Dry Lines
What about boundaries between air masses of different humidity? Known as dry lines, or dew point fronts, these weather fronts separate warm, moist air masses found ahead of the dry line from hot, dry air masses found behind it. In the U.S., they’re most often seen east of the Rocky Mountains across the states of Texas, Oklahoma, Kansas, and Nebraska during spring and summer. Thunderstorms and supercells often form along dry lines, since the drier air behind them lifts up the moist air ahead, triggering strong convection. On surface maps, the symbol for a dry line is an orange line with semi-circles (also orange) that face toward humid air.