Yamaha's Ben Spies beat championship contenders Dani Pedrosa and Jorge Lorenzo to top a wet second MotoGP practice at Aragon.
Like many of the other frontrunners, the American had elected to sit out the first session when the track was neither fully wet nor fully dry.
He was first out at the start of the second however, when all uncertainty about conditions had been removed by a brief but heavy shower.
Times fell consistently as the session developed, and in the final minutes top spot almost exclusively belonged to Yamaha's two works riders.
Lorenzo looked to have sealed it with the session's first sub 2m01s lap, but moments later Spies shaved a further five tenths of the Spaniard's benchmark to go top.
There was still time for Honda's Dani Pedrosa to sneak into second, just six hundredths of a second shy of Spies.
Lorenzo stayed third ahead of Ducati's Nicky Hayden, the last rider to get within one second of the ultimate pace.
Tech 3 Yamaha's Andrea Dovizioso were fifth and seventh, sandwiching the LCR Honda of Stefan Bradl.
Valentino Rossi on the second Ducati locked out ninth, ahead of satellite riders Karel Abraham (Cardion Ducati), Alvaro Bautista (Gresini Honda) and the second works Honda of Jonathan Rea.
Pos Driver Team Time Laps
1. Ben Spies Yamaha 2m00.219s 17
2. Dani Pedrosa Honda 2m00.285s + 0.066 16
3. Jorge Lorenzo Yamaha 2m00.746s + 0.527 15
4. Nicky Hayden Ducati 2m00.996s + 0.777 16
5. Andrea Dovizioso Tech 3 Yamaha 2m01.379s + 1.160 17
6. Stefan Bradl LCR Honda 2m01.626s + 1.407 14
7. Cal Crutchlow Tech 3 Yamaha 2m01.665s + 1.446 15
8. Valentino Rossi Ducati 2m02.412s + 2.193 15
9. Karel Abraham Cardion Ducati 2m02.632s + 2.413 19
10. Alvaro Bautista Gresini Honda 2m03.263s + 3.044 18
11. Jonathan Rea Honda 2m04.046s + 3.827 15
12. Randy De Puniet ART 2m04.353s + 4.134 15
13. Aleix Espargaro ART 2m04.423s + 4.204 15
14. James Ellison ART 2m04.542s + 4.323 14
15. Mattia Pasini ART 2m04.722s + 4.503 14
16. Yonny Hernandez BQR 2m04.858s + 4.639 16
17. Michele Pirro FFT 2m06.030s + 5.811 16
18. Hector Barbera Ducati 2m06.182s + 5.963 11
19. Danilo Petrucci Ioda-Suter 2m06.368s + 6.149 16
20. David Salom BQR 2m06.593s + 6.374 14
21. Colin Edwards Suter 2m06.677s + 6.458 13