Plain English Meaning

It's the weather advisory that tells pilots where the cloud bases are low, where visibility is poor, and where mountains are hidden in clouds or haze.

Full Definition

AIRMET SIERRA is the specific AIRMET issued for instrument flight rules (IFR) conditions and mountain obscuration. It warns of widespread ceilings less than 1,000 feet and/or visibility less than 3 statute miles affecting more than 50 percent of an area at one time, and of mountain passes or ridges obscured by clouds, precipitation, or haze.

Context Anchor

You will see AIRMET SIERRA during a preflight weather briefing, especially when planning an through of , poor visibility, or .