The annual rains can be both a welcome old friend and a bitter enemy. Heavy monsoon rainfall in the region will continue this weekend through the start of the week, bringing with it both life-giving moisture for the parched earth and the threat of more damaging flash flooding.
Widespread monsoon moisture spreads across the West through the weekend, northward into Oregon, Washington, Idaho, Wyoming, and Colorado.
Strong thunderstorms bearing heavy rainfall, lightning, and gusty winds are possible across the region. Although the moisture could help improve drought conditions, the risk of flash flooding is high.
Flash flood watches are scattered across half a dozen western states on Sunday due to heavy rainfall continuing through the early part of the week.
Heavy rainfall spread up the Rockies into southwestern Wyoming, through much of Idaho and eastern Oregon on Saturday. Arizona, Nevada, and the far eastern parts of California expect to see up to an inch of rainfall through the weekend.
On Sunday, the region of the strongest storms shifts northward, stretching up through eastern Washington and parts of Montana. A new area of concern develops Sunday over New Mexico and western Texas.
The rain is crucial for the Pacific Northwest where fires have plagued the area throughout the summer amid historic drought conditions and multiple record-breaking heat waves.
Battling fires in the Northwest
The US currently has 87 large fires burning over 1.7 million acres of land, 23 of which are in Idaho. Montana is also feeling the strain of fire season with 21 large active fires. California and Oregon are experiencing extreme fire conditions, with the country’s two largest fires growing to consume hundreds of thousands of acres.
The monsoon moisture moving into the region this weekend could potentially stomp out some fires and quench the dry vegetation and soil, but it could also cause more dangerous conditions.
Red flag warnings are in place across central and eastern Oregon for the weekend, where the potential for thunderstorms has drawn out worries for more fire starts. The Bootleg Fire in the region has already blistered over 400,000 acres of the Oregon hills, and lightning and strong winds from monsoon thunderstorms could start more fires, further straining resources.
The rainfall might help control some fires in the region. But left behind will be the scorched earth that is prone to runoff and flash flooding.
Flash flooding on the scarred hills
Saturday, heavy rain is forecast to impact Colorado once again, where mudslides already blocked off a major interstate on Friday, leaving 100 people stranded in their vehicles.
The burn scars left behind are especially susceptible to the dangers of heavy rainfall, even years after the wildfire has been extinguished.
Burnt soil is extremely repellent to water absorption, acting more akin to pavement than a sponge. This can spell bad news in terms of flash floods.
Even areas far downhill and downstream from burned regions can see the effects of flash flooding and experience debris flows because of the water adverse nature of the scarred areas.