The Yamaha-backed Australian, riding with a bruised right hand, set a time of 1min 41.416secs to top the timesheets.
The next ten riders were all within one second, headed by Gianluca Nannelli (Hannspree Honda Althea) and Jonathan Rea (Hannspree Ten Kate Honda), who had been quickest in the morning session.
Another British rider, Craig Jones of Parkalgar Racing Honda, was next up, followed by Angel Rodriguez of Yamaha Spain, who is substituting for David De Gea.
Points leader Joan Lascorz and Fabien Foret, both of whom had been session leaders early on, eventually slipped to seventh and ninth respectively.
WSS first qualifying - top 10:
1. Parkes (Yamaha)
2. Nannelli (Honda) +0.352secs
3. Rea (Honda) +0.441secs
4. Jones (Honda) +0.545secs
5. Rodriguez (Yamaha) +0.576secs
6. Roccoli (Yamaha) +0.617secs
7. Lascorz (Honda) +0.763secs
8. Veneman (Suzuki) +0.808secs
9. Foret (Yamaha) +0.842secs
10. Harms (Honda) +0.844secs
24. Walker (Kawasaki) +2.344secs
25. Gowland (Honda) +2.443secs
28. Coghlan (Honda) +3.356secs
