Here is a summary of the NWP output for noon on Friday.
Issued 0515, 22nd March 2010

The end of the working week will see rain spreading across the UK as low
pressure moves eastwards across the British Isles. All areas will see rain
and temperatures will fall, widely at or below average. The cooler,
unsettled weather will linger through the weekend.

Analysis and evolution to T+120 via GFS
Southerlies cover the UK, with a low to the west of the UK. Tomorrow the
winds become SW'lies as the low moves northwards. Wednesday sees southerlies
again with a trough over Ireland, followed by SE'lies across the UK on
Thursday from a low to the SW.

T+120 synopsis
http://91.121.93.17/pics/Rtavn12014.png /
http://91.121.93.17/pics/Rtavn1201.png
http://91.121.93.17/pics/Rukm1201.gif
http://91.121.93.17/pics/Recm1201.gif /
http://www.meteociel.fr/modeles/nogapse_cartes.php
The jetstream chart shows a weak and southerly-tracking jet over the eastern
Atlantic, with the UK well to the north. At the 500hPa level there's an
upper low west of Scotland. ECM has an upper low over Scotland, while MetO
has an upper trough over the UK. GEM brings upper southerlies with a low to
the SW, while JMA has easterlies aloft and a low to the SW.
At the surface, GFS brings a slack trough with light SE'lies for Scotland
and WSW'lies elsewhere. ECM has a low over Scotland and a trough over
Northern Ireland, with light winds there. Elsewhere moderate southerlies
affect the UK. MetO has a trough over the UK with light winds for most,
while GEM brings a col for Scotland and southerlies elsewhere. JMA has a low
over the Scottish borders, ith easterlies to the north and stronger SSW'lies
to the south.

Evolution to T+168
ECM brings northerlies on day 6 with a low over eastern areas. On day 7
westerlies cover the UK as the low moves away to the east.
GFS shows strong WSW'lies for most on day 6 as low pressure lies to the NE
and a trough covers Scotland. On day 7 a slack low moves across the UK.

Looking further afield
ECM shows SW'lies followed by westerlies on days 8 and 9, with low pressure
north of Scotland. A col covers the UK on day 10.
GFS brings zonal SW'lies on days 8 to 10, with low pressure to the north and
NW.

Ensemble analysis
(http://91.121.94.83/modeles/gens/gra...ille=Lond res)
The GEFS shows temperatures not far from average from Friday onwards.

ECM ensembles
http://www.meteogroup.co.uk/meteo/ep...tt6-london.gif
The ECM ensembles show cooler conditions for Friday onwards.