There is currently a severe wildfire threat east of Washington, with the potential for large, fast-moving grass fires increasing.
For this threat to materialize, all it takes is strong winds and some careless ignition.
I found a large amount of annual grass when I drove up
Thorp, Washington on Saturday. Worrying.
Ironically, the key setup is the wet spring we just finished, leading up to Grass production is abundant on the eastern side of the Cascade Peak.
USDA Forest Service’s Great Website fuelcast.net shows the situation clearly. Below is a map of the annual amount of pathogenic plant material (such as annual grass) in our area (I have ensured this from the fuel broadcast).
Significant amounts of fuel over the Columbia Basin and the eastern slopes of the Cascades, with large areas at more than 700 pounds per acre. That’s a lot of fuel for the fire.
What is unusual about accumulating “fuel” every year? The following image from fuelcast.net shows the deviation from the normal for the vegetable fuel, with the contour showing the Columbia River Basin. Some areas near Yakima and the eastern Cascade ridge have more than 200% of normal vegetation (such as annual grass)
The danger was realized last week when someone started a large grass fire near Prosser (Byron Hill Fire) that burned more than 4000 acres (see image below). Fireworks ignite the fire.
Byron Hill Fire
The threat is getting worse as the huge amount of annual grass/vegetation quickly dries out and “cures” — a normal process that has been delayed by cool, humid weather wet. With warm, dry summers, grass is usually ready to burn in mid to late June in eastern Washington.
One can monitor the drying process by looking at dead fuel moisture charts available from US RAWS weather stations across the US Many people measure 10 hour dead fuel moisture for fuel small in diameter (less than one inch in diameter).
As a general rule, a 10-hour dry fuel moisture content of less than 10% is a hazardous fire threat. And it only takes about a day of dry weather to make such fuels a problem… that’s why they’re called 10-hour fuels.
Below is the 10-hour agreed fuel moisture content from the YTC-RC site northeast of Yakima over the past 90 days. The 10-hour fuel moisture content rose and fell due to a short period of rain, but during the dry spell at the end of June, it dropped below 6%!
Clear message. With large amounts of grass in place now curing (withering) and fuel moisture dropping below 10%, there is a major threat.
And for this threat to materialize, we need some source of ignition (e.g. fireworks, burning trash, cigarettes, rock-fired spark targets, lightning, electrical infrastructure failure) .
But for a grass fire to burn quickly you also need wind. And the wind we can forecast with great skill.
For eastern Washington, there are two high wind scenarios to watch out for. The first is strong northwesterly winds that sweep down the eastern slopes of the Cascade, especially in the afternoon and early evening. There’s a reason why there are so many wind turbines just east of the Cascades!
Such winds are particularly strong during periods of unusually cool weather west of Washington after the sea pushes inland.
And then the extreme winds combined with high-pressure build-up in the north and northeast. Such winds are especially frequent and strong in late summer. For example, the event that occurred on September 7-8, 2020 and resulted in a rapidly burning fire that consumed the town of Malden in eastern WA (see below)
Malden Washington
Whitman . National Sheriff’s Office
The time to act is now
With such a severe wildfire threat, anyone living near large lawns should clear a few hundred feet of safe space around their residence. You should be ready to evacuate quickly, whenever strong winds are forecast.
The government needs to regularly monitor the winds and warn people when strong winds are forecast. And the state needs to have ready firefighting capabilities for such events.
Of course, people need to be very careful about not starting fires. Utilities need to make sure there are no branches hanging from power lines and are read to disconnect power lines in vulnerable locations.
Some advanced planning can help ensure that another Malden disaster doesn’t happen this summer.
