Good morning everyone. Here is my interpretation as I see it from the midnight outputs from GFS, UKMO, GEM, NAVGEM and ECM for today Thursday November 28th 2013.
All models show a large High pressure close to SW Ireland with a light and slack NW flow affecting all areas with low level cloud cover bringing quiet and benign conditions to all areas over the next 24 hours. Through tomorrow cleaner and fresher, colder air will move SE behind a very weak cold front to reach all areas by evening with a dry and bright Saturday away from scattered showers over the North and East for a time, wintry over the hills. By Sunday the NW flow will of weakened as High pressure over the Atlantic ridges back in towards Southern Britain allowing milder and cloudier conditions to gradually topple down across the UK again from the NW through Sunday. This then persists in to the middle of next week with the likelihood of another spell of average temperatures under cloudy skies and light winds for all but the far North where freshening West winds and a little rain develops by then.
GFS then brings a weakening band of rain SE later next week followed by a more coherent spell of rain on a marked cold front which sweeps SE at the weekend bringing very cold and wintry Northerly winds with gales and heavy snow showers to all areas, heavy and prolonged with accumulations in the North and East. On this morning's operational cold weather is then shown to last throughout the following week with snow showers and perhaps some longer spells of snow possible before things quieten down under High pressure at the end of the run but with severe night frosts likely.
UKMO closes it's morning run with next Wednesday being mostly dry and rather cloudy still with a ridge from the Atlantic across the South. The North would see freshening Westerly winds later in the day with the risk of some rainfall later.
GEM this morning shows a cold front slipping SE midweek and bringing a change to colder and dry weather with overnight frost and fog later next week before the High flattens out and milder Westerly winds sink South over Britain followed by another push of colder Polar Maritime air at the end of the run bringing back cold and frosty weather and some wintry showers in the far North and NE.
NAVGEM shows pressure falling from the North later next week as Low pressure moves East to the North. The cloudy and benign conditions over the South would be maintained a while longer before a cold front would swing SE later next week to bring a spell of rain followed by colder weather with wintry showers in the North.
ECM today shows a sharp drop in temperature later next week as Low pressure crosses East to the North and a cold front sweeps SE across all areas. The weather would turn windy and cold with snow showers over all coastal areas, heavy and accumulative over the North and East temporarily before the emphasis shifts to clear skies and widespread penetrative frosts next weekend as High pressure topples in from the West eventually cutting off the Northerly feed.
The GFS Ensembles show only a very short cold snap towards next weekend before things recover to average or even a little above by the end of the run. The operational run is very isolated in it's persistence of cold beyond next weekend with many members showing rising temperatures including the Control run. Rainfall is very low with little for the next week across the South with only short spells of rain shown in Week 2 across the South while closer to average rainfall is likely towards the far North.
The Jet Stream today is projected to stay well to the North and NW of Britain over the next 7 days before it turns SE down across the UK later next week. It isn't long though before it is shown to move back North to a position close to Iceland very late in the run.
In Summary the next week is going to see a lot more of the same with a lot of quiet and benign weather under largely cloudy skies, very light winds and little in the way of rain, sunshine, frost or fog. There will be a temporary transition into a quieter and colder phase for 36-48hrs early in the weekend as a cold front clears SE leaving a short-lived legacy of scattered showers, wintry on hills in the North before the benign, milder and damper air returns on Sunday. It's not until later next week when a more active phase of weather looks like developing as High pressure gives way. A cold front looks like sweeping South delivering what looks like a short but sharp drop in temperatures with snow showers and strong Northerly winds with some likely accumulation of snow over Northern and Eastern high ground. Thereafter there is a strong balance of agreement between the GFS Ensembles and other models that High pressure will move back in across the UK later from the West which in turn will remove the snow shower risk but introduce some very cold nights with severe frost before milder Atlantic winds begin to edge their way back into the UK, first to the NW and on to other areas later.
Martin G
Kilmersdon Radstock Bath Somerset