Which of the following conditions is reported as an obscuration?

Obscurations refer to weather phenomena that significantly reduce visibility in the atmosphere. Both heavy fog and dust or sandstorms qualify as obscurations because they create conditions where visibility can be dramatically restricted.

Heavy fog reduces visibility by suspending tiny water droplets in the air, which scatter light and create a thick haze. This condition can lead to very low visibility, often less than a quarter of a mile, impacting safe travel and navigation.

Similarly, dust or sandstorms consist of particulate matter that is lifted and suspended in the air, causing a significant reduction in visibility. This effect can be severe, as particles can obscure landmarks and hinder vision for drivers and pilots.

Recognizing both heavy fog and dust/sandstorms as obscurations is important for reporting and safety purposes, which is why the correct answer encompasses both conditions.