical thunderstorm can be heard many miles away, the thunder during thundersnow will only be heard if you are within 2 to 3 miles of the storm.

Thundersnow is a naturally occurring, but seemingly random event. Scientists monitor and record as many of them as possible. They hope to learn how, when and where these extraordinary snowstorms occur, and so be able to better predict the next one.

These events appear to be happening more frequently, but so far, no one knows why. If you want to try and catch this strange storm for yourself, two places that regularly experience thundersnow events are Wolf Creek Pass, Colorado, and the eastern shores of Lake Ontario.

Four Types of Thundersnow

There are four types of thundersnow.

  1. A common thunderstorm on the leading edge of front that runs into a front of the opposite temperature and where the precipitation takes the form of snow.
  2. A heavy, large-scale snowstorm that sustains strong upward mixing with cyclonic winds which allows for favorable conditions for lightning and thunder to occur.
  3. A lake effect or ocean effect thunderstorm which is produced by cold air passing over relatively warm water; this commonly produces snow squalls over the Great Lakes.
  4. A cold front containing extremely cold air up high and strong upward air movement from down low which allows for favorable conditions for lightning and thunder to occur.

Information from “A Climatology of Thundersnow Events over the Contiguous United States.” by Market, Patrick S., Chris E. Halcomb, Rebecca L. Ebert, 2002

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

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