full text of the classic FAA guide
AIR MASSES AND FRONTS
Why is weather today clear and cold over Oklahoma while it is warm and moist over Alabama? What caused the line of thunderstorms that you circumnavigated over eastern Arkansas? Air masses and fronts provide the answer. You can better plan the safety and economy of flight when you can evaluate the expected effects of air masses and fronts. This chapter explains air masses and fronts and relates them to weather and flight planning.