Question 1277Navigation General

The correct answer is A) high cirrus clouds gradually changing to cirrostratus and then to altostratus. The first indications of a warm front's approach are high, thin cirrus clouds that gradually thicken and lower into cirrostratus and then altostratus clouds. This cloud progression is a key indicator of a warm front moving in, as the high cirrus clouds are followed by the thicker, lower-level cloud types associated with the warm air mass advancing over the region. The other options are incorrect because they describe different weather patterns not specifically associated with the initial signs of a warm front's approach. Option B describes thunderstorms, option C describes fog, and option D describes low clouds and rain, which are later stages of the warm front's passage rather than the first indications.