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By Alan Smith, Meteorologist Posted 13 days ago June 4, 2024

Tornadoes in the Mountains: A Historical Overview

Tornadoes don't happen in the mountains, right?

Wrong!

While it is true that tornadoes are less common in mountainous terrain compared to the plains, under the right conditions, they can and do occur in the mountains. In fact, numerous strong to violent tornadoes have occurred in both the Appalachian and Rocky Mountains and weak tornadoes have been documented as high as 12,156 feet in the Sierra Nevada Mountains.

One thing that tornadoes and mountain weather have in common is that they are both influenced by micro-scale meteorological factors. When you combine these two characteristics, you can end up with some fascinating (and also destructive) events in atypical locations.

What is a Tornado?

A tornado is a violently rotating column of air extending vertically from the ground to the base of a thunderstorm. Tornadoes often have a visible funnel with a rotating cloud of debris from the ground, but in some instances may be completely obscured by rain. 

Tornado Intensities and Ratings

Tornadoes come in many shapes and sizes and can range from short-lived weak events to long-lived, violent events that destroy buildings, homes, and forests. Tornadoes can range from 100 feet or less in width to more than a mile wide. 

Tornadoes were originally rated on the Fujita (F) scale (F-scale) on a rating system from 0 to 5, with 5 being the strongest. However, in 2007, the U.S. National Service began rating tornadoes using the Enhanced Fujita (EF) scale, which takes into account more thorough damage surveys and wind estimates. This newer scale still rates tornadoes from 0 to 5.

Tornadoes rated EF-2 or EF-3 are classified as strong tornadoes and can cause significant damage. Tornadoes rated as EF-4 or EF-5 are the most rare and are classified as violent tornadoes that cause catastrophic damage.

The Fujita and Enhanced Fujita scales are named after Dr. Ted Fujita, a pioneering scientist and tornado researcher who studied twisters and the damage they produced extensively from the 1950s until his death in 1998. Dr. Fujita was often referred to as "Mr. Tornado".

Tornado Ingredients

  • Moisture and Instability – At a minimum, the same ingredients for thunderstorms are also required for tornadoes, but typically at a much larger magnitude than is required for an ordinary thunderstorm. Warm, moist air is necessary for severe thunderstorms to develop, and when moisture levels are higher than usual, this can fuel an extremely unstable atmosphere.

  • Wind Shear – Changes in wind speed and direction with height can help a thunderstorm tilt and rotate. Increasing wind speeds with altitude help to "tilt" the updraft of a thunderstorm, helping the storm to sustain itself for longer by cutting off the updraft (warm rising air) from the downdraft (rain-cooled air).

    Winds that change direction in a clockwise manner with height can help a storm rotate. For example, winds blowing out of the southeast at the surface, southwest in the mid levels of the atmosphere, and west in the upper levels of the atmosphere can help a storm rotate.

    Strong directional wind shear in the low levels of the atmosphere in particular are more likely to support the development of a tornado.

Why are Tornadoes Less Common in the Mountains than on the Plains?

Tornadoes are most common in the Central U.S. in between the Rockies and the Appalachians. This region has an open door to intrusions of warm, moist air from the Gulf of Mexico, which frequently coincides with cooler and drier air from the northwest. The interaction of these airmasses can lead to high levels of instability and wind shear that can support severe thunderstorms and tornadoes.

One reason why tornadoes are less common in the mountains is the fact that temperature decreases with altitude, and by comparison, higher-elevation terrain is typically cooler and more stable than lower-elevation terrain.

Also, significant terrain barriers such as the Rockies and the Appalachians can disrupt wind flow patterns and act as barriers to rich moisture (the latter of which is especially true in the Rockies). 

However, the ingredients occasionally line up to support tornadic development in mountainous terrain, and when this does occur, some studies have shown that mountainous terrain can actually enhance tornadic development.

How Mountainous Terrain Can Enhance Tornadic Development

Studies have suggested that localized wind flow patterns that occur in complex terrain can actually enhance tornadic development when other pre-existing ingredients are in place (Schneider, 2009).

