Here is a summary of the NWP output for noon on Sunday.
Issued 0517, 23rd December 2009.

Next week will start with southerlies and low pressure close by. It's likely
low pressure will cross the UK, bringing rain for most, followed by cooler
NE'lies in its wake. Beyond that there are signs of high pressure building
to the west as the jet roars northwards, bringing a shortlived colder spell.

Analysis and evolution to T+120 via GFS
Low pressure lies to the east of Scotland, leading to westerlies and SW'lies
for most. Tomorrow a col covers the UK, followed by northerlies early on
Christmas Day as low pressure fills over France. Boxing Day sees SW'lies for
all with a low to the north.

T+120 synopsis
http://91.121.93.17/pics/Rtavn12015.png /
http://91.121.93.17/pics/Rtavn1201.png
http://91.121.93.17/pics/Rukm1201.gif
http://91.121.93.17/pics/Recm1201.gif /
http://www.meteociel.fr/modeles/nogapse_cartes.php
The jetstream chart shows a strong jet heading ENE'wards over the Atlantic,
with a secondary jet over the UK also heading ENE'wards. At the 500hPa
level there's a broad westerly flow over the UK, while ECM has upper SW'lies
with a low to the WNW. MetO has upper westerlies as per GFS, as does GEM.
JMA shows upper westerlies too.
At the surface, GFS brings southerlies for England and Wales with a col over
Scotland and Northern Ireland. ECM has SW'lies from a low to the NW, while
MetO places a low east of Scotland with a mixture of westerlies and SW'lies
as a result. GEM has SW'lies and a low over northern Scotland, while JMA has
a low over the North Sea with northerlies for Scotland and WSW'lies
elsewhere.

Evolution to T+168
ECM shows low pressure NW of Scotland on day 6, with southerlies and SW'lies
over the UK. NE'lies affect the UK on day 7 as the low moves SE'wards.
GFS brings a col for most on day 6, albeit with strong and cold westerlies
for northern Scotland. On dya 7 a low deepens over Benelux and strong
NE'lies and northerlies cover the UK.

Looking further afield
ECM shows light northerlies on day 8 as low pressure fills to the SE. Day 9
sees light NNW'lies and northerlies as a ridge moves SE'wards, followed by
WNW'lies on day 10 as the ridge moves away to the SE.
GFS also shows northerlies on day 8, with a low over Biscay and a high to
the west. The high builds on day 9, drawing Atlantic air over the UK from
the NW. By day 10 the high "topples" over the UK, with NW'lies for England
and Wales and SW'lies elsewhere.

Ensemble analysis
(http://91.121.94.83/modeles/gens/gra...ille=Lond res)
The ensembles show increasinly mild weather this coming week, with a high
chance of a short cold spell as pressure builds to the west for the New
Year.