This is a place for discussion and charts of Christmas Day, with the aim of watching as the models refine their forecasts for the big day. It'll be interesting to see just how far out we get the final picture! I will only be looking at the 0z output, to keep things consistent and manageable.

To kick things off, the GFS now goes out that far. The initial output from the 0z run has a cold cyclonic WNW'ly flow over the UK, low pressure over the North Sea and a secondary low poised to approach from the WSW. There's plenty of sleet and/or snow around in western areas as you'd expect.

https://images.meteociel.fr/im/96/21073/gfs_0_384yum5.png 

Ensemble wise, the 0z GFS offers the following mix:

Control - mild SW'lies with a secondary low to the NW

SW'lies - 9 (5 cyclonic, 4 anticyclonic)

Westerlies, generally with complex low to the north - 7

Trough moving over UK - 4

NW'lies, high to SW - 3

And the other scenarios have 1 each, including a ridge from a Scandinavian High and lows over the North Sea or UK.

The star run today is perturbation 5, which has a cold northerly feed setting in over the UK, with high pressure to the NW and a cold, complex low to the east.

https://images.meteociel.fr/im/22/12395/gens_5_1_384ehg1.png 

On TWO the GEFS stamps are here:

https://www.theweatheroutlook.com/twodata/gefs.aspx?run=na&charthour=384&chartname=ps_2m_maxtemp&chartregion=uk&p=1&charttag=PS%202m%20max%20temp 

It's usually around a week out to be certain, going by the past 20 years, but if it's looking like a very zonal Christmas it can be several days beyond that! Those GEFS stamps are useful, and I'll link to them tomorrow onwards. The reason I use MC, btw, is because it has a handy archive feature, meaning that those reading the thread in a few days should still see the relevant charts.

👍Christmas Day always provides a good focal point to see how the model output firms up as the lead time shortens. 

We had snowfall last Christmas Day in the evening that settled.  First White Christmas for us since 2010.

https://images.meteociel.fr/im/53/12994/gfs_0_360bhx5.png 

The GEFS control has a large high just east of the Azores, with a weak ridge and westerlies over the UK.

The other members cluster around a SW'ly flow, with westerlies and NW'lies from a ridge or high to the west being the next most-likely option.

Anticyclonic SW'lies: 6

Cyclonic SW'lies: 4

Ridge/high to west, NW'lies: 4

Ridge/high to west, westerlies: 4

High to east, southerlies: 3

Complex low to east, cold NW'lies: 2

Other options include a misaligned Scandinavian High, with southerlies, an Icelandic High with cold NNW'lies and widespread snow, or a high centred over the UK.

https://images.meteociel.fr/im/74/3523/gens_16_1_360xao3.png 

Today's standout is perturbation 16, with heavy sleet or snow moving south across much of the UK on Christmas Day. Several other members show sleet or snow in lesser amounts.

It's great to see these snowy, festive, permutations as, despite the vanishingly small chance of them coming off, the fact that they are there shows that all is not yet lost. Imagine a Christmas Day with the sky clouding over and flakes starting to fall as you sit down for Christmas lunch!

I was lucky to be a child in the 80s, lowland snow is getting rarer every year. Even a snow shower is getting a once in a five year event. 

Back on topic this mornings temperatures from the GEFS says it all

https://www.meteociel.fr/cartes_obs/gens_display.php?x=312&y=107&run=6&runpara=0&type=3&ext=1  

The Azores High is displaced northwards on this morning's GFS, lying to the west of the UK. A trough has recently moved southwards over the UK, introducing relatively cold cyclonic northerlies. There's widespread sleet and snow over higher ground in the north and west, with rain over eastern coastal areas.

https://images.meteociel.fr/im/89/6664/gfs_0_336mrn9.png 

The GEFS control has the Azores High ridging over Iberia and a trough crossing the UK. Winds are southerlies in advance and WSW'ly following behind. There's a weak high to the NE of Iceland and trough disruption is ongoing to the NW of the UK.

The ensemble members show the following scenarios:

Anticyclonic SW'lies: 6

Ridge to west with westerlies or NW'lies (not cold): 4

High over British Isles: 4

Trough crossing UK, SW'lies in advance: 3

Ridge from high to east over UK: 3

Cyclonic SW'lies: 2

Complex low over Scandinavia, cold WNW'lies or NW'lies: 2

High over or to immediate west of Biscay, westerlies: 2

The other scenarios include a high to the NE with easterlies over the UK and an Icelandic High with cold NE'lies.

The pattern has changed subtly from yesterday, with a shift away from a straightforward SW'ly pattern - ridging nearby has moved up the charts instead. Cold weather remains unlikely.

The standout today is perturbation 13, which shows that Icelandic High - there is relatively widespread sleet and snow, and milder air only makes slow progress eastwards over the following couple of days.

https://images.meteociel.fr/im/65/9762/gens_13_1_336wpy2.png 

One of those charts which promises much, but delivers mainly rain - still looks good though! And the op isn't unpleasant either, with the Azores High close by and a west or NW'ly flow over the UK... it'd deliver a frost down here at least.

A fairly good chance that some places (and not just exclusively hilly and northern areas) might see some seasonal / wintry weather in the Christmas week.

Alot of flux in the output, no detail consistency to put any more meat on the bones with though

https://www.wetterzentrale.de/en/show_diagrams.php?geoid=50893&model=gfs&var=2&run=6&lid=ENS&bw=1