The Potential for Large Grass Fires in Eastern Washington this Summer
There is a serious wildfire threat in eastern Washington right now, with a growing potential for large, fast-moving grass fires.
For this threat to be realized, all it will take is strong winds and some careless ignition.
I found huge amounts of annual grasses when I took a drive to
Thorp, Washington on Saturday. Worrisome.
Ironically, the key setup was the cool, moist spring we just completed, which led to bountiful grass production east of the Cascade crest.
The wonderful USDA Forest Service website fuelcast.net shows the situation clearly. Below is a map of the current amount of annual herbacious plant material (such as annual grasses) in our region (I secured this from fuelcast).
Substantial fuel amounts over the Columbia Basin and the eastern slopes of the Cascades, with large areas with more the 700 pounds per acres. That is a lot of fuel for fire.
Very dangerous.
The danger was realized last week when someone started a large grass fire near Prosser (the Byron Hill Fire) that incinerated over 4000 acres (see picture below). Fireworks ignited the fire.
The Byron Hill Fire
The threat is rapidly worsening now as the huge amount of grass/annual vegetation rapidly dries and "cures"--- a normal process that was delayed by the cool, wet weather. With dry, warm summers, grasses are generally ready to burn by middle to late June in eastern Washington.
One can track the drying process by looking at graphs of dead fuel moisture available from the U.S. RAWS weather stations around the U.S. Many measure 10-h dead fuel moisture for small diameter fuels (a diameter less than one inch).
As a rough rule of thumb, 10-h dry fuel moisture below 10% is a dangerous fire threat. And it only takes roughly a day of dry weather to make such fuels a problem...that is why they are called 10-h fuels.
Below is the 10-h deal fuel moisture from the YTC-RC site northeast of Yakima for the past 90 days. The 10-h fuel moisture goes up and down due to short rainy period, but during the dry spell in late June it dropped below 6%!
The message is clear. With the huge amount of grasses in place now curing (drying out) and fuel moisture dropped to under 10%, there is a large threat.
And for this threat to be realized, we need some ignition source (e.g., fireworks, trash burn, cigarettes, target practice sparking on a rock, lightning, failing electrical infrastructure).
But to get a fast-moving grass fire you also need wind. And wind we can forecast with great skill.
For eastern Washington, there are two major wind situations to keep in mind. The first is the strong northwesterly winds that descend the eastern slopes of the Cascade slopes, particularly during the afternoon and early evening. There is a reason there are a lot of wind turbines just east of the Cascades!
Such winds are particularly strong during periods of unusually cool weather in western Washington after on onshore marine push.
And then there are the powerful winds associated with high pressure building to the north and northeast. Such winds are particularly frequent and strong during late summer. Such as event occurred during September 7-8, 2020, and resulted in a fast-burning fire that destroyed the eastern WA town of Malden (see below)
Malden Washington
Whitman Country Sheriff's Office
Time to Act is Now
With such an acute wildfire threat, anyone living near large expanses of grass should clear several hundred feet of safe space around their residence. You should be ready to evacuate quickly, any time strong winds are forecast.
The state needs to be constantly monitoring the winds and warning people when strong winds are predicted. And the state needs to ready fire fighting capabilities for such events.
Of course, folks need to be very careful about not starting fires. Utilities need to ensure no branches hang over power lines and be read to de-energize powerlines in vulnerable locations.
Some advanced planning could help ensure that another Malden disaster does not occur this summer.
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