Here is a summary of the NWP output for noon on Saturday.
Issued 0534, 29th Jan 2008

The cold snap is still on the way, with Saturday being a cold day across the
UK. There's considerable uncertainty about disturbances caught up in the
flow, but snow could be quite widespread especially in northern and western
areas. Sunday looks like a transition back to milder weather as a weak ridge
builds from the SW ahead of the next low. However, there's a 20% chance
according to the GEFS that the low to the west will disrupt, keeping the UK
in colder air with further snow. The European models don't seem very keen at
all on that idea, though, so a return to milder weather for the start of
next week is by far the most likely option at this stage.

Analysis and evolution to T+120 via GFS
http://85.214.49.20/pics/Rtavn001.png
A trough is moving in from the west, with SW'lies and SSW'lies over the UK.
Tomorrow the trough lies to the east, with NW'lies for all. Thursday sees a
deep low to the north and strong to gale force SW'lies over the UK, followed
by much colder NW'lies and WNW'lies on Friday as a trough moves southwards.

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/Rukm1201.gif
http://85.214.49.20/pics/Recm1201.gif /
http://www.meteociel.fr/modeles/nogapse_cartes.php
The jetstream chart shows a split jet to the west of Greenland, with most of
the energy going to the southern branch. There's a jet streak over the North
Sea, with a ridge over the UK at the 500hPa level. ECM also has a ridge near
to the UK on its 500hPa chart, with a trough to the east. GEM shows a trough
over the UK and the North Sea, while NGP has a trough to the west and a
ridge to the east, with upper SSW'lies.
At the surface GFS brings SSW'lies for all, with a trough to the west. ECM
has westerlies and a weak ridge over Ireland, while GEM shows much colder
westerlies with low pressure to the north and a secondary low over
Luxembourg. NGP brings strong to gale force southerlies over the UK, due to
complex low pressure to the WNW.

Evolution to T+168
ECM shows southerlies for all on day 6, with a large low to the WNW. On day
7 the low becomes complex, with one centre to the NW. SSW'lies cover the UK
as a result.
A trough approaches from the west on day 6 with GFS, leading to SE'lies
across much of the UK. By day 7 low pressure becomes complex over the UK,
with a centre over southern Scotland and another centre over the English
Channel.

Looking further afield
WSW'lies cover the UK on day 8 with ECM, due to a trough to the north and a
shallow secondary depression moves eastwards over the UK. On day 9 a weak
ridge brings westerlies for all, followed by SW'lies on day 10 with a low to
the NW.
GFS shows westerlies for all on day 8 due to a weak ridge, followed by
SW'lies on day 9 with a deep low to the NW.Day 10 sees little change, with
further SW'lies.

Ensemble analysis
(http://91.121.94.83/modeles/gens/gra...ille=Lond res)
The ensembles continue to show three cold days followed by a return to much
milder conditions.