Here is a summary of the NWP output for noon on Saturday.
Issued 0517, 9th February 2010
Analysis and evolution to T+120 via GFS
NNE'lies cover the UK, with a high to the NW. Tomorrow the winds become northerlies, with low pressure moving towards the UK from the east. Thursday sees pressure build over the Western Isles, with northerlies and NNE'lies for the UK. Some very cold air aloft moves over the far SE. There are further northerlies on Friday, with pressure remaining high over Scotland and Northern Ireland.
T+120 synopsis
http://91.121.93.17/pics/Rtavn12015.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 continues to show a distorted omega, with a weak upper high to the west and a strong zonal jet roaring across the Atlantic and Iberia. The 500hPa level chart shows an upper high to the NW and NE'lies aloft. ECM has NNE'lies aloft, with a ridge to the west. MetO has an upper high to the west and northerlies aloft as a result. Northerlies aloft affect the UK with GEM, too, while JMA has NE'lies and an upper high to the NW.
At the surface, GFS brings NE'lies with a high to the NW. ECM has NNE'lies instead, with its high closer to Scotland and hence with lighter winds there. MetO has a ridge from the west over most of the UK, although moderate NE'lies affect the SE. GEM brings light northerlies with a high to the west, while JMA has a high to the NW and NE'lies.
Evolution to T+168
ECM shows a ridge over all areas except the SE on day 6, with NE'lies there and light winds for most. Day 7 sees a col with light winds for all.
GFS brings northerlies and NW'lies as a ridge sinks southwards on day 6. By day 7 a trough moves southwards, with WSW'lies in advance and cold NE'lies following behind.
Looking further afield
ECM shows low pressure to the west on days 8 to 10. Winds are southerlies initially, but by day 10 a trough covers the UK. To the south milder southerlies are present, with cold easterlies to the north of the trough.
GFS has a deep upper trough becoming established over the UK, with a low over the North Sea. Cold, unstable northerlies and NW'lies cover the UK from days 8 to 10 as a result.
Ensemble analysis
(http://91.121.94.83/modeles/gens/graphe_ens3.php?x=306&ext=1&y=141&run=0&ville=Londres)
The GEFS shows a prolonged cold spell, albeit gradually warming after this weekend.
ECM ensembles
http://www.meteogroup.co.uk/meteo/eps/ensemble-tt6-london.gif
The ECM ensembles show a cold outlook for the next week or so, with the operational being a relatively good match for the mean.
In summary, the end of the weekend will see light winds across northern parts of the UK with widespread frosts. It'll be cloudier further south and east, with snow flurries likely across the SE of England. Monday sees little change but into next week a frontal system associated with a low will move southwards, with a risk of rain and snow as it moves southwards. The models differ greatly regarding the track of the low (ECM to the west of the UK, GFS to the east) so it's impossible to be more specific at this range.