Cook the pasta in salted water until al dente. Drain, rinse with cold water, and shake off the excess.

Whisk the mayonnaise, sour cream, buffalo sauce, vinegar, garlic powder, salt, and pepper until smooth.

In a large bowl, combine the cooled pasta, chicken, celery, carrot, and half the blue cheese. Pour the dressing on top and fold until evenly coated.

Cover and refrigerate for at least 30 minutes. Stir, then top with the remaining blue cheese and sliced green onions just before serving.