Yes, it's possible as I've gotten upgraded on that route when I was silver a few years ago. However, as with most (all?) upgrades, the probability is greatly dependent upon the day and time of the flight as well as the equipment. IIRC, US has a 767 on that route for one of the flights. That has 18 F seats so I would say odds of getting the UG on that flight on an off day (not sunday/monday or thursday/friday) would be pretty good. Of course, YMMV.