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/Bike Time Gap 1. Ben Spies Yamaha 2m00.219s 2. Dani Pedrosa Honda 2m00.285s + 0.066s 3. Jorge Lorenzo Yamaha 2m00.746s + 0.527s 4. Nicky Hayden Ducati 2m00.996s + 0.777s 5. Andrea Dovizioso Tech 3 Yamaha 2m01.379s + 1.160s 6. Stefan Bradl LCR Honda 2m01.626s + 1.407s 7. Cal Crutchlow Tech 3 Yamaha 2m01.665s + 1.446s 8. Valentino Rossi Ducati 2m02.412s + 2.193s 9. Karel Abraham Cardion Ducati 2m02.632s + 2.413s 10. Alvaro Bautista Gresini Honda 2m03.263s + 3.044s 11. Jonathan Rea Honda 2m04.046s + 3.827s 12. Randy de Puniet Aspar Aprilia 2m04.353s + 4.134s 13. Aleix Espargaro Aspar Aprilia 2m04.423s + 4.204s 14. James Ellison Paul Bird Aprilia 2m04.542s + 4.323s 15. Mattia Pasini Speed Master Aprilia 2m04.722s + 4.503s 16. Yonny Hernandez Avintia FTR-Kawasaki 2m04.858s + 4.639s 17. Michele Pirro Gresini FTR-Honda 2m06.030s + 5.811s 18. Hector Barbera Pramac Ducati 2m06.182s + 5.963s 19. Danilo Petrucci Ioda Suter-BMW 2m06.368s + 6.149s 20. David Salom Avintia FTR-Kawasaki 2m06.593s + 6.374s 21. Colin Edwards Forward Suter-BMW 2m06.677s + 6.458s