Here is a summary of the NWP output for noon on Wednesday.
Issued 0514, 19/01/13

The latter half of the working week will see cold conditions persisting,
with further trough disruption bringing an ongoing risk of rain, sleet or
snow from the west. It's more likely to be snow in northern areas with rain
further south, but as the conditions will be borderline the boundary between
rain and snow is impossible to predict this far out. Into the weekend, the
GEFS and ECM ensembles both show milder air moving northwards, although the
operational ECM maintains the generally cold conditions throughout next
weekend.

Analysis and evolution to T+120 via GFS
ESE'lies and SE'lies cover the UK as the result of lows to the SW and west.
Tomorrow there are ENE'lies with a weak ridge over the UK, followed by
ESE'lies on Monday as a trough moves northwards. Tuesday sees the trough
over the Midlands and northern England, with southerlies to the south and
easterlies to the north.

T+120 synopsis
http://www.wetterzentrale.de/wz/pics/Rtavn12014.png
http://www.wetterzentrale.de/wz/pics/Rtavn1201.png
http://www.wetterzentrale.de/wz/pics/Rukm1201.gif
http://www.wetterzentrale.de/wz/pics/Recm1201.gif
http://www.wetterzentrale.de/wz/pics/Rjma1201.gif
The jetstream chart shows a strong and relatively zonal jet over the North
Atlantic. At the 500hPa level there's a col, while MetO has a weak upper low
over the North Sea. ECM has an upper low to the west with weak southerlies
aloft, while GEM has a col. JMA shows upper southerlies as with ECM.
At the surface GFS brings a col. MetO has a low over northern France with a
trough extending over SE England and the Midlands. Winds are easterlies to
the north of the trough and westerlies to the south and west. ECM has a col
over England with southerlies elsewhere from a trough to the west. GEM shows
ENE'lies with a low over Biscay, while JMA has a trough moving across the UK
with a mixture of southerlies and SE'lies.

Evolution to T+168
ECM shows a col on day 6 and on day 7 a trough moves eastwards, bringing
southerlies and SSE'lies. GFS has southerlies moving eastwards on day 6,
followed by westerlies on day 7 from a low over the North Sea.

Looking further afield
Days 8 to 10 with ECM bring southerlies followed by a col as a trough
disrupts over the UK. On day 10 there's a deep low to the south, with
easterlies over the UK. GFS shows southerlies on day 8 followed by light
winds for most as a trough moves eastwards on days 9 and 10.

Ensemble analysis
http://www.meteociel.com/cartes_obs/...&ville=Londres
The GEFS shows cold or very cold conditions for the next week, followed by a
return to nearer-normal conditions.

ECM ensembles
http://www.weathercast.co.uk/service...-forecast.html
ECM also shows cold or very cold conditions for a week, with milder
conditions thereafter.