It's a UP "K train" from Marion, AR to Oakland, CA. It typically enters California via Donner Pass in the early morning hours and shows up on Altamont Pass in the late afternoon. Its counterpart, the KOAMN, typically runs east on Altamont before/around noon on most weekdays and is on Donner in the early evening hours. That's all I know about the train; others on here might have even more specifics about it.