While radar is a generally reliable method to detect and display moisture-bearing clouds, it is not foolproof and can generate false-returns or "ghost" images under certain conditions.

These conditions occur sporadically around the country when radar is being reflected off some large geographic feature like a mountain or can even be caused by man-made structures and equipment such as a wind farm. 

In mountainous terrain such as found in the state of Colorado such issues are more likely to occur, and unfortunately this is a physical location problem that cannot be fixed.

<Click> here for additional information: 5 Things Radar Can't See.