Here is a summary of the NWP output for noon on Wednesday.
Issued 0558, 27th March 2010

The latter half of the working week will see generally cool, if not cold,
weather and plenty of rain due to nearby low pressure. Over high ground (and
to lower levels in a few places on Wednesday) the precipitation will be
wintry. By Friday temperatures rise slowly but the weather looks like
remaining unsettled for a while yet.

Analysis and evolution to T+120 via GFS
Low pressure lies to the north, with a secondary low over Wales. A mixture
of westerlies and SW'lies covers the UK as a result. SW'lies affec the UK
tomorrow as low pressure remains to the north. On Monday there's a brief col
before a low crosses England into Tuesday, with cold northerlies as it moves
eastwards.

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 trough over the UK, with a weak jet upstream. At
the 500hPa level there's an upper low to the NW with a trough over the North
Sea and NW'lies aloft for the UK. ECM has a low to the north and westerlies
aloft, as is the case with MetO. GEM has a low to the WNW and NW'lies aloft
while JMA brings an upper trough over the UK.
At the surface, GFS brings strong to gale force NW'lies with a deep low off
southern Norway. ECM has a less-deep low closer to Scotland, with westerlies
and WNW'lies for the UK. MetO brings a WSW'ly flow with a trough over
Ireland, while GEM shows NW'lies due to a low over the North Sea. JMA has a
low over East Anglia with northerlies for most of the UK.

Evolution to T+168
ECM brings WSW'lies on day 6 with a low to the north. On day 7 a secondary
low approaches from the west, leading to southerlies.
GFS shows a weak ridge and westerlies on day 6. On day 7 there are SW'lies
as a trough moves in from the west.

Looking further afield
ECM shows a trough crossing the UK on day 8, with southerlies ahead of yet
another low on day 9. The low crosses Ireland on day 10.
GFS brings a mixture of WNW'lies and NW'lies on days 8 to 10 with high
pressure to the west.

Ensemble analysis
(http://91.121.94.83/modeles/gens/gra...ille=Lond res)
The GEFS continues to show a cold spell next week.

ECM ensembles
http://www.meteogroup.co.uk/meteo/ep...tt6-london.gif
The ECM ensembles show a couple of cold days next week.