Tire Choices for this year

Last year's pole lap:
The weather is expected to be cloudy, very humid, with the possibility of light rain come Saturday, the ambient temperatures and conditions will be very similar to testing, so lap times should be similar. They probably won't be because we'll see who's made progress and who hasn't as Barcelona is usually when teams bring their first upgrade package of the season.
The weather is going to favor the soft tire towards the end of the race especially if it remains cloudy throughout the day, the medium will still be the perferred race tire. It's been a weird year weather wise, it's usually much warmer this time of year in Barcelona. The hard tire will essentially be useless as it's no more durable than the medium tire, but with less grip. Most teams will do a two stopper, although a very aggressive three is possible
Here are the 2016 best testing times on the soft tires
1. Kimi Raikkonen, Ferrari, 1:23.009, Test Two, Day Three
2. Nico Rosberg, Mercedes, 1:23.022, Test Two, Day One
3. Felipe Massa, Williams, 1:23.193, Test Two, Day Three
Medium tires:
2. Lewis Hamilton, Mercedes, 1:24.133, Test Two, Day Four
1. Nico Rosberg, Mercedes, 1:24.126, Test Two, Day Three
3. Sebastian Vettel, Ferrari, 1:24.611, Test Two, Day Two
This probably tells a more accurate picture, with Mercedes being on average about half a second per lap faster than Ferrari. It's close, and hopefully though not realistically, it'll be a smaller gap this weekend.