PHOTOS: Tree struck by lightning that sparked Forsyth Fire

WASHINGTON COUNTY, Utah (ABC4) — The cause of the Forsyth Fire was confirmed as lightning on Monday, and the U.S. Forest Service shared photos of the tree struck by lightning that ignited the fire.

U.S. Forest Service Dixie National Forest shared the photos on social media with additional information about the early stages of fighting the Forsyth Fire and how lightning caused it.

During the Initial Attack (IA) on the fire on June 19, the IA Incident Commander found a tree struck by lightning close to the point of origin in the Pine Valley Wilderness Area. During the investigation, IA crews analyzed data that showed a thunderstorm moving through the area on June 9 and found “a visible lightning strike near the origin on a steep, rocky slope of the wilderness area.”

Inspecting the tree found that lightning struck the base of the tree and fire ignited within the trunk.

The Forest Service said that lightning strikes like this cause immense heat, which then vaporizes the sap and moisture inside the tree, igniting the wood from within. This creates a “slow, flameless form of combustion” called smoldering.

Smoldering can continue within the tree for extended periods of time, even days or weeks, without a visible flame, which was the case with the Forsyth Fire. The fire spread when winds picked up during the Red Flag warning on June 19, and the winds caused increased fire activity and made the smoke visible.

According to the Forest Service, IA crews responded quickly as soon as smoke was reported, but the favorable conditions for the fire–high temperatures, extremely low humidity, and high winds– caused it to move even faster towards the Pine Valley community.