Hector Barbera defied the worsening weather conditions and a brief fall to claim provisional pole position for the 250cc class at Brno.
With rain falling again as the riders returned to the circuit, it was clear that the most confident competitors would prevail as the weather continued to get worse over the course of the 45 minutes.
For the most part it was Marco Simoncelli that made the running, the Italian using his warm treaded tyres to increase his gap consistently and establish a fair lead over the opposition until around ten minutes to go when his rivals began to go faster.
Mika Kallio was the first to strike, the Finn hitting the top spot with eight minutes remaining when he produced a lap some five tenths faster than Simoncelli's, an impressive effort given the rain was falling heavily now and spray was being kicked up.
However, even he had no answer to Barbera's lap with just five seconds left on the clock, the Team Toth Aprilia rider snatching the initiative by six tenths of a second. He duly celebrated by falling off on his warm-down lap, although he was unharmed as he gingerly grazed the air barrier.
Simoncelli settled for third, ahead of Alex Debon, the Spaniard confidently setting good laps in the early stages but having to settle for a spot on the outside of the front row.
Hiroshi Aoyama was fifth, with Mattia Pasini sixth, although the big plaudits must be saved for Eugene Laverty, who proved exactly what he can do when the field is levelled out by claiming a provisional seventh on the grid. With more rain forecast for tomorrow, he has a good chance of holding onto that spot.
Julian Simon, local rider Lukas Pesek and Alvaro Bautista rounded out the top ten, the latter experiencing a heavy off in the closing stages.
First qualifying – Brno
1. Barbera (Aprilia) 2mins 16.210secs
2. Kallio (KTM) +0.686secs
3. Simoncelli (Gilera) +1.096secs
4. Debon (Aprilia) +1.549secs
5. Aoyama (KTM) +2.738secs
6. Pasini (Aprilia) +2.876secs
7. Laverty (Aprilia) +3.586secs
8. Simon (KTM) +3.778secs
9. Pesek (Aprilia) +3.945secs
10. Bautista (Aprilia) +4.060secs