Of all the air mass types, which are of greatest significance to the United States and Canada? What happens to them as they migrate to locations different from their source regions? Give an example of...

Of all the air mass types, which are of greatest significance to the United States and Canada? What happens to them as they migrate to locations different from their source regions? Give an example of air mass modification.

How does the lifting of an air mass affect the weather? Discuss the association of lifted air masses with precipitation and condensation.