Cloud base

[golmayobolibar]

Is cloud base layer measured AGL or AMSL??? Important for VFR flights...

[Gkikas LGPZ]

@golmayobolibar

As you can see, over The Alps, cloud base is forecast 100ft,
so the cloud base is AGL.
More precisely:
It is "above the level of the model orography". So principially it is AGL, but be aware of ECMWF model resolution which is 9km, i.e. terrain is sampled with 9km step. So if you are in mountainous terrain, you can not rely on it, do not use it for planning in such cases.