Here is a summary of the NWP output for 12z on Tuesday.
Issued 0555z, 16th March 2007.

The middle of the week will see the cold Arctic air slowly warm over the UK
as the northerly abates. By the weekend an easterly looks likely, as high
pressure builds over Scandinavia and low pressure approaches from the SW. If
it were winter there'd be widespread snow, but it looks like being a few
degrees too warm for most, with snow a possibility over the higher ground in
the north.

Analysis and evolution to T+120 via GFS
http://85.214.49.20/pics/Rtavn001.png
http://85.214.49.20/pics/avnpanel1.gif
A mixture of WSW'lies and WNW'lies covers the UK as a weak ridge moves
eastwards. Tomorrow the winds are westerlies for all, followed by a sharp
transition on Sunday. The day will begin with westerlies for all, followed
by strong NW'lies during the day and through Monday.

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 highly meridonal pattern with a strong jet
passing southwards over the UK. At the 500hPa level there's a ridge to the
west and a low to the east, as is the case with MetO. ECM shows a trough to
the east instead and a stronger ridge to the west. GEM is similar to ECM and
NGP is unavailable today.
At the surface GFS shows a ridge to the west, a trough over the North Sea
and NNW'lies across the UK. MetO is almost the same, with the exception of
stronger winds for eastern areas of the UK. ECM is similar again, with a
shallow trough over eastern Scotland, while GEM has a weak trough over NE
England instead.

Evolution to T+168
ECM shows the ridge collapsing over the UK on day 6, bringing northerlies to
England and Wales with SW'lies elsewhere. By day 7 the ridge to the west
builds NE'watds, allowing NE'lies to affect the UK.
GFS shows a small low to the west forming on day 6, maintaining northerlies
over much of the UK. On day 7 the ridge to the west moves NNE'wards, joining
with a larger high to the NE. Northerlies persist over the UK as a result.

Looking further afield
ECM shows a textbook Scandinavian High for days 8 and 9, with NE'lies across
much of the UK. By day 10 a low approaches from the SW and another low moves
westwards over Denmark, leaving the UK under a mixture of NE'lies,
easterlies and SE'lies.
GFS brings NE'lies for all on day 8 as low pressure fills over Luxembourg.
Day 9 sees a col and light winds for all, followed by SE'lies and SSE'lies
on day 10 as low pressure approaches from the SE.

Ensemble analysis
(http://expert.weatheronline.co.uk/da...ia/ensdia.html - last
night's 18z)
The ensembles persist in showing a colder interlude, at least 3 days but
with a 30% chance of becoming prolonged.