What a classic this is
We have in view a bunch of signals for a bit of added westerly momentum in the short-medium term as the AO increases (and AAM falls a bit, for those in the know), followed by a loss of momentum with amplification returning to most likely save the winter for some of us at least.
- but the models are taking the first part of that to the extremes and the GFS op runs in particular are losing sight of the change in signals thereafter. It seems to happen far too often these days!
Now to be fair, the odds are indeed in favour of a westerly flow for much of the UK up until the final days of Jan at the earliest. There is just the small but not insignificant chance that the westerly momentum is being overdone to the point that a split jet event with a sliding low and an easterly are being overlooked for the latter half of next week (but look at GFSP for an exception to that rule!).
Then comes the window of opportunity, which I have been thinking to be around 28th Jan to 7th Feb, for dramatic changes to occur and set up a colder pattern with snow chances returning. I wish that period could be set in stone but as usual there is the caveat that it could take a week or so longer than that... this theoretical approach to forecasting is still rather experimental after all.
A sudden stratospheric warming or major midwinter warming may be a component in this change of fortunes, but not necessarily. The signs are that events in the tropics will be sufficient to drive the changes we desire with the aid of merely strong, sustained stratospheric warming as opposed to an actual event.
Factor in the usual smaller-scale uncertainties, and the message is that there's still a lot of reason to be hopeful for, but not enough reason to be certain of, some 'proper winter' for much of all of the UK by the middle of February.
That's starting to push it a bit for far-southerners I know, as the sun climbs higher in the sky and exerts greater influence on a larger proportion of the ground surface. The longer it takes, the more impressive the cold air import(s) need(s) to be in order to deliver sustainable lying snow. Feb 2009 does prove that it's very much possible though. Indeed some of my favourite days of weather occurred in that spell, with heavy convective soft hail and snow showers which may have been helped along by the increased solar input 
Behold the cautious optimism 
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T-Max: 30.2°C 9th Sep (...!) | T-Min: -7.1°C 22nd & 23rd Jan | Wettest Day: 25.9mm 2nd Nov | Ice Days: 1 (2nd Dec -1.3°C in freezing fog)
Keep Calm and Forecast On