noun
strong local wind from the Hira mountains
A strong, cold downslope wind from the Hira mountains in Shiga Prefecture, known for causing rough conditions on Lake Biwa and disrupting the Kosei Line.
比良おろしが吹くと、琵琶湖の波が高くなる。
When the Hira-oroshi blows, the waves on Lake Biwa get high.
冬の比良おろしは湖西線の運行に影響を与えることがある。
The winter Hira-oroshi can affect operations on the Kosei Line.
颪 is a general term for a wind blowing down a mountain slope. 比良おろし is a specific local wind named after the Hira mountains.
From 比良 (Hira, the mountain range) + 颪 (oroshi, a wind blowing down a mountain).