Also, rapid increases and decreases in terrain can actually help an ongoing tornadic thunderstorm to strengthen (Satrio, et. al 2020). A rapid rise in elevation can lead to a stronger updraft, while a rapid drop in elevation can help the rotating updraft stretch out, tighten, and rotate faster (Prociv, 2012).

A History of Tornadoes in Mountainous Terrain

Next, we will go over some notable tornadoes and tornado outbreaks in the mountains of the United States in chronological order, with a history of tornado forecasting and a public understanding of tornadoes also included. This is far from an exhaustive list, rather just a list of notable events.

Adirondack Tornado - 1845

Tornado data in more remote and mountainous terrain is limited the further back in time you look. However, one exception is a long-lived tornado in 1845 that tracked across Upstate New York, passing over the Adirondacks and Lake Champlain into Vermont. 

Appalachian Tornado Outbreak - June 23, 1944

A major tornado outbreak impacted communities in the Allegheny Mountains of Pennsylvania, Maryland, and West Virginia, resulting in at least 154 fatalities and over 1,000 injuries. The outbreak produced three F4 tornadoes and three F3 tornadoes.

The most notable tornado of this outbreak was an F4 that killed 100 people in West Virginia and destroyed the town of Shinnston. To date, this is the strongest and deadliest tornado on record in the state of West Virginia.

Tornado Awareness Increases - Late 1940s and 1950s 

Tornado research and awareness were limited until after World World II because the U.S. Weather Bureau (the "official" weather service in the U.S. before the National Weather Service) banned the use of the word "tornado" in forecasts, and discouraged research about tornadoes because it didn't want to cause public panic.

The lack of tornado awareness and tornado forecasts contributed to many fatalities from tornadoes prior to World War II and allowed for myths such as "tornadoes can't occur in mountainous terrain" to perpetuate. 

March 1948 was a turning point when a tornado hit the Tinker Air Force Base near Oklahoma City on the 20th of the month. Meteorologists who were in charge of weather forecasting for this base were caught off guard, and millions of dollars in damage occurred to aircraft on the base. However, these meteorologists noted the atmospheric conditions that were in place leading up to the tornado and began researching similar patterns in past tornado events.

Amazingly, just five days later on March 25, 1948, the Tinker Air Force Base meteorologists recognized a similar weather pattern in place compared to that of March 20. These meteorologists risked their jobs by issuing a tornado outlook based on pattern recognition, and sure enough, another tornado hit the base – except this time they were prepared.

This successful tornado forecast was a launching point toward tornado forecasting and awareness. The weather bureau officially began issuing tornado warnings in the 1950s. Tornado science, awareness, and documentation have steadily increased since then, along with a gradual realization that tornadoes can also occur in the mountains – even in the Rockies.

Shell Canyon, Bighorn Mountains, WY (F2) - June 26, 1959

This tornado took a 3-mile path across terrain between 9,000 and 10,000 feet in the Bighorn Range of North Central Wyoming, wiping out forested terrain near present-day Antelope Butte Ski Area. This was the first known mountain tornado to ever cause a fatality in the Western U.S. (Evans and Johns, 1996).

The track of the 1959 Shell Canyon tornado. Source: Midwest Regional Climate Center (https://mrcc.purdue.edu/gismaps/cntytorn#)

Several strong tornadoes (F2 or F3) have occurred in the Bighorn Mountains in the decades since the 1959 tornado. This is the furthest east significant mountain range in the Rockies and is in a better position to receive influxes of moisture originating from the Gulf of Mexico compared to other high ranges to the west. 

The April 1974 Super Outbreak 

One of the largest tornado outbreaks in U.S. history occurred in the East Central U.S., producing a total of 148 tornadoes including 30 tornadoes that were rated F4 or F5 which is a record for one day.

Most of the tornadoes on this day occurred west of the Appalachian Mountains, but several strong tornadoes penetrated deep into the Appalachians, busting the myth that mountainous areas and valleys in between mountains are "protected" from tornadoes.

Three F3 tornadoes occurred in the mountains of West Virginia and Virginia, while most notably, an F4 tornado occurred in the mountains of Southwest North Carolina, impacting the town of Murphy and causing a total of 24 injuries and 4 fatalities. 

