Here is a summary of the NWP output for noon on Tuesday.
Issued 0546z, 22/04/11

A change is still on the way, with temperatures falling markedly midweek and
with an increasing risk of rain as pressure falls to the SW.

Analysis and evolution to T+120 via GFS
SE'lies and ESE'lies cover the UK, with a high to the NE. A col moves over
the UK tomorrow and lingers through Sunday and Monday.

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 the same as it has done for weeks - the jet is far
to the NW, with a ridge over the UK. At the 500hPa level there are SW'lies,
as is the case with JMA. MetO and ECM have upper NW'lies instead, with a
ridge to the SSW.
At the surface the runs all show NE'lies with high pressure to the north.

Evolution to T+168
ECM has ENE'lies and NE'lies on days 6 and 7 as high pressure dominates
Scandinavia.
GFS has a ridge over Scotland on days 6 and 7, with NE'lies for England and
Wales and SE'lies elsewhere.

Looking further afield
ECM shows a col on day 8, followed by SE'lies as low pressure moves NE'wards
over SW England.
Moderate easterlies and ENE'lies cover the UK on days 8 to 10 with GFS as
pressure falls to the south.

Ensemble analysis
http://www.meteociel.com/cartes_obs/...&ville=Londres
The GEFS shows an increasingly cool and wet picture.

ECM ensembles
http://www.meteogroup.co.uk/meteo/ep...tt6-london.gif
ECM also shows marked cooling after the 25th.