Meanwhile, relative low pressure develops to the south displacing the Azores high. This negative phase of the North Atlantic Oscillation often results in harsh winter weather over eastern North America and in Europe. The cold air pools and expands well to the south over the eastern United States. The storm track too is pushed south of normal resulting often in snowstorms for the eastern metropolitan areas. In Europe, the easterly steering flow beneath the North Atlantic blocking highs often draws cold air from Siberia west to replace the normal mild maritime air over western Europe.
Snow can accompany the unusual frigid winter temperatures.
When you hear of cold and snow in Europe, it is likely that the North Atlantic Oscillation has turned negative. These blocks are usually transitory and last on average a week or two. If conditions are right, the blocks redevelop again after a period of time. In some years, the negative phase of the NAO can repeat itself frequently. It is forecasted to continue mainly negative right into the winter.