GP3 championship leader Valtteri Bottas set the pace in free practice at Spa on Friday morning. The ART Grand Prix driver moved to the top of the times early in the session, and he was still there when the first rain shower of the weekend hit with 11 minutes remaining.
Shortly before the rain fell, Mitch Evans had been chipping away at the Finn's margin out front. He initially brought it down from 0.9sec to 0.6, and he chopped it down to 0.2sec with his final flying lap. James Calado was third in the second ART entry, just ahead of Adrian Quaife-Hobbs and Antonio Felix da Costa.
Nigel Melker had been Bottas's closest challenger early on, but he slipped to sixth while the times were improving.
Just behind him was Alexander Sims, who currently sits second in the championship. The Status Grand Prix driver was one of the few to stay out on slick tires when the rain initially fell, and he was only lapping nine seconds off the pace before the showers got heavier for the final couple of minutes.
Evans was one of the first to venture out on wet weather rubber, but he returned to the pits without completing a flying lap.
GP3 will not have a second practice session this weekend, as the circuit's noise curfew means the on-track action has to finish earlier than at other races. As a compromise, this morning's session was extended to 45 minutes instead of the usual half hour.