With a threat of rain on both Thursday and Friday, teams face the prospect of having to condense much of their final on-track preparations of the season into only two full days of dry running over the weekend.
And with the temperatures over the weekend expected to be cold, this will inhibit chances of getting on top of the 2013 Pirelli control tyres in representative conditions ahead of the Australian Grand Prix.
This follows the first Barcelona test being held in conditions that Mark Webber described as the "worst-case scenario" for the tyres, and in which all teams struggled with degradation.
So far, most of the eight days of testing have been largely unaffected by rain, but low temperatures have skewed the tyre picture.
During the upcoming final four days of running, the 11 teams are expected to bolt on their final Melbourne-specification upgrades and conduct race simulations.
Much attention will be focused on McLaren, which has shown encouraging form in the first two pre-season tests but has hit the headlines this week following technical director Paddy Lowe's decision to switch to Mercedes next year.
Jenson Button admitted at the last test that the team still has work to do in understanding the McLaren MP4-28, meaning that making the most of track time at Barcelona could be key to the team starting the season strongly.
Ferrari is also expected to bring some development parts, with Fernando Alonso confident that he can fight for the world championship provided that it is possible to "improve the car a little bit.
Red Bull is set to bring more parts for its evolutionary RB9 machine, while Lotus, which has shown a good turn of speed so far this year, could also continue to try out its passive DRS concept.
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