They cite inventories
Citi is the latest to raise GDP estimates for GDP in the 2Q. They now see the quarters growth at 2.9% vs 2.5% previous (their prior estimate).
They cite inventories for the jump saying that they will add 0.9% to the Q2 growth. It subtracted 1.1% in Q1.
US GDP will be released at 8:30 AM ET tomorrow.