We present a case study of the formation of a small-scale vortex, which has been observed by the aircraft campaign AIRMETH2 in the delta of the Mackenzie River, Canada. AIRMETH2 was carried out in July 2012 with the purpose to measure methane concentrations over arctic wetlands, thereby also providing a high-resolution data set of meteorological quantities in the lower troposphere. While the observed vortex of about 50 km horizontal scale is not resolved in the ERA-Interim data, high-resolution WRF simulations with a mesh size of about 2 km can indeed model its formation. The aircraft observations are then used to validate the model results in the lower troposphere. It turns out that the position of the vortex in the model is somewhat shifted in comparison to the observed vortex. Other meteorological quantities are also compared. For example, we find deviations in the structure of vertical temperature profiles.