Here is a summary of the NWP output for noon on Boxing Day.
Issued 0536, 22nd December 2007

The latter half of next week is likely to be a typical "zonal" week, with
troughs moving eastwards bringing rain to most (and possibly snow over the
highest ground in Scotland). Between the troughs there will be sunshine and
showers, with temperatures generally average or a couple of degrees above.

Analysis and evolution to T+120 via GFS
http://85.214.49.20/pics/Rtavn001.png
Southerlies and SE'lies cover the UK, with high pressure to the ESE and a
trough to the west. Tomorrow a ridge builds across England and Wales, with
westerlies and WSW'lies elsewhere. Another trough approaches from the west
on Christmas Eve, bringing southerlies to all. The trough moves slowly
eastwards on Christmas Day, with southerlies in advance and NW'lies
following behind.

T+120 synopsis
http://85.214.49.20/pics/Rtavn12015.png /
http://85.214.49.20/pics/Rtavn1201.png
http://85.214.49.20/pics/Rjma1201.gif /
http://85.214.49.20/pics/Rukm1201.gif
http://85.214.49.20/pics/Recm1201.gif /
http://www.meteociel.fr/modeles/nogapse_cartes.php
The jetstream chart shows a shortwave pattern across the North Atlantic,
with a ridge over the UK. At the 500hPa level there's a weak ridge over the
UK, with upper WSW'lies. On the MetO run there are upper SW'lies with a
strong zonal flow over the Atlantic. ECM has upper WSW'lies, while GEM
brings upper westerlies and a weak ridge.
At the surface GFS brings SW'lies with low pressure to the north. The winds
become westerlies on day 7 as a trough moves swiftly eastwards.

Evolution to T+168
ECM shows SW'lies on day 6 as a trough approaches from the west. Day 7 sees
WSW'lies as the trough moves away to the east.
GFS brings a SW'ly flow over the UK on day 6 due to a trough to the west.
The winds become westerlies on day 7 as the trough moves eastwards.

Looking further afield
Day 8 with the ECM sees SW'lies due to a trough to the west. The trough
moves away eastwards on day 9, with westerlies following behind. On day 10
the winds become WNW'lies as pressure builds to the west.
SW'lies cover the UK on day 8 with GFS, due to a high to the south. The high
builds and moves eastwards on day 9, bringing mild southerlies for all. Day
10 sees little change as the high builds in situ.

Ensemble analysis
(http://91.121.94.83/modeles/gens/gra...ille=Lond res)
The ensembles show a typical "sine wave" mobile pattern over the next week,
but beyond that there's much less certainty, with the operational GFS being
one of the mildest runs for a time. A good 33% of the runs show a prolonged
cold spell at the start of January.