I know it's all been said before but you can see why the Met Office doesn't
seriously forecast to the public more than 5 days in advance. I don't know
if it costs any more for the GFS model to be run past 7 days but if it does
it is a waste of money. There can be little value in a model that can
oscillate member runs by 14C (850 hPa values) every six hours other than to
conclude "anything can happen" -because we know that don't we!

Dave