1. Descriptive of a sky cover of 1. 0 (95% or more) when at least a portion of this amount is attributable to clouds or obscuring phenomena aloft; that is, when the total sky cover is not due entirely to surface-based obscuring phenomena. In aviation weather observations, an overcast sky cover is denoted by the symbol “symbol”; it may be explicitly identified as thin (predominantly transparent); otherwise a predominantly opaque status is implicit. An opaque overcast sky cover always constitutes a ceiling. See obscuration. 2. Popularly, the cloud layer that covers most or all of the sky. It generally suggests a widespread layer of clouds such as that considered typical of a warm front.