Here is a summary of the NWP output for noon on Wednesday.
Issued 0541, 2nd January 2010.

The cold spell shows no signs of abating. Low pressure will bring showers or
longer spells of snow to many eastern areas for the latter half of the week,
with the west likely to see snow also as troughs get carried along in the
flow. Daytime highs will struggle to reach zero in many areas, with even the
coasts only seeing temperatures a couple of degrees above freezing.

Night frosts will be both extensive and moderate to severe, locally very
severe. With the strong winds forecast they're likely to be penetrating too
in many areas. Into the weekend high pressure will approach from the west,
but with the jet on a southerly track it's likely to be torn in two, with
part of the high ending up to our NW. This would mean more settled
conditions in Scotland and Northern Ireland, with a chill NE'ly or NNE'ly
elsewhere.

Analysis and evolution to T+120 via GFS
Low pressure lies to the east of Scotland, bringing NW'lies across the UK.
The low moves swiftly southwards as pressure builds to the NW, leading to
NE'lies tomorrow. Monday sees ENE'lies in the south and light northerlies
elsewhere, with pressure remaining high to the NW. On Tuesday there are
NW'lies and NNW'lies as low pressure moves southwards over Scandinavia.

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 diffluent block to the west, with the
majority of the energy in the southern branch of the jet. As with recent
days, the jet runs over the Azores and into northern Africa. At the 500hPa
level there's a large ridge over the mid-Atlantic with a sharp trough to the
east of the UK. Upper northerlies are the result. ECM has a weaker trough to
the east, still with upper northerlies. MetO shows an upper northerly flow
too, with a trough to the east as per ECM. GEM has a deeper trough and it's
slightly further west, still with upper northerlies. JMA is similar to GEM.
At the surface, GFS has a low over the Netherlands and northerlies across
the UK. ECM has a low to the west of France and a trough over SE England,
resulting in NNE'lies for the UK. MetO shows northerlies for all with a low
to the NE, while GEM has northerlies and a low over northern France. JMA has
a low over the North Sea and northerlies too.

Evolution to T+168
ECM shows NE'lies on day 6 as a ridge crosses Scotland. The ridge builds on
day 7, with westerlies for Scotland and NE'lies elsewhwre.
GFS brings a col on day 6 with light winds. On day 7 pressure builds to the
north, with biting NNE'lies and NE'lies across the UK.

Looking further afield
ECM shows persistent NE'lies from days 8 to 10, with high pressure anchored
to the NW of the UK.
GFS has northerlies on day 8 with the UK sandwiched between a ridge to the
west and a low over the North Sea. The ridge moves NE'wards and builds on
day 9, with NE'lies for the UK (and slightly milder air aloft arriving from
the NE for Scotland). There are easterlies and ENE'lies on day 9 as pressure
falls to the south.

Ensemble analysis
(http://91.121.94.83/modeles/gens/gra...ille=Lond res)
The ensembles continue to show unrelenting cold for at least the next week.