The ability to predict weeks ahead the onset of a period with severe temperature anomalies is closely linked with the ability to forecast accurately the time evolution of the large-scale atmospheric circulation. Therefore, reliable extended-range forecasts of flow patterns such the NAO and Blocking are instrumental for early warnings of severe cold events over Europe (see Ferranti et al. 2018 for further details)
Further reading:
Ferranti L, Magnusson L, Vitart F, Richardson DS. How far in advance can we predict changes in large-scale flow leading to severe cold conditions over Europe?
Q J R Meteorol Soc 2018;144:1788–1802. https://doi.org/10.1002/qj.3341