Two days of cirrus clouds moving in, followed by lowering bases and rain from nimbostratus clouds, with a warmer post-front temperature, indicate which type of front passed?

• A. Occluded Front
• B. Stationary Front
• C. Warm Front
• D. Cold Front

Answer: (C)

A warm front is passing. Cirrus clouds moving in ahead of a warm front are a telltale sign that warm air is beginning to overtake cooler air. As the front nears, the clouds thicken and lower, bringing steady, widespread precipitation from nimbostratus-type clouds as the warm air gradually rises over the cooler air. After the front passes, the air behind it is warmer, so you see a rise in temperature. This sequence—high cirrus followed by lowering, steady rain, then a warmer post-front air mass—fits a warm front perfectly.