Manitou Springs, CO (F3) - June 24, 1979

Colorado is known for frequent spring and summer tornadoes on the plains east of the I-25 corridor, but occasionally they happen in the mountains as well. In 1979, a strong tornado touched down above 7,000 feet near Manitou Springs before moving into the west side of Colorado Springs. This tornado produced F3 damage but only one injury occurred. 

The track of the 1979 Manitou Springs-Colorado Springs tornado. Source: Midwest Regional Climate Center (https://mrcc.purdue.edu/gismaps/cntytorn#)

May 31, 1985 Outbreak - Northeast U.S.

An intense tornado outbreak occurred in Eastern Ohio and Western Pennsylvania, with several strong to violent tornadoes moving through the Allegheny Mountains. The longest-track tornado in this outbreak was an F4 that was on the ground for 69 miles across the Alleghenies.

Tornado tracks during the May 31, 1985 tornado outbreak. Orange tracks indicate F3 tornadoes, red tracks indicate F4 tornadoes, and a single purple track near Youngstown, Ohio indicates an F5 tornado. Source: Midwest Regional Climate Center (https://mrcc.purdue.edu/gismaps/cntytorn#)

The Teton-Yellowstone, WY Tornado (F4) - July 21, 1987

The most extraordinary mountain tornado event on record occurred in the Teton Wilderness of Northwest Wyoming, near Grand Teton and Yellowstone National Parks. A violent high-elevation tornado cut a 24.3-mile path through this region with a damage path up to 1.6 miles wide at times, completely obliterating mature forests.

The damage path of the Teton-Yellowstone tornado in 1987, which was up to 1.6 miles wide at times. Photo: U.S. Forest Service / Andy Norman.

This tornado reached altitudes as high as 10,000 feet and even crossed the Continental Divide. To this day, this tornado holds the record for the strongest tornado to ever occur west of the Continental Divide, the strongest tornado in the state of Wyoming, and the highest elevation violent tornado (F4/EF4 or higher) to ever occur.

Fortunately, the tornado occurred in such a remote area that no injuries or fatalities occurred, though several campers and hikers were in the vicinity and reported strong winds and large hail, and heard the tornado's roar that "sounded like a freight train". 

Dr. Fujita studied the damage path of this storm extensively after the fact, noting that the tree damage surveyed in this storm exceeded that of more well-known violent tornadoes he had studied in the 1970s in Birmingham, Alabama, and Xenia, Ohio (Fujita, 1989).

Here is a graphic about the Teton-Yellowstone tornado that the National Weather Service office in Riverton produced:

Uinta Mountains, UT (F3) - August 11, 1993

Another impressive high-elevation tornado carved a 17-mile path through Northeast Utah. This twister reached a peak altitude of 10,880 feet, making it one of the highest-elevation strong tornadoes (F2/EF2+) on record.

The tornado approached a group of Boy Scouts that were setting up camp, but fortunately, the group was able to move to a safer location and no injuries occurred, though four vehicles in the area were damaged or destroyed (Dunn and Alder, 1994).

Great Barrington, MA (F4) - May 29, 1995

A violent tornado originating on the eastern side of the Taconic Range in Western Massachusetts killed three people and caused significant damage in the town of Great Barrington.

Researchers at SUNY Albany noted that the parent thunderstorm initially formed over the Catskill Mountains in New York and intensified as it moved downslope into the Hudson River Valley where a tornado eventually formed and produced F2 damage.

The first tornado dissipated as the storm neared the crest of the Taconic Range and the rotating updraft weakened. However, the storm intensified again as it moved down the east side of the Taconic Range and into Great Barrington, where a new tornado formed, producing F4 damage (Bosart, et al. 2006).

The tornado tracks across Eastern New York and Western Massachusetts on May 29, 1995. The first track in yellow on the left side of the image represents the first tornado that produced F2 damage on the west side of the Taconic Range. The second track in red on the right side of the image represents the second stronger tornado that produced F4 damage on the east side of the Taconic Range and in Great Barrington. Source: Midwest Regional Climate Center (https://mrcc.purdue.edu/gismaps/cntytorn#).

New York Tornado Outbreak - May 31, 1998

Just a few years later, another Northeast outbreak occurred which featured several F3 tornadoes that moved across the Catskills and Lower Adirondacks. One tornado was on the ground for 62 miles and passed just south of Binghamton before moving into the Western Catskills.

