Here is a summary of the NWP output for 12z on Saturday.
Issued 0516z, 19/12/06

For the forseeable future the outlook is settled and chilly for England and
Wales, with Scotland and Northern Ireland seeing more in the way of cloud
and wind and thus higher temperatures. The high pressure is likely to
dominate until at least Christmas Day, beyond which the models take it
slowly eastwards and thus introduce a milder flow.

Analysis and evolution to T+120 via GFS
http://85.214.49.20/pics/Rtavn001.png
http://85.214.49.20/pics/avnpanel1.gif
High pressure is centred over the UK with light winds for all. Milder air
aloft moves over the UK tomorrow, with the high moving slowly southwards.
Westerlies pick up across Scotland but elsewhere winds remain light. On
Thursday pressure builds over Wales, allowing SW'lies to affect Northern
Ireland and Scotland. Elsewhere winds are still light, as is the case on
Friday as the high builds across England and Wales.

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.jpg /
http://85.214.49.20/pics/Rukm1201.jpg
http://85.214.49.20/pics/Recm1201.jpg /
http://85.214.49.20/pics/Rngp1201.jpg
The jetstream chart shows the UK under a large ridge, with a strong jet
across the North Atlantic, Iceland and Scandinavia. A less powerful jet
heads westwards over France. At the 500hPa level there's a large high
centred over the North Sea with GFS, while MetO centres the high over
England and Wales instead. ECM is similar to MetO, while JMA has the high
over East Anglia instead. The high is over the North Sea with NGP and with
GEM it's to the south.
At the surface GFS brings light winds across much of the UK with a high over
the North Sea and a ridge across England, Wales and Ireland. Northern
Scotland lies under WSW'lies, on the periphery of the high.. MetO shows
WSW'lies and SW'lies for Scotland and Northern Ireland, with high pressure
over England and Wales, while ECM is very similar. JMA brings southerlies
and SSW'lies for Northern Ireland and Scotland respectively, with the high
over the Netherlands. NGP is similar to JMA and GEM has the high further SE,
with WSW'lies across most of the UK as a result.

Evolution to T+168
ECM shows the high declining and moving eastwards. On day 6 winds are light
for England and Wales with SSW'lies and SW'lies elsewhere, followed by
southerlies and SSW'lies across much of the UK on day 7 as the high moves
over the Netherlands.
GFS also shows the high declining. On Christmas Day light winds cover much
of the UK with high pressure over the North Sea. The high moves SE'wards,
leaving England and Wales under light winds on Boxing Day. SW'lies cover
Scotland with southerlies for Northern Ireland.

Looking further afield
Beyond T+168, ECM shows westerlies for day 8 with high pressure over Biscay.
The high moves ENE'wards on day 9, leading to westerlies and a weak ridge
for the UK. By day 10 the high covers France and Germany with WSW'lies for
the UK.
GFS brings SSW'lies over tge UK on day 8 with a large high over much of
Europe. SE England still lies under a ridge, with much of England under the
ridge on day 9 as a low deepens to the west. A trough moves slowly eastwards
towards the UK on day 10, leading to southerlies for all.

Ensemble analysis
(http://expert.weatheronline.co.uk/da...ia/ensdia.html - last
night's 18z)
The ensembles show excellent agreement of a period of mild air aloft,
especially for northern areas of the UK.