I know this question has been asked by many General Aviation pilots who fly small airplanes, but not clearly answered I think.

If I am flying to an airport like Denver, which sits at 5000' above sea level, should I adjust the "altitude" slider to 5000' in order to figure out the wind predictions on the surface of that airport or should I leave that slider at "surface" setting?

So please let's clear this issue for once and all...

As a pilot I check the windy app and while NAM and ECMWF and GFS reporting 4kt winds on the surface, ACTUAL winds were 12kt and gusting to 16kt.

Are those data on your app presented as an estimate or just a wild guess or actually based on something ? Because it is very different than the reality out there.