Smoke pot and oil fog smoke tracers have been used to plan meteorological instrument placement and quantitatively estimate air volume flow from a tributary during nocturnal drainage wind conditions. The estimated volume flow agrees well with estimates of the flow using tethered-balloon and remotely obtained wind velocity measurements. The smoke visualization shows a very complex flow structure caused by tributary flow interactions with the flow down the main valley. The magnitude of the outflow volume from the tributary was greater than expected. If the tributary studied is representative of the other tributaries in the valley, most of the volume flow in the main valley may enter through the tributaries.