The Ursus Fire, burning in the south of the Bob Marshall Wildnerness, saw significant growth this week, growing by more than 60 times its size since early Monday morning.
The Ursus Fire initially reported on Aug. 25, is burning on the south side of Rapid Creek at the base of Ursus Hill. As of Wednesday, it has burned an estimated 1,824 acres.
The lightning-sparked fire is in the Bob Marshall Wilderness on the Spotted Bear Ranger District.
The fire is spreading to the east; it has crossed the Continental Divide near Observation Pass and a few spots have been observed on Helena-Lewis & Clark National Forest.
According to Inciweb, the Ursus Fire has reached the 2012 Elbow Pass burn scar, which should act as a buffer to slow the spread of the fire in that direction.
A point/zone protection strategy will be implemented by the Spotted Bear Ranger District to protect both the Danaher and Basin Administrative Cabin sites and to prevent the spread of the wildfire outside of the Wilderness.
Personnel from the Spotted Bear WFM were inserted into the area on Friday, September 2, and were joined by two Smokejumpers from Missoula on Tuesday, September 6. They have begun structure protection operations by installing sprinklers and wrapping buildings at the Danaher Administrative Site.
Due to the rapid growth of the fire as well as some gusty to strong winds, especially aloft in the atmosphere, a large smoke plume has been emitted towards the east-northeast; the smoke was visible on Tuesday in Choteau, Fairfield, Augusta, and Great Falls. There were also reports of some ash falling out of the sky in Augusta and Vaughn.
Strong winds on Wednesday will likely spur the fire to continue growing, which means that it will continue to emit a lot of smoke, which may cause the air quality to worsen in some locations.
The wind on Wednesday will be coming out of the west-southwest, so the smoke will be emitted toward the east and northeast. A wind shift on Thursday will then send the smoke plume toward the south and southwest.