I have been watching early December for sometime now, for a POSSIBLE risk to the start of an early winter. But please note this is in my section WHAT I AM WATCHING and is not a forecast yet.
The reason is high pressure blocking in the Atlantic and high pressure over the North pole. This looks like northerly winds will move over the UK, bringing cold temperatures and risk of snow for the UK.
If we look at the 850 hpa image for 5th December its show the temperature at 5,000 feet. Now look for the -5 c dotted line in the Atlantic and see it drops well South of the UK. This is the magical snow line I look for.
I have to stress this is at the end of the model runs around 370 hours away and thing change.
But I have several other reason why I can see the possibility of a wintery period early to mid December.