NWS provider file for Weather Monitor plugin - (NWS = National Weather Service)

There is no standard set of weather terms used by the major providers (most of whom, incidentally, use the NWS as THEIR provider).

There is however a standard set of meteorlogical phenomena that observers report:

http://www.met.tamu.edu/class/METAR/metar-pg9-ww.html

Any other terms used are derived from these and the lower cloud level.