What do high-altitude cirrus clouds generally indicate?

High-altitude cirrus clouds generally indicate the presence of warm fronts approaching and potential weather changes. These clouds are thin, wispy, and formed at high altitudes, typically above 20,000 feet. Their appearance suggests that moisture is being transported aloft, which is a characteristic feature associated with warming atmospheric conditions.

When cirrus clouds are observed, it often signals that a warm front is on the way, as they can precede the frontal boundary. This means that changes in the weather are likely, including temperature increases and the possibility of precipitation, as the warm, moist air begins to rise over the cooler, denser air ahead of the front.

Identifying these clouds is crucial for pilots and meteorologists because they serve as an early warning system for changing weather patterns. Thus, the presence of high-altitude cirrus clouds is a clear signal that pilots should be prepared for potential shifts in atmospheric conditions, making option B the correct choice.