This is the 9820th most frequent Japanese word.
覆う
To cover; to overlay.
Here, '覆う' is used to describe physically covering the entire mountain with snow.
大雪が山全体を覆っている。
Heavy snow is covering the entire mountain.
In this example, '覆う' is used metaphorically to indicate obscuring or veiling a secret.
秘密を覆うベールが徐々に解けていく。
The veil covering the secret is gradually being lifted.
This usage of '覆う' metaphorically depicts filling or surrounding the town with a specific emotional state.