A good reminder, that; clustering isn't Gospel so we needn't be discouraged, even by a clear group in the Ps trending one way or other, beyond the relatively certain range.

Actually, looking at the 06z GFS Ens, 9 members now have sub -5 850s out to 4th December. I might have got this wrong, but that looks like a day's extension compared to earlier runs? P6 then goes off on a happy one.

Extreme ICON to start the afternoon almost a full blown GH at 144 - ❄️🌲

Ive started my winter model watching on Saturday and I must say I was thinking yesterday evening  we are potentially on the cusp of something here if those LPs can dig SE into Europe and the jet stays to our south.  Encouraging signs from ICON.  Id say its currently (ahead of 12zs) a 40/60 as to whether in a weeks time we are in a cold spell. Certainly no better odds than that.  A damn sight better than staring down the barrel of certain raging zonality, which we may well be in one week if the milder options win out and pattern flattens.

This evening's full suite of operational and ensembles will be interesting to contemplate, and maybe we will be 50/50 or possibly down to a 20/80.  We shall see. 

It will be interesting to see which if any of the other models go for the ICON scenario!

Yes better than the 00z with a stronger Atlantic ridge helping matters 

GFS 12z looks consistent with recent updates. A cold snap looks likely and some places could see sleet or snow. Milder conditions return quite quickly in early December. Not set in stone yet of course. Worth noting this is at odds with the Met O 30 dayer.

The reason is that there are four runs each day and a lot more information available - unless you use the US site mentioned by Darren, which has a huge amount of ECM data.

Yes, the GFS 12z goes on to develop another blister high in the North Atlantic and we get another cold shot.

The pattern shown on the GFS 12 op run to me looks rather reminiscent of what was commonplace during the 2017/18 winter until mid-Feb 2018; a cold blast from the N/NW, then milder for a time, then another cold shot from the north or north-west.

GFS mean now moving to phase 2 of longevity of this cold spell- @168 The alignment of the jet goes SE through the block which is crucial
NB PTB 3 & 4 for example.

I wonder if the mean is sub zero for the 3/4th yet for London !

Still chaos beyond 2nd Dec but before then very good agreement (this is for Aberdeen):

Definitely getting colder and more prolonged,  significant upgrade so far today.

The weekend continues to trend colder and more settled.

Its very possible that Saturday's programmed disturbance across the south will trend further south leaving many cool and dry.

Wintry showers near eastern coasts if the uppers level out at circa -8c.

The strength of the Greenland High and its associated ridging will dictate the longevity of the cold snap.

A toppler followed by an atlantic flow is still favoured by day 10, however, these types of  SE'ward ridging Greeny blocks can be stubborn little fella's to break down once established and I'm not as confident of a warm up this evening compared with yesterday.

ECM going for a GEFS P03

Interesting stuff. Much yet to resolve, but the trends are there.

A thoroughly fascinating weekend of model watching has culminated in a superb early winter run from the ECM and the GEFS also indicate much of interest, not least the control.  Yesterday's charts showed that something was potentially brewing and todays runs have further amplified that potential, a cold snap now seems likely.

Some nice synoptics for a couple of days before the topple ( why 2010 is being banded about I have not a clue) although at t168 range can be liable to change. Phase two of cold snap is certainly wishful thinking at this stage. Snow showers a possibility further north with wintry showers perhaps further south. Still nowt set in stone colder or milder options for next weekend still on the table.