Heat transfer measurements performed by Riedinger et al. (Phys. Fluids, 25, 015117 (2013)) showed that in an inclined channel, heated from below and cooled from above with adiabatic walls, the flow is laminar or intermittent (local bursts can occur in the laminar flow) when the inclination angle is sufficiently high and the applied power sufficiently low. In this case, gravity plays a crucial role in the characteristics of the flow. In this paper, we present velocity measurements, and their derived tensors, obtained with Particle Image Velocimetry inside the channel. We, also, propose a model derived from a jet interpretation of the flow. Comparison between experiment and model shows a fair agreement.