From the Weather Center
by John Simon
The website, boldmethod, defines a dry line as a boundary between moist and dry air masses. Unlike a cold or warm front, in the case of a dry line, one air mass is not rapidly overtaking the other. Additionally, the temperature on either side of a dry line will be similar, meaning there isn’t a large temperature gradient. The biggest difference in the two air masses lies in the moisture content of each.
A dry line will typically form north to south in the southern and central plains of the United States. We don’t see many of them in the northwest. In most cases, the dry line represents the boundary between the moist air that is drawn up from the Gulf of Mexico and the drier air that is blowing across the deserts of the southwestern United States northern Mexico.
Sometimes, you will hear a dry line referred to as a Maffa Front, after the town of Maffa, Texas. That is because this area commonly sees dry lines during the spring and early summer. The phenomenon is also fairly common up and down tornado alley.