Per this source:
the cut line for the U.S. Open is top 60 and ties, plus players within 10 shots of the lead.
Unless things change drastically and soon, 10 shots from the lead will be a top 10 score of minus 1. (of the players who are done playing today, Phil Mickelson is 12 shots off the lead -- he is 14th best of players in the clubhouse).
Therefore, it will be top 60 and ties. The cut line currently is +3, where 20 guys are tied for 48th. If the cut is +3, I would project that by the end of the day there will be only 60 or 61 guys at that figure. Makes for some quicker play over the weekend at least!