Definition
Winds of approximately 20 to 40 knots blowing across mountainous terrain, strong enough to produce noticeable turbulence, updrafts on the windward side, and downdrafts on the leeward side, but generally not severe enough to create the violent rotors and mountain wave activity associated with stronger winds.
Plain English
Winds in the 20-to-40-knot range flowing over mountains. They are strong enough to bounce an airplane around and push it up on the side facing the wind and down on the far side, but they are not yet in the severe range where flying near the mountains becomes dangerous for most light aircraft.
Context Anchor
Used when planning or flying near mountains, especially when deciding how to approach ridges, passes, and valleys.
Derivation
“Moderate” comes from a root meaning “kept within measure.” In aviation weather, it means a middle level of strength—not calm, and not extreme. That helps because moderate mountain winds can still be strong enough to matter.
Why Pilots Care
These winds can cause unexpected altitude loss or gain near terrain and require pilots to fly higher and maintain extra airspeed margins.
Grounding Statement
Picture wind flowing across a ridgeline: the air may lift on one side and sink on the other, even when the wind is only moderate.
Intuition Check
Do not assume “moderate” means harmless. In mountain flying, moderate wind can still create turbulence, updrafts, and downdrafts near terrain.
Example Sentence 1
The forecast called for moderate mountain winds, so the pilot added 2,000 feet of clearance above the ridge and planned a 45-degree crossing angle.
Example Sentence 2
With moderate mountain winds forecast, we delayed departure until the afternoon convective activity had passed.