In a slow cooker, combine the onion, celery, carrots, garlic, lentils, cumin, oregano and chipotle peppers.
Stir in the vegetable broth, diced tomatoes and adobo sauce.
Cook on LOW until the lentils are tender, 8 to 10 hours. Transfer 3 cups of the soup to a blender and let cool for about 15 minutes. Add the avocado to the blender and puree until the mixture is almost smooth. Pour the mixture back into the slow cooker. Stir in the lime juice and parsley.