[en] Accurate measurements of plasma flows in the scrape-off layer (SOL) are a necessary requirement for understanding the physics of tokamak edge plasmas. A system is being developed on Alcator C-Mod for inferring flows parallel (v_paralleL) and perpendicular (v_ExB) to local magnetic field lines from impurity emission patterns ('plumes') generated by local gas injection. Carbon plumes are generated at variable location in the SOL by puffing deuterated ethylene gas (C₂D₄) through the end of a reciprocating fast-scanning probe. Two intensified CCD cameras are used to record C⁺¹ and C⁺² emission patterns simultaneously from near-perpendicular views. Plumes are modeled using a Monte Carlo impurity transport code, from which values for the background flows may be extracted. The sensitivity of the plume structure is investigated for a number of code inputs, including radial electric field (E_r) and the neutral launch dynamics. Initial modeling results indicate discrepancies between values of v_parallel and E_r extracted from the plumes and measurements obtained from probe data