Given the long-term nature of the UP closure, resulting from fire damage between Klamath Falls and Weed, Amtrak (as expected) has cancelled the Starlight north of Sacramento. This is basically what happened when UP closed the line for a bridge replacement in the Sacramento River canyon some years ago.
Quote:Amtrak web site
Coast Starlight Trains Canceled Between Seattle and Sacramento until mid-July
Friday, July 2, 2021 1:30 PM EDT
Amtrak Cascades Trains Provide Substitute Transportation Seattle-Eugene
Trains 11 & 14 are unable to operate between Seattle and Sacramento due to a temporary track closure by the Union Pacific Railroad. Until on or about July 14, these Amtrak Coast Starlight trains will operate only between Los Angeles and Sacramento.
Customers booked between Seattle and Eugene are welcomed aboard Amtrak Cascades trains. No other substitute transportation is available. Refunds are being provided.