Here is a summary of the NWP output for 12z on Saturday.
Issued 0546z, 13th March 2007.

The models continue to show a change on the way for Sunday and beyond, as a
cold front sweeps in from the NW and introduces much cooler conditions for
all. The colder spell looks like lasting at least 3 days, with northern and
western areas at the greatest risk of seeing rain (or indeed snow on higher
ground). Sheltered areas will be at risk of frost should skies clear for
long at night.

Analysis and evolution to T+120 via GFS
http://85.214.49.20/pics/Rtavn001.png
http://85.214.49.20/pics/avnpanel1.gif
Light winds cover England and Wales, under a ridge, with SW'lies elsewhere.
Tomorrow the ridge builds, with SW'lies for much of the UK. A trough
approaches from the west on Thursday, with further SW'lies. By Friday
another ridge builds from the west, leading to WSW'lies for Scotland and
Northern Ireland with light NW'lies elsewhere.

T+120 synopsis
http://85.214.49.20/pics/Rtavn12015.png /
http://85.214.49.20/pics/Rtavn1201.png
http://85.214.49.20/pics/Rjma1201.gif /
http://85.214.49.20/pics/Rukm1201.gif
http://85.214.49.20/pics/Recm1201.gif /
http://www.meteociel.fr/modeles/nogapse_cartes.php
The jetstream chart shows a strong jet from Newfoundland to Scandinavia,
with the UK south of the jet. At the 500hPa level a weak ridge covers the
UK, with a trough upstream. ECM shows an upper trough over Ireland, with a
ridge building over the western Atlantic. MetO shows a relatively flat
pattern for the UK, with a westerly gradient aloft. NGP, as yesterday, is
greatly different with a marked trough over the North Sea and a strong ridge
northwards from the Azores to the SW of Iceland. GEM has a flat pattern over
the UK in a similar vein to MetO.
At the surface GFS brings WSW'lies for all, with a weak trough to the west.
ECM has strong to gale force WSW'lies as a trough moves over Ireland, while
MetO has slightly lighter westerlies. NGP has cold NW'lies due to a strong
ridge to the west, while GEM is similar to the majority, with WSW'lies and a
trough to the west.

Evolution to T+168
ECM brings a trough across Europe as a ridge builds over the mid Atlantic.
Moderate WNW'lies cover the UK on day 6 and on day 7 the winds become
NNW'lies as the ridge builds to the west.
GFS also shows a ridge building to the west. On day 7 WNW'lies cover the UK
as a trough moves SE'wards, followed by NW'lies on day 7 with the Azores
High to the WSW.

Looking further afield
ECM brings northerlies on days 8 and 9 as the ridge moves closer to the UK.
By day 10 a col covers Northern Ireland and Scotland, with northerlies for
England and Wales.
GFS shows the ridge moving over Scotland and Northern Ireland on day 8,
leading to SW'lies there and northerlies elsewhere. The ridge sinks
southwards on day 9, bringing northerlies to southern England and leaving
the rest of the UK under westerlies. By day 10 the ridge covers the majority
of the UK, with SE England under NE'lies.

Ensemble analysis
(http://expert.weatheronline.co.uk/da...ia/ensdia.html - last
night's 18z)
The ensembles show good agreement of a marked change towards cooler
conditions.