West Coast-Barcelona $340+
Looks like UA is running a random Nonstop to Barcelona from SFO on 27FEB and prices are pretty low from the west Coast.
SAN-BCN $523
https://goo.gl/flights/rnsgD
SFO-BCN $397
https://goo.gl/flights/bXm2M
DEN-BCN $522
https://goo.gl/flights/6cJz9