Advice from a Whitefish lawyer: What if I want to move with my children?

In Montana, a parent is required to give the other parent 30 days notice before making a move that will "significantly affect" the other parent's contact with the children.

Notice is required by certified mail or by personal service, and then proof of service is to be filed with the court.  A proposed revised plan will also be filed with the notice.  Ask your family law lawyer for further details.

Obviously, even if you move to the house down the street, the other parent should know about the move.  The other parent should always have your current address, and should know where their child is living when their parenting time is with you.

Thirty days notice gives the other parent time to respond and ask the court to change parenting plan.
My advice is to not leave the state of Montana with your children without giving written notice to the other parent or obtaining the other parent's consent.  You could be held in contempt of court, and can be fined and imprisoned.