Do Barn Owls in Southern California prey on cats?

I want to know if barn owls (in San Diego County) will prey on a large cat? I keep hearing one outside my house nightly, making a skretching noise a hour or so after dark. Whenever I hear the noise, I notice that my cat is coming down a hill and into our home for the night (he stays out all day in a wooded area behind our home). I think my cat is about 11-13 lbs, is he at risk?