Ioda-Suter CRT man Danilo Petrucci topped the first MotoGP free practice timesheet in a damp first session which saw only nine riders take to the circuit and only two prototypes putting in a flying lap.
The Italian went round in 1'43.178 and was only challenged by fellow CRT man Michele Pirro with both men out on slicks at session end while Britain's James Ellison bagged third with his last fast lap but was 2.5s down.
The Kendal man did do 15 laps in the slippery conditions and the presence of an Aprilia engineer in the PBM garage may indicate he is testing upgrades this weekend.
Former World Superbike grid-filler David Salom, who has replaced Ivan Siva, took fourth ahead of Ben Spies, Nicky Hayden, Yonny Hernandez, Mattia Pasini and Colin Edwards.
Repsol Honda new-boy Jonathan Rea did one lap to assess the conditions and thought better of it.