Here is a summary of the NWP output for noon on Monday.
Issued 0442, 6/12/12

Next week will see a cold spell across the UK. A ridge will cover the
northern half of the UK on Monday, with northerlies elsewhere. During the
working week the winds will veer NE'ly and then ENE'ly, the result of a
Scandinavian High. Low pressure will move westwards towards the UK as the
easterly flow sets in, with an increasing risk of snowfall for eastern areas
in particular, although depending on disturbances in the flow almost
anywhere could see some snow showers. By next weekend the models diverge
somewhat, with ECM maintaining a very cold, blocked outlook and GFS bringing
less cold air in from the east.

Analysis and evolution to T+120 via GFS
A weak ridge covers the UK, leading to NW'lies over England and Wales with
SW'lies elsewhere. Tomorrow a deep low moves over the North Sea, resulting
in a mixture of northerlies and NW'lies. There are further northerlies on
Saturday as a ridge builds to the west, followed by westerlies on Sunday as
the ridge transfers eastwards to France.

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 an omega block centred over Iceland, with the UK
under NW'lies on the right-hand side of the block. The omega block is
present at the 500hPa level too, again centred over Iceland. The supporting
upper lows are located at 52N, 40W and over Germany. ECM shows an upper
ridge to the west and a low to the east, with upper northerlies. GEM is
similar, as is JMA. MetO brings upper NW'lies, with something close to an
omega block centred over Iceland.
At the surface GFS brings cold northerlies and NE'lies as the result of a
high to the NNW and a trough over the North Sea. ECM brings northerlies with
a low to the east, as is mostly the case with GEM - although with GEM a
ridge over the Irish Sea means Northern Ireland lies under SE'lies. JMA
brings a ridge over Scotland, leading to northerlies for England and Wales
and to SW'lies elsewhere. MetO brings light NE'lies as the result of a high
to the east of Iceland.

Evolution to T+168
ECM shows NE'lies setting in as a high over NW Russia ridges strongly
westwards over Scandinavia and the Norwegian Sea. NNE'lies are shown with
GFS on days 6 and 7, as high pressure declines over Iceland and low pressure
moves slowly westwards over the North Sea.

Looking further afield
Days 8 to 10 with ECM show strengthening and increasingly cold long-fetch
ENE'lies as heights fall over the UK and pressure remains high to the NE.
GFS brings ENE'lies on day 8 as a trough moves westwards. There are NE'lies
on day 9, with milder air circulating around a low over France.By day 10 a
trough covers the Scottish borders, leading to easterlies to the north and
WSW'lies to the south.

Ensemble analysis
http://www.meteociel.com/cartes_obs/...&ville=Londres
The ensembles show a generally cold outlook, albeit with a great deal of
scatter from the 16th.

ECM ensembles
http://www.meteogroup.co.uk/meteo/ep...tt6-london.gif
The ECM ensembles also show a generally cold picture, with increasing
scatter after the 15th.