obscuring phenomenon

In United States weather observing practice, any atmospheric phenomenon (not including clouds) which restricts the vertical visibility or slant visibility, that is, which obscures a portion of the sky from the point of observation.

Related terms:

• transparent sky cover
• precipitation ceiling
• summation principle
• prevailing visibility
• luminous meteor
• variable visibility
• indefinite ceiling
• clear
• obstruction to vision
• partial obscuration