The "conceptual storyline" of a lesson refers to the flow and sequencing of learning activities such that science concepts align and progress in ways that are instructionally meaningful to student learning of the concepts. Research demonstrates that when teachers apply lesson design strategies to create a coherent science content storyline, student learning is positively impacted (Roth et al., 2011). Because the conceptual storyline is often implicit within a lesson, and teachers often have difficulty articulating this aspect of lesson design (Lo et al., 2014), our professional development program engages elementary teachers in analyzing and developing graphic representations of a lesson's conceptual storyline to make that element explicit. In this exploratory study, we present typologies that represent two primary challenges teachers faced in developing coherent conceptual storylines in their lesson design, and examine the extent to which professional development enhanced their capacity to develop a coherent conceptual storyline.