7/16/2015 Mt. Adams Complex Update A.M.

For nearly a week, the weather forecast by the incident meteorologist has predicted a fairly common phenomenon called a “subsidence inversion” for the Mt. Adams Complex.  It will likely occur tonight. 

This type of inversion develops when a widespread layer of air descends, compresses, and heats due to increasing atmospheric pressure.  These inversions typically occur at night and, as a result, temperatures increase and humidity decreases to 15-20 percent. During the dry period, lichens and small ground fuels dry out, leading to potential increased fire activity.

Firefighters at the Mt Adams Complex have been preparing for the impacts of the inversion by steadily mopping up the perimeters of the Riley and Horseshoe Fires and extinguishing hot spots identified by palm infrared (IR) heat-detection devices and IR flights. A spot fire near the Riley Fire has been contained.

Fire officials reported today that the Horseshoe Fire has been “put to bed” but they are monitoring it closely to observe its reaction to the inversion and increasingly warm weather predicted for next week.

On the Riley Fire, firefighters continue to mop up and monitor the fire activities from lookouts near the fire.  Initial attack crews are ready to respond to any new fires or spotting that might occur later today as winds produce gusts up to 30 miles per hour. Lower humidity and wind will increase interior consumption of remaining, unburned areas inside the fire perimeter.  Fire officials are confident that the mop-up of the fire perimeter will prevent the fire from growing larger.