When overrunning air is moist and stable, what weather is expected with a warm front?

When overrunning air is moist and stable, what weather is expected with a warm front?

• A. Light to moderate warm rain will occur over an extensive area, with frontal fog near the front.
• B. Heavy showers from cumulonimbus clouds.
• C. Only middle or high clouds are expected.
• D. No precipitation is expected.

Answer: (A)

Overrunning moist, stable air ahead of a warm front tends to produce widespread stratiform precipitation. As the warm air slowly slides over the cooler air, lifting is gentle and spread out, causing low- to mid-level cloud decks and light to moderate rain that covers a broad area. Frontal fog often forms near the front because the abundant moisture condenses when air near the surface cools. Heavy showers from cumulonimbus clouds come from stronger instability and vertical development, which isn’t present with stable overrunning. So, only mid- or high clouds would not bring this kind of widespread rain, and no precipitation would contradict the lifting and moisture in place.

Overrunning moist, stable air ahead of a warm front tends to produce widespread stratiform precipitation. As the warm air slowly slides over the cooler air, lifting is gentle and spread out, causing low- to mid-level cloud decks and light to moderate rain that covers a broad area. Frontal fog often forms near the front because the abundant moisture condenses when air near the surface cools. Heavy showers from cumulonimbus clouds come from stronger instability and vertical development, which isn’t present with stable overrunning. So, only mid- or high clouds would not bring this kind of widespread rain, and no precipitation would contradict the lifting and moisture in place.