Once you check in, you'll be able to see the waitlist so then you'll have a much better idea than anyone can give you.

I have found that, as a silver, it's been quite a mixed bag. I've been shut out when I thought I had a good shot and upgraded when I thought I was out of the running. Last year I was upgraded once. This year I am probably hovering around 15%.

This week I was 2/2 on upgrades including scoring PHL-DEN when I was 4th on the waitlist with one seat available. Two weeks ago, I ended up 14th for an ORD-PHL flight that I was upgraded on twice in the last 3 months.

How you find out depends on when you find out. On PHL-DEN, I found out I was upgraded on the United iPhone app with Passbook installed. I received an alert that said "Your seat is now 3F". A couple of times, I've checked my status on the app and saw "United First" on my boarding pass.

My guess is that you will find out at the airport. My advice is to prepare your backside to sit in coach. If you are upgraded, then celebrate your good fortune.