More Snow Before Xmas For Some?

[Nick F]

It has been another bitterly cold night across the UK, the snowfields over parts of England have seen some rather low temperatures such as -17.0C at RAF Benson in Oxfordshire, -14.6C in Woodford near Greater Manchester both at 5am – Woodford still -12.2C at 10am.

The deep pool of cold air which sunk south last Thursday across the UK has lingered over the weekend and now forms a wedge of deep cold air stretching from Ireland across the UK and NE up towards the Baltic Sea. On the southern side of this wedge of cold air is a W to E jet stream and parallel thermal boundary just to the south of it running across Nern France, Germany and Poland, to the south of the boundary is less cold Atlantic air spilling across SW Europe. The jet and thermal boundary has been and will be a breeding for lows to develop to the SW and moving W to E close to southern UK and over the near continent. One low developed in the SW and moved east up the M4 corridor on Saturday bringing a lot of snow across the southern half of England – particularly the S Midlands and northern Home Counties. Then yesterday, a deep low developed further south and tracked ENE across northern France and the Low Countries, dumping a lot of snow along with high winds (gusts of 60mph on the near continent) causing major travel disruption over the Channel. Today, yet another area of low pressure forming near the jet SW of Ireland yesterday afternoon, is now centred over Cornwall (see current analysis charts below),

http://meteocentre.com/analyse/map.php?hour=0〈=en&map=UK

… the occluded front wrapping around the low is now pushing N across the Bristol Channel into south Wales and E towards central southern England. The band mainly of snow inland has already brought 10cm widely across parts of Cornwall and Devon, with local reports of up to 20cm around Exeter and up to Somerset, the current radar shows some heavy radar returns now across Dorset. The band of snow will then stretch eastwards from S Wales across southern England through the day, 06z GFS shows the band of snow reaching London and the Home Counties between 3 and 6pm, the heaviest snow generally staying south of the M4 and Thames through Greater London. 06z NAE differs by taking heavy snow N into S Wales and SW Midlands with only light snow moving east across southern counties – given wild swings between runs with NAE – don’t buy its precip predicts – especially as 00z UKMO (Global) and ECM are similar to GFS. So expect 10-15cm quite widely across SW England and S Wales with 20cm locally – further east 5-10cm over southern England with up to 15cm over high ground.

Further north, a slow-moving area of low pressure over the North Sea continues sit close to Eastern Scotland – continuing to feed snow showers across here for the rest of today and again tomorrow, bringing further accumulations.

For Tuesday, snow looks like it will die out across the SE in the morning, GFS suggests outbreaks of snow continuing across Wales and SW England – presumably part of stronger bit of forcing beneath cold pool showing on 500mb charts across the Celtic/Irish Sea - despite the general weakening of the occlusion overnight into Tuesday across the south – NAE and UKMO produce area of rain, sleet and snow further west mainly over west Wales and over Celtic Sea. Otherwise, Tuesday mainly dry and very cold, though still snow showers across eastern Scotland.

Wednesday, the uncertainty grows again, a deep Atlantic trough arrives to the west, which will tend to align the jet more SW to NE on its forward side – which will generate an area of low pressure over Iberia and France, ECM shows a shortwave develop over Nern France as an extension of this, this shortwave then develops as a low over the south North Sea by early Thursday – with snow developing in its circulation on the western flank across the Midlands, E Wales, eastern and northern England Wednesday PM. GFS and UKMO don’t develop this low – rather have a NE’erly flow with low pressure on near continent but has snowfall across parts of Wales, Midlands, southern and eastern England. Given ECM id different, would side with GFS and UKMO.

The rest of the week, still threat of snow perhaps in the east early Thursday, but then on threat of snow looks to diminish as high pressure builds in from the west. So Xmas day looks be dry and cold. Increasing signs that it will turn milder next week from the SW as low pressure becomes dominant to the NW and pressure builds in across SW Europe.

[Stu_London]

Thanks Nick

That's a good read.

As far as todays band goes, I think it is remaining in fairly robust shape so far and is moving due NE on the latest radar.

No reason why this can't reach London in fairly reasonable shape and could cause some problems from around 3pm

[A.J]

Thanks Nick, a very articulate, and informative forecast!

[R.P. McMurphy]

Great forecast Nick. It's actually good to see this instead of the usual IMBY posts on the Model Thread at the moment lol.

+1 for you Nick, brilliant

[mandi35]

that is a good read if you live further south im in the north west region and still have 10inches of snow im totally snowed in blue sky sun out big icicles everywhere nick are we going to see anymore heavy snow for north west ie skelmersdale in lancashire

[Mr Sleet]

Good job Nick, well put together.

