Seattle has had a nearly identical slowdown, so perhaps not entirely due to California emigration... although the water is muddy - reportedly people are exiting Seattle for greener pastures as well.

I have a theory that a major portion of the population in Seattle is always churning. Lots of people moving in and out (Like a college town). But if they can’t get people to keep moving in, you end up getting huge deflation.

The weather is a shock to lots of people.

I just sold my house in Seattle and will be leaving next month.

Seattle may be a revolving door, but the main reason people are leaving is because they can't afford it, so they move out to the boonies, and commute.

Despite that, it is having an unprecedented net population boom.