A last-lap effort from Carlos Munoz was rewarded with pole position for this weekend's Indy Lights race at Edmonton.
Overnight rain left drivers facing a track that was still drying when they first left the pitlane, but positions changed constantly as the conditions improved and the lap times fell.
With the track at its best right at the end, Andretti Autosport's Munoz reeled off a 1m25.5115s lap in the final moments to displace Peter Dempsey, driving for Belardi, by just 0.03s.
Current points leader Esteban Guerrieri was third-fastest, with his Schmidt team-mates Tristan Vautier and Oliver Webb just behind him.
Webb had enjoyed a stint at the top of the screens with a lap in the 1m29s range 20 minutes before the end, but was unable to retain his advantage as the circuit dried.
Pos Driver Team Time Gap 1. Carlos Munoz Andretti 1m25.5115s 2. Peter Dempsey Belardi 1m25.5504s + 0.0389s 3. Esteban Guerrieri Sam Schmidt 1m25.7204s + 0.2089s 4. Tristan Vautier Sam Schmidt 1m25.8422s + 0.3307s 5. Oli Webb Schmidt 1m26.2155s + 0.7040s 6. Sebastian Saavedra AFS/Andretti 1m26.4777s + 0.9662s 7. Victor Carbone Sam Schmidt 1m26.6683s + 1.1568s 8. Gustavo Yacaman Moore 1m26.7651s + 1.2536s 9. Jorge Goncalvez Belardi 1m26.8487s + 1.3372s 10. Juan Pablo Garcia Jeffrey Mark 1m26.9077s + 1.3962s 11. David Ostella Moore 1m27.5362s + 2.0247s