The automation of business processes is of vital importance for organizations to speed up their business and to lower costs. Due to emerging technologies in the field of Internet of Things, changing situations can be recognized automatically, which provides the basis for an automated adaptation of process executions in order to react to changing circumstances. Although approaches exist that enable creating self-adapting workflows, a systematic modelling approach that supports the specification of situational dependencies directly in workflow models is missing. In this paper, we tackle this issue by presenting a modelling extension called SitME that defines (i) an extensible Situation Event type, (ii) the concept of Situational Scopes, and (iii) a visual notation. As the introduced extension is language-independent, we apply the approach to BPEL to validate its practical feasibility.