1. In a large pot, melt butter over medium heat. Add carrots, celery, and potatoes. Cook until vegetables are tender, about 10 minutes.
2. Stir in flour and cook for 1-2 minutes. Gradually add chicken broth, stirring constantly until smooth.
3. Add chopped pickles, pickle juice, and dill weed. Bring to a boil, then reduce heat and simmer for 20 minutes.
4. In a small bowl, mix sour cream with a bit of hot soup to temper it. Stir the sour cream mixture back into the soup. Season with salt and pepper to taste.