PFPX and Runway Selection

 

How / when does PFPX select the preferred or optimum runway based on weather conditions? I have the weather option turned on and I understand how PFPX planning works. However, at what point does the "automatic selection" occur? Is it when I first enter the airport identifier into the route planner, ie. the first runway option displayed is the preferred one? 

 

Greatly appreciated if someone could point it out. 

 

Stephen