Michael Stockbridge and Greg Bernash each had 18 points to lead Prairie, which clinched the No. 3 seed to the bi-district tournament.
The Falcons will play at Kennedy Catholic of Burien next Thursday in the double-elimination tournament.
Jordan Suell scored 12 to lead Fort, which had its season end with an 11-9 record.
PRAIRIE 65, FORT VANCOUVER 34
PRAIRIE — Jacob Davidson 5, Palmer Goecke 12, Koy Osborn 0, Michael Stockbridge 18, Seth Hall 6, Ethan Rouse 0, Walker Hausherr 2, Le 0, Brandon Crosby 2, Greg Bernash 18, Dwayne Stewart 2. Totals 23-46 (7-19) 12-17 65.