Final answer:
Traveling over a colder region increases an air mass's stability, reducing the likelihood of thunderstorms and leading to clearer skies.
Step-by-step explanation:
As an air mass travels over a region that is much colder, its stability will increase and there will probably be clear skies.
When an air mass travels over a colder surface, it tends to cool down from below, leading to a stabilization of the air mass. This increased stability inhibits the upward convection of air that is typically associated with the formation of thunderstorms. Therefore, the air mass becomes less prone to the development of intense storm activity and is more likely to result in clear skies. Stability in the atmosphere is a key factor in determining weather patterns, such as precipitation and storm events.