Cook pasta in salted water until al dente. Drain and place in a large bowl to cool. 

Cook bacon in the oven at 400º for 25 minutes. Chop.

In a small bowl, whisk together the sour cream and ranch dressing. 

When the pasta has cooled, but is still warm, add green onions, cheese, and ½ of the bacon mix to combine. Pour dressing over the warm pasta and stir to coat the pasta. Refrigerate until ready to serve. 

Prior to serving add the remaining bacon to the top and serve cold or at room temperature.