The GEFS ensembles are suggesting that we might be trying to slip into a pattern with a weak negative NAO look to it beyond 240 hours. When looking at extended forecasts of the index, it's important to look at how the forecasts have been doing at the longest time ranges.
Note on the 14 day forecast verification the correlations between the forecast and observed is below .50, that's not a high enough correlation to use the ensemble mean forecast much at that time range. Note how often the