Since its 3.3 release, Modelica offers the possibility to specify models of dynamical systems with multiple modes having different DAE-based dynamics. However, the handling of mode changes by the current Modelica tools is not satisfactory. An important difficulty is the occurrence of impulsive behavior at some mode changes, for some variables. In this paper, we propose a compile-time algorithm for identifying such impulsive behaviors and quantifying them in terms of their magnitude orders. Such algorithm can be used as an additional step of the structural analysis of Modelica models.