I noticed the Goldstar icon wasn't on my station yesterday afternoon. I did a little digging and found an older post on WU regarding some insight into how they rate stations.
I can't figure out why my station would drop off the list. The only variance I see is temperature. Mine is actually slightly lower than surrounding stations due to being higher in elevation and in a valley area. Furthermore, it's in the shade most of the day. So thankfully, I'm not seeing a lot of sun related temperature spikes.