With a warm front approaching a cold front, which statement describes their interaction?

• A. The cold air mass remains stable with no weather changes.
• B. The warm air of the warm front passes over the colder more dense air of the cold air mass creating a relatively stable weather condition.
• C. The warm air slides over the cold air causing instability.
• D. The warm front stops at the interface and produces no significant weather.

Answer: (B)

When a warm front approaches a cold front, the lighter, less dense warm air slides over the cooler, denser air. This gentle ascent lifts the warm air over the cold air along a broad, sloping boundary, which tends to produce widespread, stratiform clouds and steady, lighter rainfall. That results in relatively stable weather compared with the more turbulent, convective conditions often seen with cold fronts. The statement that the warm air passes over the colder air creating relatively stable weather best describes their interaction.