Winter Weather Brings Winter Wildfire, Burn Flows to Western US

Winter wildfires and burn flows are a possibility in the Western US as long as the winter weather lasts.

Once a wildfire has been put out, the threat remains. Another risk associated with winter storms is the potential for sudden and fatal debris flows in nearby communities due to burn scars left over from the massive summer fires.

The soil-sealing wax released by burning trees and other plants makes the ground almost water-resistant across a burn scar. Burned land is devoid of vegetation, but its roots cling to the ground and prevent soil erosion.

Heather Brinkmann a meteorologist from FOX Weather, said that In areas where the wildfire burned for a while, the soil subsequently acts almost as a water repellent. Rainfall that would typically be absorbed will run off quickly, especially in dense forests, and pose a threat of extreme flash flooding for everything down the mountain.

In addition to destroying trees and their roots, fire also leaves behind a large number of tree trunks that are easily gathered by flash flooding to form a debris flow.

According to the USGS, a debris flow can be caused by as little as 0.3" of rain within 30 minutes while a region is having its first post-fire burn. Recovery from a burn scar might take several years. In the first two years following a fire, debris flows are most common.

Burn Scars

The foothill communities near the burn scars in the Cascade Mountains experienced thunderstorms and heavy rain during the first of a series of powerful storms. Residents were warned at town hall meetings by community leaders.

At the meeting, an emergency manager expressed concern about road blockage caused by fire debris that tumbles down from hillsides. During the fire, firefighters nearly lost their lives.

A hazardous winter could be in store for millions of people due to widespread fires in Western states. The Northwest may experience a wetter-than-average year with more atmospheric river-fueled storms this winter because meteorologists are already predicting that a La Nina weather pattern will be in charge.

This summer served as a preview of what might occur if heavy rain falls on burn scars, with a debris slide wrecking a restaurant as it swept through with 7 feet of mud, boulders, and tree trunks. A burn scar in southern California experienced monsoon rain.

Higher Burn Severity, Higher Debris Flow

Daniel Horton, a professor of Earth and Planetary Sciences from Northwestern University, said that the hazard levels for debris flow are closely correlated with both the size and severity of a burn area. Higher burn severity equals higher risk from debris flow. The affected downstream areas are larger than the burn area.

New Mexico's largest wildfire in history has a burn scar that was also covered in monsoon rains this summer. The water supply of an entire town was contaminated by debris flows and runoff.

As a mixture of water and boulders, dirt, trees, sand, and everything else in its path, debris flows are described as a "slurry" by Horton.

Horton said Debris flows can be fatal if people are unable to flee and are very dangerous, as there has been known to destroy homes, roads, and other buildings. Debris flows can move at up to 35 mph.

US Landslides

According to the US Geological Survey, landslides kill 25 to 50 Americans on average each year and cost up to $2 billion in property damage. In January 2018, one of the worst burn flows occurred in Montecito, California. It resulted in the deaths of 23, injuries of 167, and the destruction of over 400 homes. It rained heavily in the upscale Santa Barbara County neighborhood where the Thomas Fire burn scar is located.

Brendan McClusky, the director of King County, Washington Emergency Management, said in an interview with FOX Weather that they are concerned now and will continue to be in a few years about the rain and the winter.

NOAA All-Hazards Weather Radio

The management assigned people to deliver information door to door, and they are now also providing them with NOAA all-hazards weather radios. For experts to precisely track the rates of rainfall, they will even set up a few portable weather stations on the summit of the mountain.

According to the Teton County website, a nationwide radio station network known as NOAA All-Hazards Weather Radio (NWR) broadcasts continuous weather reports from the closest National Weather Service office. Every day of the week, including holidays, NWR broadcasts official watches warnings, forecasts, and other hazard information from the Weather Service.