Salt Lake City, UT (F2) - August 11, 1999

This tornado dispelled two myths – 1) Tornadoes don't happen in the mountains and 2) Tornadoes don't happen in cities. On August 11, 1999, a strong tornado hit the downtown area of Salt Lake City, one of the largest cities in the Mountain West.

This tornado hit during the Outdoor Retailers Convention and killed one person at the event while causing a total of 80 injuries in the city and damaging or destroying 300 buildings.  

Photo: NWS Salt Lake City

The tornado formed at an elevation of 4,225 feet before lifting at 5,320 feet on the east side of the city in the foothills of the Wasatch Mountains. 

Full Recap – NWS Salt Lake City

The damage path of the Salt Lake City tornado in August 1999. Source: NWS Salt Lake City

Rockwell Pass, CA (F0) - July 7, 2004

This tornado, which formed in the High Sierra of Sequoia National Park, holds the distinction as the highest elevation tornado on record at an altitude of 12,156 feet. Backpacker Scott Newton photographed the tornado and captured debris being picked up and lofted (Monteverdi, et al. 2014).

The Rockwell Pass tornado. Photo: Scott Newton.

Arizona Tornado Outbreak - October 6, 2010

The mountains of the Southwest U.S. are not immune to tornadoes, either. This outbreak that occurred in Northern Arizona was the largest outbreak on record in the state, and also the largest outbreak on record west of the Continental Divide with a total of 11 tornadoes recorded. Most of these tornadoes occurred in the morning hours, which is unusual.

This event included three EF-2 tornadoes that tracked from south to north into the San Francisco Mountains near Flagstaff. The strongest tornado of the outbreak was an EF-3 which occurred northeast of Flagstaff on Cole Mine Mesa. 

The Super Outbreak of April 27, 2011

The first super outbreak occurred in 1974 and still holds the record for the most F4/EF4+ tornadoes in one day, but the second super outbreak of 2011 set the record for the total number of tornadoes in one day with 216. This outbreak also produced 15 tornadoes that were EF4 or stronger.

The geographic coverage of the 2011 super outbreak was similar to that of the 1974 outbreak but with more of a concentration in the Southeast. Numerous tornadoes impacted the Southern Appalachians, including several strong to violent tornadoes.

Two EF-1 tornadoes touched down in the vicinity of Mt. Rogers, which is the highest point in Virginia at over 5,000 feet. An EF-3 tornado caused significant damage in Glade Springs in Southwest Virginia, and multiple EF-3 tornadoes also occurred further south in the mountains of Tennessee and Georgia.

Most notably, an EF-4 tornado hit the western portion of Great Smoky Mountains National Park near the Tennessee/North Carolina border, causing significant tree damage.

Some of the most destructive tornadoes during this event occurred in the lower Appalachian foothills of Northeast Alabama, where terrain may have played at least somewhat of a role in the development and strength of these twisters.

Tornado tracks in the Southern Appalachian region during the April 2011 Super Outbreak. The strongest tornadoes occurred in the lower portions of the Appalachians and adjacent foothills, but weaker tornadoes also occurred in some of the higher-elevation terrain in the core of the Blue Ridge Mountains. Source: Midwest Regional Climate Center (https://mrcc.purdue.edu/gismaps/cntytorn#).

Mt. Blue Sky, CO (EF-0) - July 28, 2012

The second-highest elevation tornado on record in the United States occurred above treeline on the slopes of Mt. Blue Sky (formerly known as Mt. Evans) at an elevation of 11,900 feet. While not quite as high as the tornado that occurred in the High Sierra in 2004, this did set a record for the highest-elevation tornado in the state of Colorado.

Tornadoes in Other Mountainous Regions 

While this article primarily focuses on significant tornadoes that have occurred in the Appalachians, Rockies, and Sierra Nevada, tornadoes occur in other mountain regions of the U.S. and worldwide as well.

  • The Ozark Mountains are a small mountain range with its highest points in Northern Arkansas. This region is right in the middle of what is known as "Tornado Alley" and while they do not see as many tornadoes compared to neighboring Oklahoma or even central/southern portions of Arkansas, they do happen on occasion.

