This year has seen at least five atmo-river events, perhaps more. Two hit during and after Veterans day, and thus we endured a week with 10 inches of rain poured on our roof.
Portland was hammered with over 2½" of rain yesterday while we had about half that. Today's storm hit Portland with an inch of rain then lifted to focus on a zone between Scappoose (two siblings & a neice live in that area) and our place - a persistent yellow-gold radar echo has been in place for a few hours now, with Portlandon the ragged southern edge of the rain shield. As I type at 9:45 our rain gage is at 3.11" and climbing at about .2" per hour, and it's expected to continue in a similar pattern overnight.
A Quick Fact from the ESRL website: On average, about 30-50% of annual precipitation in the west coast states occurs in just a few AR events, thus contributing to water supply.
And from Wikipedia: Atmospheric rivers are typically several thousand kilometers long and only a few hundred kilometers wide, and a single one can carry a greater flux of water than the Amazon River!