(a) General rule.--Except as otherwise provided in section 5424 (relating to temporary emergency jurisdiction), a court of this Commonwealth which has made a child custody determination consistent with section 5421 (relating to initial child custody jurisdiction) or 5423 (relating to jurisdiction to modify determination) has exclusive, continuing jurisdiction over the determination until:
(1) a court of this Commonwealth determines that neither the child, nor the child and one parent, nor the child and a person acting as a parent have a significant connection with this Commonwealth and that substantial evidence is no longer available in this Commonwealth concerning the child's care, protection, training and personal relationships; or
(2) a court of this Commonwealth or a court of another state determines that the child, the child's parents and any person acting as a parent do not presently reside in this Commonwealth.
(b) Modification where court does not have exclusive, continuing jurisdiction.--A court of this Commonwealth which has made a child custody determination and does not have exclusive, continuing jurisdiction under this section may modify that determination only if it has jurisdiction to make an initial determination under section 5421.