Display Screen or Portion Thereof with an Animated Graphical User Interface

FIG. 1 is a front view of a display screen or portion thereof with an animated graphical user interface showing a first image in a sequence according to the new design; FIG. 2 is a front view thereof showing a second image in the sequence; FIG. 3 is a front view thereof showing a third image in the sequence; FIG. 4 is a front view thereof showing a fourth image in the sequence; FIG. 5 is a front view thereof showing a fifth image in the sequence; FIG. 6 is a front view thereof showing a sixth image in the sequence; and, FIG. 7 is a front view thereof showing a seventh image in the sequence. The outermost rectangular broken line in the figures illustrates a display screen or portion thereof and forms no part of the claimed design. The dash-dot lines in the figures indicate boundaries of the claimed design, and form no part thereof. The remaining broken lines represent elements of the graphical user interface that form no part of the claimed design. The appearance of the animated graphical user interface sequentially transitions from FIGS. 1 - 7 respectively. The process or period in which one image transitions to another image forms no part of the claimed design.