obstruction to vision

In United States weather observing practice, one of a class of atmospheric phenomena, other than the weather class of phenomena, which may reduce horizontal visibility at the earth’s surface; examples are fog, smoke, and blowing snow.

Related terms:

• indefinite ceiling
• fog scale
• vertical visibility
• obscuring phenomenon
• prevailing visibility
• obscuration
• luminous meteor
• partial obscuration
• variable visibility
• obstruction moraine