Extreme winters in Northern Hemisphere midlatitudes in recent years have been connected to declining Arctic sea ice and continental snow cover changes in autumn following modified planetary waves in the coupled troposphere-stratosphere system. Through analyses of reanalysis data and model simulations with a state-of-the-art atmospheric general circulation model, we investigate the mechanisms between Arctic Ocean sea ice and Northern Hemisphere land snow cover changes in autumn and atmospheric teleconnections in the following winter. The observed negative Arctic Oscillation in response to sea ice cover changes is too weakly reproduced by the model. The planetary wave train structures over the Pacific and North America regions are well simulated. The strengthening and westward shift of the Siberian high-pressure system in response to sea ice and snow cover changes is underestimated compared to ERA-Interim data due to deficits in the simulated changes in planetary wave propagation characteristics.