Here is a summary of the NWP output for noon on Thursday.
Issued 0447z, 8/05/11

The end of the week will see low pressure to the north with showers in the
north and west. Further south it's likely to be mostly dry. During the
weekend a weak ridge is likely to bring settled conditions for much of the
UK before rain spreads eastwards on Monday.

Analysis and evolution to T+120 via GFS
The UK lies under SE'lies from a deep low to the WSW. Tomorrow the winds
become southerlies as the low fills to the west. Lighter southerlies affect
the UK on Tuesday, followed by SW'lies as a trough approaches from the west
on Wednesday.

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 SW'lies over the UK, with a trough to the NW.At
the 500hPa level there's also a SW'ly flow, The other runs show a shallower
upper trough with WSW'lies instead.
At the surface the runs all show WSW'lies with a low to the north. GFS has a
shallow trough over the far SE while ECM has a weak ridge over the south
instead.

Evolution to T+168
ECM shows WSW'lies on day 6 as a trough crosses Scotland. On day 7 a weak
ridge brings WNW'lies.
GFS brings westerlies on day 6 with a low to the NE. On day 7 a weak ridge
brings WNW'lies and NW'lies.

Looking further afield
Days 8 to 10 with ECM show westerlies strengthening and backing to become
WSW'lies by day 10. A deep low lies to the ENE of Scotland by day 10.
GFS brings strong SW'lies on day 8 due to a deep low to the NW. The low
fills and moves NE'wards by day 10, allowing lighter WSW'lies to affect the
UK.

Ensemble analysis
http://www.meteociel.com/cartes_obs/...&ville=Londres
The GEFS shows temperatures not far from average over the coming week, with
generally dry conditions from the 11th to the 13th.

ECM ensembles
http://www.meteogroup.co.uk/meteo/ep...tt6-london.gif
ECM also shows near-normal temperatures.