[katu.com]
"Washington crews have never seen tumbleweeds like this...
we haven’t had this before, but I guess we’ll just figure it out.”

It doesn't seem like much of a puzzle.
What they were not saying in that media article: In the last 20 years there were major fires in 2019, 2016, 2007, and 2000.
Since tumbleweeds propagate much faster than native sagebrush, especially after a fire, this has left the area with
more tumbleweeds to blow around than normal.

Also, cattle, sheep, horses, and goats eat tumbleweed before it goes to seed (but to a very minor extent so do elk and deer).
Since a large portion of this area is a nature reserve and The Hanford Nuclear Site, there is no leasing of the land for
animals that can overgraze the area or have an effect on eating enough tumbleweed for control. So, left to their own devises,
tumbleweeds have won near Rattlesnake Mountain.

I drive Highway 240 about a half a dozen times every year and I was in one of the tumbleweed storms in 2019, but it wasn't
anywere near as severe as the one on New Year's, but still had to slow down. Another first for me in 2019 was seeing the elk
herd crossing the highway over to the Hanford area. Some of the herd had stopped and were looking back
at the stragglers that hadn't gotten across the highway yet. That slowed the traffic down too!

References:
[www.tri-cityherald.com]

[www.mnn.com]
"A government botanist sent to investigate in the early 1890s could barely believe his eyes: "One almost continuous
area of about 35,000 square miles has become more or less covered with the Russian thistle in the comparatively
brief period of twenty years."

[www.wsdot.wa.gov]
"Wildlife crossing underpass on SR 240 that provides access to habitat in the vicinity of McNary National Wildlife Refuge"

[www.sagegrouseinitiative.com]
[www.usu.edu]