Buttermilk Ranch Dressing with Greek Yogurt

1 cup plain nonfat Greek yogurt

¼ cup low-fat buttermilk

¼ cup light sour cream

½ teaspoon dried parsley

½ teaspoon dried dill weed

½ teaspoon onion powder

¼ teaspoon garlic powder

¼ teaspoon salt

⅛ teaspoon ground black pepper