If overrunning air is moist and unstable, which weather feature dominates a warm front?

• A. Cumulonimbus
• B. Cirrus
• C. Stratus
• D. Cirrostratus

Answer: (A)

Moist, unstable air tends to rise vigorously, creating strong convection. When air overruns a warm front, it’s lifted over the cooler air ahead of it. If that lifting air is both moist and unstable, those upward motions intensify and clouds grow vertically into tall cumulonimbus towers. Cumulonimbus clouds are the hallmark of deep convection and can bring heavy rain and thunderstorms, so they naturally dominate the weather in this scenario. High, wispy cirrus or the smoother cirrostratus indicate approaching systems but don’t reflect this level of vertical development, and low, blanket-like stratus suggests more uniform, steady precipitation rather than convective storms.