Place the chicken breasts in the bottom of the slow cooker.
Add the carrots, celery, onion, garlic, thyme, bay leaf, salt, and pepper on top of the chicken.
Pour in the chicken broth and water.
Cover and cook on low for 6 hours.
Remove the chicken, shred it with two forks, and return it to the slow cooker.
Add the egg noodles and cook for 20 more minutes on high until the noodles are tender.
Stir in the fresh parsley just before serving.