The potential roles of both external forcings and internal coupled ocean-atmosphere processes are considered. While the late winter variability is not found to be closely connected with external forcings, it is found to be strongly related to the internally generated component of Atlantic Multidecadal Variability (AMV) in Sea Surface Temperatures (SSTs). In fact, consideration of the seasonality of the jet stream variability within the winter months reveals that the AMV variability is far more strongly connected to jet stream variability during March than the early winter months or the winter season as a whole. Reasoning will be put forward for why this connection likely represents a driving of the jet stream variability by the SSTs, although the dynamics involved remain to be understood. This analysis reveals a fundamental mismatch between late winter jet stream variability in observations and in GCMs and a potential source of long term predictability of the late winter Atlantic atmospheric circulation.