A few strong early storms, and a late start to winter, is moving more water down the Columbia River dam system. Average hydro output in November is up 2GW over last year through the 13th of November. That surplus should diminish going forward, as normal rainfall and the beginning of snowpack begin to reduce the excess stream flow.
The 5 day NWS forecast for the lower Columbia River (at Vancouver) called for gradually increased flow, peaking on the 16th and declining slowly thereafter:
In California, the much smaller hydro capacity is also running well above last year's reduced levels. As we approach the halfway point in November, hydro output is averaging 1.9 GW, about 0.9 GW above the comparable 2015 period.
As California sees higher hydro, and imports much of the Pacific NW hydro surplus, it equates to 2GW of lower thermal generation:
.....and correspondingly higher power imports, which are up 1.1 GW in November thusfar:
Imports aren't up more because other renewables, primarily solar, are also elevated year-on-year. Wind is about the only renewable that is underperforming 2015 in the month of November. Overall, renewables represent +4% of power market share this year, rising from 21% to 25%.