I was walking between buildings at work enjoying the night sky, about 8:50. I noticed a small group of 3 orange lights that I at first thought were airplanes moving north to south, just above the tree line. They were coming into view from behind a large building. As I watched, I noted more and more of them, about 20 - 30 in all. They moved slowly from north to south, in a band about 1-2 degrees wide that took about 2 - 3 minutes to pass. As they moved south over the Columbia river, all the lights slowly went out. They did not fall or drift, but were in a controlled, level pattern. There were slight variations in relationship to one another so I am certain they were not one large craft, although it is possible that there was a large craft in the midst since there were too many to closely observe all of them. I walked to the far side of the building to look south around a large tree and they were no where to be found. I did see most of them slowly fade out. These objects were the color of the orange lamps used on the freeways. They did not alarm me but they are not anything I have seen before. These should have been in radar range of Portland International Airport (PDX).