    In late May 2024, multiple EF-2 to EF-3 tornadoes impacted the mountain biking mecca of Bentonville, producing damage in and near the town, while significant damage was reported on the mountain bike trails in the area.

  • The foothills and lower portions of the Appalachians in Alabama and East Central Tennessee including the Cumberland Plateau are prone to tornadoes, and research has even suggested that local terrain features in these areas can enhance tornado development.

  • Northern New England (Vermont, New Hampshire, Maine) is no stranger to tornadoes either, and even the rugged White Mountains have experienced tornadoes on occasion. New England's most famous tornado occurred in Worcester, Massachusets in 1953, though this occurred east of the mountains. 
  • Mountainous terrain in the Great Lakes region of Northern Minnesota and Michigan experience infrequent but occasional tornadoes, though they are not as common compared to southern portions of these states where temperatures and moisture are typically more favorable for tornadic development. 

  • Across the Far Western U.S., cool season tornadoes (winter and spring) are not uncommon across the lower elevation ranges and central valley regions of California. 

  • The Cascades and Olympics in Washington and Oregon are the least tornado-prone mountain ranges in the Lower 48 with very few tornadoes noted in this area historically. However, the surrounding lowland and foothill areas outside of the Cascades (on both the east and west sides) occasionally experience tornadoes.

  • In Europe, several regions in the foothills of the Alps have been noted as relatively "favored" areas for tornadic thunderstorms. Also, the United Kingdom averages 30-50 tornadoes per year. 

Recent Significant Mountain Tornado Events

Tornadoes occur in the mountains every year, even in the higher-altitude Western U.S. We have written several in-depth articles on notable tornadoes that have occurred in the mountains in recent years.

Alan Smith, Meteorologist


References

Bosart, Lance F., Seimon, Anton, LaPenta, Kenneth D., Dickinson, Michael J., 2006. Supercell Tornadogenesis over Complex Terrain: The Great Barrington, Massachusetts Tornado on 29 May 1995. https://doi.org/10.1175/WAF957.1 

Dunn, Larry, Alder, William, McClung, Tim, 1994. The High Uinta Tornado. https://www.weather.gov/media/wrh/online_publications/TAs/ta9420.pdf 

Evans, Jeffry S. and Johns, Robert H., 1996. Significant Tornadoes in the Big Horn Mountains of Wyoming. https://www.spc.noaa.gov/publications/evans/bighorns.htm 

Fujita, T. Theodore, 1989. The Teton-Yellowstone Tornado of 21 July 1987. https://doi.org/10.1175/1520-0493(1989)117%3C1913:TTYTOJ%3E2.0.CO;2 

Monteverdi, John P., Edwards, Roger, Stumpf, Gregory J., 2014. An Analysis of the 7 July 2004 Rockwell Pass, California Tornado: Highest-Elevation Tornado Documented in the United States. https://doi.org/10.1175/MWR-D-14-00222.1 

Prociv, Kathryn A., 2012. Terrain and Landcover Effects of the Southern Appalachian Mountains on the Low-Level Rotational Wind Fields of Supercell Thunderstorms. https://vtechworks.lib.vt.edu/items/a85f7d5d-82f4-4249-86a0-c1f5c79ce264 

Satrio, Martin A., Bodine, David J., Reinhart, Anthony E., Maruyama, Takashi, Lombardo, Franklin T., 2020. Understanding How Complex Terrain Impacts Tornado Dynamics Using a Suite of High-Resolution Numerical Simulations. https://doi.org/10.1175/JAS-D-19-0321.1 

Schneider, Douglas G., 2009. The Impact of Terrain on Three Cases of Tornadogenesis in the Great Tennessee Valley. http://nwafiles.nwas.org/ej/pdf/2009-EJ11.pdf

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About The Author

Alan Smith

Meteorologist

Alan Smith received a B.S. in Meteorology from Metropolitan State University of Denver and has been working in the private sector since 2013. When he’s not watching the weather from the office, Alan loves to spend time outdoors skiing, hiking, and mountain biking, and of course keeping an eye on the sky for weather changes while recreating.

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