‘Extreme’ risk of dangerous fires in West amid record heat, lightning
A dangerous combination of hot, dry weather and severe thunderstorms is expected to create volatile conditions for Western wildfires on Wednesday.
While the record-shattering heat is enough on its own to send fire danger soaring, a mix of fire-weather ingredients is converging on a zone from Northern California to the Pacific Northwest and the Northern Rockies.
Nick Nauslar, a fire meteorologist with the National Interagency Fire Center, tweeted that Wednesday “will feature just about every fire weather threat the atmosphere can offer.” He emphasized that it “will probably be the fire weather day of the year with expected substantial growth on existing wildfires and emerging new large fires as well.”
Strong, shifting winds, dry thunderstorms and continued searing heat are expected to contribute to significant fire danger.
The outlook for Wednesday calls for “extremely critical” fire weather – the most severe category – in northwestern Montana, as well as “critical” conditions into Idaho, Oregon and Northern California, along with a widespread threat of dry lightning.
The fire weather forecast will also overlap with a severe thunderstorm threat – a rare combination, according to Nauslar.
Red flag warnings for dangerous fire weather cover the interior Pacific Northwest, much of Idaho and Wyoming, all of Montana, and parts of the northern Plains.
According to the Weather Service’s Storm Prediction Center, the dangerous conditions are the result of an unstable atmosphere ahead of a passing cold front, as this week’s heat dome is partially broken down by a strengthening Pacific trough, or dip in the jet stream. Extreme conditions are expected to continue through the afternoon ahead of the fast-moving cold front, which will arrive after dark.
The stormy setup could spawn pyrocumulonimbus clouds – or fire-generated thunderstorms – over existing wildfires, while lightning over bone-dry vegetation could easily ignite new fires. Gusty thunderstorm outflow winds and increasing straight-line wind also could spread fires rapidly.
“Recent fire activity indicates that fuels remain highly receptive across the region and will support critical lightning-driven fire weather concerns,” the Storm Prediction Center warns.
On Tuesday, lightning may have ignited the Mosquito Fire in the Sierra foothills in Northern California near the community of Foresthill. That fire grew rapidly overnight in dense forest and is threatening structures and power lines in the area. The fire’s growth is a testament to the parched fuels as well as the weather, with temperatures remaining in the 90s in parts of the Sierra foothills last night. The National Interagency Fire Center issued a fire behavior advisory Friday for Northern California, warning of “long range spotting, rapid fire growth, and high resistance to control.”
Farther south, the Radford Fire is burning over a ridgeline toward Big Bear, the popular ski resort area in Southern California, while the deadly Fairview Fire nearby continues to spread near the town of Hemet.
The National Interagency Fire Center on Tuesday moved to Preparedness Level 4, meaning that different regions are competing for firefighting resources, with several large and complex wildfires burning at the same time, such as the Sturgill Fire in Oregon and the Moose Fire in Idaho.
Any new major fires in the coming days could mean a move to Preparedness Level 5, the highest level, which has “the potential to exhaust national wildland firefighting resources.”
A 2020 study found a 25-day increase in the annual number of days with widespread fire danger and fire activity in the western part of the country, a figure that is projected to double by 2051-80.
“Climate change may continue to overburden fire management efforts across the region, requiring careful strategy when fire resources are strained in future dangerous, prolonged fire seasons,” the authors note.