Final answer:
A relative humidity of 50% at Grouse Mountain represents a comfortable humidity level for most people, as it is a moderate value that is neither too high nor too low.
Step-by-step explanation:
When looking at a numerical weather prediction (NWP) pressure-level map, if the relative humidity at the level of Grouse Mountain is around 50%, it indicates that the air at Grouse Mountain is at a moderate or comfortable humidity level. Relative humidity is a measure of how much water vapor is present in the air compared to the maximum amount of water vapor that air can hold at a given temperature. It does not necessarily mean the air is 'dry' or 'humid' in the typical sense of how we experience humidity. A relative humidity of 50% is generally considered comfortable for most people.