Crews are fighting the Sourdough wildfire, caused by lightning in North Cascades National Park in Whatcom County, just a few miles north of Diablo Dam on the upper Skagit River.
The fire has spread across about 25 acres, the National Park Service (NPS) reported Monday, July 31. Early estimates put the fire at just 15 acres on Sunday, July 30, but more accurate mapping helped the NPS determine the full extent of the blaze. Between Sunday and Monday, NPS reported minimal fire spread.
The fire was initially detected Saturday, July 29, but may have started earlier in the week, NPS public information officer Katy Hooper said Monday.
“We had a storm system come through last Wednesday with a lighting storm pattern,” Hooper said.
Hooper said that storm caused several small fires, including two Pyramid area fires. The Sourdough fire was detected days later, but was most likely caused by the Wednesday lightning storm.
The fire continues to burn due to warm temperatures, windy conditions and low humidity throughout the area, according to a Sunday NPS news release.
Park officials closed the Sourdough Mountain Trail — leading to a historic fire lookout — while U.S. Forest Service firefighters combated the blaze on the ground.
That historic fire lookout, one of the oldest in the park, is not currently threatened, Hooper said.
“The lookout is about 2 miles from the fire,” she said Monday afternoon. “There’s no infrastructure threatened at this time.”
On Sunday, four helicopters and six Fire Boss scooper planes delivered water to support the groundwork.
“Overall, aerial operations have successfully kept the fire in check when able to fly,” according to the Sunday NPS release.
Aerial operations were suspended for 45 minutes Sunday, when unauthorized drone flights near the fire posed “a significant safety risk.” As a result, NPS said, the fire spread during the temporary halt.
A type-1 hotshot crew will begin fighting the fire Monday, July 31, as dry, windy conditions continue.
In the meantime, the Washington State Department of Transportation has asked curious drivers not to pull over along state Route 20 near the Diablo Lake Dam. While the road remains open, they ask visitors to “keep in mind your safety and those of first responders and do not pull over to take photos or deploy drone aircraft,” the department tweeted Sunday.
Sourdough and Pierce Mountain camps are closed due to the Sourdough fire, according to NPS. Access across Diablo Dam is limited to Skagit Tours, Ross Lake Resort and North Cascades Environmental Learning Center reservation holders only.
Campfires or the ignition of wood, briquettes, or any fuel in fire pits, fire pans, and barbeque grills are banned in all portions of North Cascades National Park. This includes all National Park Service lands and campgrounds along state Route 20, as well as Hozomeen and Stehekin Valley.
Rangers at North Cascades National Park were not immediately available for comment.
On Monday, several fires were burning across Washington state, including the Eagle Bluff Fire in Okanogan County. The fire, which began Saturday, July 29, spread from just 2,500 acres Saturday to an estimated 10,000 acres on Monday, and is burning sage and scattered timber while threatening homes, crops and infrastructure.
Communities on both sides of the U.S.-Canada border have been evacuated as a result, including Osoyoos in British Columbia. A level 2 “get ready” evacuation notice has been issued for residents along Highway 97.