so like 18z GFS, I think its time to take a deeper look at the 06z GFS, particularly at 96hrs:
Introduction:
Each low will effectively perform so kind of fuijiwara effect around each other and will probably eventually become one gyre somewhere close to the south of England. The key location of where that sets up is totally dependent on the constituent lows and where they end up.
GFS 06z:
The GFS has three lows that all interact with each other to beocme one larger gyre which rotates around each other.
1: Limpet low is further north than all other models and more stretched out with a elongated upper trough. This feature starts to get absorbed into the gyre further west pretty quickly and blocks off any cold air from getting further south and keeps the cold air locked away to the north whilst a fair part of the country remains under the low.
2: Iberian low is modelled more realistically this time round but because on No.1, it doesn't really matter.
3: The Atlantic low is actually a little weaker than the likes of ICON 06z, but because of the location of no.1 it manages to absorb and no.3 become the dominant airflow.
The whole lot once connected like they are at 120hrs will pivot around a central point which will increasingly be located close to the low pressure in the Atlantic. This will bring some cold air further south but probably not enough.
00z ECM:
1: Limpet low further south which keeps it away from the atlantic low for much longer.
2: Iberian low rotates up as per GFS but absorbs the Limpet low this time which pushes cold air in from the east.
3: Atlantic low remains disconnected from the UK low this time so ends up further south-east than the GFS has there isn't that tug from the north as No.1 doesn't end up getting dragged westwards.
ECM synoptically is very different with how it handles no.1, which ends up far enough south to start with that it ends up getting absorbed by No.2 instead of no.3 low which allows the cold air to come in from the east. Eventually No.3 DOES absorb it all and become the central gyre but its far enough south to be no issue.
Conclusion:
The limpet low remains utterly key to the evolution. The GFS has actually shifted overnight from the 18z in that the last set of runs the GFS had the low pressure being way further SW which helped to blow up the Iberian low. This time round it gets stuck over Scotland instead instead and rotates so far NW that it gets absorbed into the flow.
So the GFS is NOT being consistent run to run despite the way it might appear on the surface, as its getting to the same conclusion with a variety of means depending on exactly what it does with the limpet low. The ECM and indeed all other models keep the UK low far enough SE that we don't make the connection between No.1 and No.3 which keeps the polar boundary moving further south rather than getting stuck over N.England.
So what do I think is going to happen?
I think its really going to depend alot on exactly where the core of the low pressure No.1 ends up. Basically wherever it ends up sitting then add another 100-150 miles south for a sagging of the whole complex and that will be pretty much your snow line for 120-144hrs.
The good news is the GFS is really on its own, and ironically is now handling the low no.1 *exactly* the same way the ECM did a couple of days ago, so the GFS has backtracked whilst the ECM has shifted towards the OG GFS idea, work that one out!
ICON 06z has made a move towards the GFS solution with regards to no.3, and that is somewhat worrying because a stronger No.3 means we have much less leeway with how no.1/2 evolve. The stronger no.3 means its reach is larger and the odds of absorption higher, so we need no.1/2 to effectively make up the difference with a good evolution. Luckily the ICON 06z does appear to behave with those lows, but its a sign that the GFS solution is a possible one, even if I think its perhaps not the more likely one.
EDIT - The GFS ensembles are not going to be worth a dime in this set-up, and probably same for the ECM ensembles. The set-up is so subtle that they will both likely follow their operational as this is likely down to how they are handling the LP within their separate algorithms/data inputs.
They will all flip at the same time at some point, either towards the GFS or the GFS towards the ECM, but it will probably happen pretty much in one hit through the ensembles and operationals. https://www.netweather.tv/forum/topic/95065-model-output-discussion-is-the-beast-awakening/?do=findComment&comment=4412334