Five minutes into the session, the weather interrupted proceedings and the riders used the remaining time for wet practice ahead of Sunday’s two races.
WFR Honda man Lowes’ two flying laps put him top ahead of championship leader Josh Brookes of Suzuki with a time of two minutes and 11.902 seconds.
Buildbase BMW pair Barry Burrell and Peter Hickman were third and fifth respectively while Chris Walker (Pr1mo Bournemouth Kawasaki) rounded out the top five in fourth.
Shane Byrne (Rapid Solicitors Kawasaki) completed one single lap and Tommy Hill (Swan Yamaha) had to settle for 11th-fastest thanks to the change of conditions.
Free practice one times:
Alex Lowes (WFR Honda) 2m:11.902s
Josh Brookes (Tyco Suzuki) +0.017s
Barry Burrell (Buildbase BMW) +0.157s
Chris Walker (Pr1mo Bournemouth Kawasaki) +1.915s
Peter Hickman (Buildbase BMW) +2.729s
Jakub Smrz (Splitlath Redmond Aprilia) +2.768s
Luke Quigley (GBmoto Honda) +2.781s
Michael Laverty (Samsung Honda) +2.995s
Karl Harris (Quattro Plant Kawasaki) +3.566s
Alastair Seeley (Tyco Suzuki) +3.839s
- Josh Brookes