In the early hours of what most B.O. pundits describe as the start to better days at the domestic box office, 20th Century Fox’s 3D animated pic “Rio” is on track to win the weekend, ranging from $30 million to $33 million, according to pre-weekend tracking services. The Weinstein Co.’s “Scream 4,” via TWC label Dimension, should hit in the $23 million-range.“Rio’s” projected weekend take, which allows for some wiggle room as family films are famously hard to predict, is above what Fox says it’s expecting to collect for the toon, but in line with (if not somewhat below) rival studio projections. Meanwhile, “Scream 4″ is in the ballpark of Weinstein’s Thursday expectations at $24 million-$27 million range, but that depends on Friday’s late-night fanboy take. Still, if both pics come close to early expectations, that would mean overall weekend totals would likely be up from the same sesh last year, which saw top two players “Kick-Ass” and “How to Train Your Dragon” total just shy of $20 million. With potentially improved conditions this weekend, B.O. observers say the following two weekends should keep the ball rolling, starting with Fox’s “Water for Elephants” and Lionsgate’s “Tyler Perry’s Madea’s Big Happy Family” on April 22, followed by the much-anticipated “Fast Five” from Universal, on April 29. Then it’s off to the races with a summer sked chock full of high-profile tentpoles. Also opening this weekend us Roadside Attractions’ “The Conspirator” at 707 locations. It’s projected to open around $4 million for the weekend, which would give the film a good per-screen average considering its wider-than-usual berth.