Boil a large pot of salted water. Add elbow macaroni and cook for 7-9 minutes until al dente. Drain and rinse under cold water.

In a medium bowl, whisk together mayonnaise, whole milk, brown sugar, apple cider vinegar, Dijon mustard, salt, and black pepper until smooth.

In a large bowl, combine cooled macaroni with grated carrots, yellow onion, celery, and green onions.

Pour dressing over the macaroni and vegetable mixture. Gently toss until evenly coated.

Cover and refrigerate for at least 30 minutes to allow flavors to meld.

Before serving, toss gently and garnish with additional green onions if desired.