Jason Bracken rushed for a touchdown and returned an interception for another as Prairie remained in the hunt for a playoff berth.
The Falcons (4-4, 2-2 in 3A Greater St. Helens League) will play at Kelso next Friday for the No. 3 seed from the 3A GSHL to the state preliminary round.
Bracken intercepted a pass on the first play from scrimmage in the game, which led to Denzel Hamiel's 30-yard touchdown reception from Tyler Armstrong on the next play.
After Fort fumbled on its next offensive play, Bracken's 20-yard reception set up Dallas Goodpaster's 3-yard TD run, and Prairie led 14-0 less than a minute into the game.
Bracken had a 38-yard touchdown run to put Prairie ahead 20-0 less than four minutes into the game.
Bracken's 63-yard interception return for a touchdown gave Prairie a 34-0 lead in the second quarter.
Brendan Bussey had a 24-yard fumble return for a touchdown and Kyle Schulson capped the scoring with a 53-yard interception return for a score.
PRAIRIE 54, FORT VANCOUVER 6
Fort 0 0 6 0 --6
Prairie 27 14 6 7--54
P--Denzel Hamiel 30 pass from Tyler Armstrong (Scott Keyser kick)
P--Dallas Goodpaster 3 run (Keyser kick)
P--Jason Bracken 38 run (run failed)
P--Goodpaster 6 run (Keyser kick)
P--Bracken 63 interception return (Keyser kick)
P--Brendan Bussey 24 fumble return (Keyser kick)
P--Hamiel 1 run (kick failed)
FV--Marquis Taylor 20 pass from Dakota Stowell (pass failed)
P--Kyle Schulson 53 interception return (Keyser kick)
RUSHING -- Fort Vancouver: Mitchell Cooper 7-36, Marquise Radford 8-33, Jordan Suell 5-17, Ben Brown 1-4, Miro Flores 1-0, Babacar Secka 1-(-2). Prairie: Bracken 2-48, Goodpaster 5-42, Hamiel 7-37, Ronnie Evenden 7-32, Bussey 3-20, Jordan Marti 1-6, Armstrong 1-(-4), Kevin Aguirre 1-(-10).
PASSING -- Fort Vancouver: Suell 8-19-2-52; Stowell 1-1-0-20.Prairie: Armstrong 9-10-0-85, Aguirre 0-2-0-0.
RECEIVING -- Fort Vancouver: Taylor 5-35, Stowell 1-23, Secka 3-14. Prairie: Bracken 4-50, Hamiel 1-30, Schulson 4-27.