Here is a summary of the NWP output for noon on Saturday.
Issued 0437, 18/10/11

The weekend will see unsettled conditions in the west slowly and erratically
moving eastwards.

Analysis and evolution to T+120 via GFS
Low pressure lies to the NNW, with a trough moving swiftly eastwards over SE
England. Strong westerlies cover the UK and tomorrow they veer WNW'ly. A
weak ridge brings westerlies on Thursday, followed by SW'lies on Friday as
the ridge moves away to the east.

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 weak ridge over the UK with a trough to the
west. At the 500hPa level there are southerlies with a ridge to the east.
The other runs show SSW'lies aloft with a trough to the west.
At the surface GFS has a trough over western areas with SSW'lies elsewhere.
The other models show SSW'lies and southerlies, with lows to the WNW and/or
west.

Evolution to day 7
SSE'lies and SE'lies cover the UK on days 6 and 7 with ECM as low pressure
stalls to the west.
GFS shows southerlies on days 6 and 7 as a trough slowly moves eastwards
over Ireland.

Looking further afield
ECM shows a trough moving northwards on day 8, with easterlies to the north
and SW'lies following behind. There are SSW'lies for all on day 9 as the
trough reaches Scotland, followed by SE'lies ahead of another trough on day
10.
GFS days 8 to 10 were unavailable at the time of issue.

Ensemble analysis
http://www.meteociel.com/cartes_obs/...&ville=Londres
GEFS shows mild and wet weather from the 22nd.

ECM ensembles
http://www.meteogroup.co.uk/meteo/ep...tt6-london.gif
The ECM ensembles show milder conditions from the 23rd.