Here is a summary of the NWP output for noon on New Year's Day.
Issued 0526, 28th Dec 2007

The battleground scenario continues in all runs except the 12z MetO from
yesterday. A large (1050hPa) high will build near Scandinavia and will
almost immediately come under attack from the Atlantic. The attack will
affect all of the UK and at the moment cold rain is the most likely option
for most, around the 3rd. However, a significant minority of the GEFS (and
the operational GFS, GEM) show a very messy situation as a low moves in from
the west and is forced SE'wards by the block, bringing widespread snow. At
the moment it's an outside chance but it'll be worth keeping an eye on the
models over the next couple of runs!

Analysis and evolution to T+120 via GFS
http://85.214.49.20/pics/Rtavn001.png
Strong SSW'lies cover the UK, due to low pressure far to the north. Tomorrow
the winds become SW'lies as a low moves ESE'wards to the NW of Scotland. The
low moves eastwards on Sunday, leaving the UK under NW'lies and westerlies.
New Year's Eve sees a trough move in from the west, with SSW'lies ahead of
it.

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 strong, zonal jet over the North Atlantic with a
split to the immediate west of the UK. The UK itself lies under a ridge. At
the 500hPa level there's a trough over Ireland and southerlies aloft, with a
ridge extending northwards to northern Scandinavia. MetO has a much broader
ridge with SW'lies aloft, while ECM builds a stronger ridge to the NE with
the core of the ridge being over the UK. GEM shows a ridge to the east and
NGP brings a weak ridge over the North Sea with a cut-off high to the north
of Scandinavia.
At the surface GFS brings SSE'lies over the UK due to low pressure to the
west of the UK. MetO has southerlies for all with low pressure further to
the west, while ECM shows SSE'lies and a high to the NE. GEM has a low to
the west and southerlies for all, as is the case with NGP.

Evolution to T+168
ECM shows the high building over NW Russia on day 6, with a ridge over the
UK. Easterlies affect much of England and Wales, with SE'lies elsewhere.
Colder easterlies cover the UK on day 7 as an upper low moves westwards over
the UK.
GFS also builds high pressure over NW Russia on day 6 and low pressure fills
to the SW of the UK. Strong ESE'lies cover the UK as a result, bringing cold
air in from the east. The low moves SE'wards on day 7, bringing cold NE'lies
and snow over much of the UK.

Looking further afield
Day 8 with the ECM sees southerlies as a trouugh approaches from the west
and the high sinks southwards. By day 9 a deep low lies to the north with
strong to gale force SW'lies over the UK. Day 10 sees further SW'lies as
pressure remains low to the north.
Low pressure is forced SE'wards on day 8 with GFS, as pressure remains high
to the NE. The low moves over northern France, bringing snow-laden NE'lies
over the UK with more snow in the west as milder air tries to push in. By
day 9 the milder air wins, with SW'lies moving eastwards across the UK. By
day 10 the whole of the UK lies under milder SW'lies and WSW'lies, with low
pressure to the north.

Ensemble analysis
(http://91.121.94.83/modeles/gens/gra...ille=Lond res)
The ensembles show an unsettled picture for the start of the new year, with
a fifth of the runs bringing a snowy spell for a time.