Personally, I'm treating all output for beyond Friday with a pinch of salt at the moment. ECM 12z seems to be backing up GFS wrt a breakdown of sorts from the west next weekend, but I'll only become more convinced of this happening if the models remain consistent with this over the coming few days.
It's worth remembering that up until 2-3 days ago, most model runs were indicating that this plume during the week ahead would only briefly affect the SE of the UK, while areas further to the north and west remained under the influence of the atlantic. The HP to the east now looks as though it will have more of a say in things than appeared to be the case a few days back. I think that sometimes they have a tendency to underestimate the strength of areas of HP while at the same time overcooking lows coming in from the west.
Originally Posted by: David M Porter