I'm off to the Alps in a week and as such have been examining the GFS
Ensembles. I've noticed that the ensembles have been quite consistent
with high pressure expected to build to the north/west [of the Alps]
allowing cooler/colder conditions to prevail.

Yet the actual operational run seems to be quite keen to maintain the
high over Spain with, no ridge to the north, [and bring freezing
levels up to nearly 3000m, not good for skiing] On a number of
occasions is has been a clear outlier.

Is there any explanation for this? Does the operational run, over
time, hold greater weight over the other perturbations? Should I be
nervous about getting ‘milded out’