Display Screen or a Portion Thereof with a Graphical User Interface

The FIGURE is a front view of a display screen or a portion thereof with a graphical user interface for a snow groomer of one embodiment of our new design.

The lighter-toned shaded portions in the drawings illustrate portions of the display screen or portion thereof with a graphical user interface that forms no part of the claimed design. The outermost broken lines in the drawings show a display screen or portion thereof, and form no part of the claimed design. The remaining broken lines in the drawings show portions of the graphical user interface that form no part of the claimed design.