@gmahan3
The graphical profile shows the relative humidity aloft.
Heights for bases and tops come directly from the model.
Please keep in mind that cloud bases refer to "ceiling".
According to ECMWF: Ceiling is an output parameter that gives the height, above the level of the model orography,
of the base of the lowest cloud layer covering more than 50% of the sky (more than 4 oktas).
For definitions of ECMWF's forecast parameters:
https://confluence.ecmwf.int/display/FCST/Forecast+products+-+news+and+changes