Why might this trans-pacific flight not follow a more direct route? I notice that this flight from DFW to PVG has a path that’s not a single arc of a great circle. Rather, it looks like it flies to some city in California and then takes a direct route for the remainder.

Why might it do that, instead of following a more direct route, such as a great circle route?  It didn’t stop along the way, so why would it need to overfly an intermediate location that’s not on the direct route?

(flightaware.com) American Airlines 127 Thursday 04-May-2017

Compared to great circle route:

(gcmap.com)
Looks like they were avoiding a storm system from Oregon north into Canada.