Seen 3 stationary large bright strobing lights in the sky behind clouds

We were driving home from Sandy Oregon heading west on Hwy 26 when my wife noticed these 3 bright strobing white lights in the sky to the south of us. As we drove by them they seemed to have had no beam as event or search lights and they didn't seem to be attatched to anything but they strobed and stayed the exact position apart. We stopped to the side of the hwy and I got out to video tape them. There was no sound. I didn't stay recording long enough to see if they ever came out from behind the clouds. In the video you can see an airplane go by underneath or in the distance. I posted this on WTF in Gresham on Facebook and others commented about seeing them too and couldn't figure what they were.