September 2, 2015: NE Washington fires, seasonal fire danger trends and smoke.

The cool and cloudy (even rainy) conditions we've seen so far this week will likely become drier, bringing potential for a little more smoke for the NE Washington Area, though not likely at the same scale as we saw last week.

How do we know this? Now is a good time to review what's driving the fire activity behind this smoke. One of the key metrics used to understand and track fire danger is called Energy Release Component or ERC. ERCs are basically a metric for how hot a fire can burn (the total available energy that could be released if the vegetation were burned by the flaming front of a fire).  The ERC can serve as a good characterization of fire season as it tracks seasonal fire danger trends well.  For Kettle Falls, roughly in the middle of the area where we have been tracking smoke, the recent rain has taken us from above 20 year historic highs, to below average ERC values:

Note however, that forecasted (green line) ERC values are heading back up again--though we are likely past the seasonal ERC peak, there are hundreds of thousands of acres within the perimeters of these fires. In many of these areas internal to the fire perimeter, there is still lots of heat being generated, especially where big logs in the heavy timber still smolder, over 1000's of acres.

The scale of these fire is going to be a big factor persistence of their smoke impacts:  If you straightened out the perimeter of the Northstar fire into a line stretching out to the southeast for example, that line would extend over 185 miles, nearly to Spokane!

VIIRS, the new high resolution satellite system that can detect heat from fires, shows (yellow dots) where heat was last detected in the past 6 days...These are the areas that could potentially produce more smoke if things warm up again, even if the perimeters of the fires don't expand further:

This pattern repeats across the other fires in the area too.  Here are the same graphics for the Kettle and Okanogan Complexes*.