The Pirates will play the winner of Tuesday's match between El Camino and Grossmont.
Coach Travis Turner said the final four appearance is OCC's sixth straight.
Chris Van Vuuren had 12 kills and two service aces against Palomar.
John Christian, a Corona del Mar High graduate, recorded eight kills on nine swings.
Vanguard 6, La Sierra 0, five innings
RIVERSIDE — Stacie Salazar threw five shutout innings, striking out seven in the Lions' nonconference game, which was shortened at five innings due to lightning on Friday.
The second game between Vanguard (28-20) and La Sierra (7-30) was rained out.
Breanne Gomez went two for three with a run batted in, and Adriana Venezia went two for three.
The Lions' Golden State Athletic Conference game on Saturday at Azusa Pacific has been moved from noon to 3 p.m.
WOMEN'S WATER POLO
Vanguard (2-13) canceled its women's water polo match against Concordia because of the storm Friday.
Vanguard's Golden State Athletic Conference doubleheader at home on Saturday against The Master's College has been postponed because of the weather.
The Lions (18-16, 8-14 in conference) plan to play the first game at home on Monday at 3 p.m. and the second game is tentatively rescheduled at home on April 20 at 3 p.m.