[Stamford Bobby]

Yes excellent forecast Nick, just what most of us "lurkers" and eager learners are looking for. Will be interesting to see if todays precip makes it to my area before running out of steam. Enjoying reading the forum through this spell, especially the the opinions of all the regulars.

Fingers crossed for Peterborough midweek so TEITS can get his snow at last!

[Stuart]

Great Forecast nick

[johnholmes]

thanks Nick-superbly explained from the models

folks do read it for an umbiased view of the likely developments into Christmas.

[Nick F]

that is a good read if you live further south im in the north west region and still have 10inches of snow im totally snowed in blue sky sun out big icicles everywhere nick are we going to see anymore heavy snow for north west ie skelmersdale in lancashire

Only one model this morning - ECM showing much in the way of snow for NW England this week, particularly Wednesday PM. GFS, UKMO suggesting it'll be mostly dry, but IMO there could be some light snow pushing up from the south perhaps over next few days.

Temperatures are well below freezing still over much of the UK, at 12 noon -8.1C at Pershore and -8.5C at Shawbury (both in the W Midlands); -8.8C at Woodford near Manchester. An onshore flow along the south coast from Cornwall to Kent is bringing less cold air off the Channel with +3-4C being recorded here, but not far inland it's below freezing so we should only see rain or sleet near the coast as the band of precip spreads east along southern counties.

[Mr Freeze]

superb read. Thank you.

[Nick F]

Monday evening update

The movement east of snowfall across southern counties has been fairly well modelled, but another separate area of snow which has moved slowly north across S and E Wales and the Midlands (including Birmingham area) this afternoon and evening - has been less well modelled until the 06z and 12z runs picked it up – though 00z NAE seemed to indicate this happening this morning. A few more hours of light to moderate snow across Kent, Sussex, Surrey and S London tonight bringing perhaps 5-10cm in places maybe up to 10-15cm over North Downs, before dying out in the early hours. The snow across the Midlands and Welsh Borders easing and becoming light and patchy overnight too, though 12z GFS, UKMO and NAE showing snowfall picking up across north and west Wales and over the Irish Sea during the morning - with snowfall perhaps affecting west Wales/Irish Sea through the day due to presence of a cold pool/upper low aloft as shown by the blob of colder air by blues on the 500mb height and temperature charts below:

Otherwise, Tuesday looks to be a much less snowier day for the bulk of the UK, though perhaps a few snow showers still possible across eastern Scotland, but perhaps not as frequent as recent days.

On Wednesday, the upper cold pool/low over the Irish Sea looks to drift east across Wales and England, so the likely sleet and snow across west Wales and Irish Sea tomorrow will drift east tomorrow night across Wales and parts of SW England and Midlands. Then spreading east across other parts of England. Still sketchy the northern limit, as recent days, 12z GFS has bulk of snow across Midlands and southern half of northern England with areas south of M4 dry – while NAE and UKMO keeps across southern parts of England as far north as south Midlands across to Suffolk. UKMO faxes this evening for 00z and 12z Weds shows a trough marking the eastward moving cold pool on Wednesday:

This area of snow, wherever it spreads east across, could again bring 5-10cm in places bringing further accumulations and continuing the disruption to travel over areas already badly hit over last few days.

However, Wednesday could see the last of the heavy snowfalls this week for England and Wales at least, with a ridge high pressure building in from the west on Thursday which will see a mainly dry and cold end to the week with hard or severe frosts and perhaps freezing fog forming as winds fall light. There is indications that snow showers could to return to Scotland on Thursday and Friday as low pressure flirts with the far north.

And what will the weather likely be for Xmas day? Well the t+120 charts from GFS, ECM and UKNO this evening for 12z Saturday all suggest a ridge of high pressure across the uk, so most likely it will be dry, cold and frosty – sunny too where any freezing fog doesn’t linger. However, models seem also to agree on a breakdown on Boxing Day, as Atlantic low pressure nudges in to the NW with a frontal system pushing rain preceded by snow across the UK during the day followed by less cold air and a thaw into next week. All a long way off – but increasing support finally on a break down by the end of the Xmas weekend.

[johnholmes]

Monday evening update

thanks again Nick

[keithlucky]

Monday evening update

The movement east of snowfall across southern counties has been fairly well modelled, but another separate area of snow which has moved slowly north across S and E Wales and the Midlands (including Birmingham area) this afternoon and evening - has been less well modelled until the 06z and 12z runs picked it up – though 00z NAE seemed to indicate this happening this morning. A few more hours of light to moderate snow across Kent, Sussex, Surrey and S London tonight bringing perhaps 5-10cm in places maybe up to 10-15cm over North Downs, before dying out in the early hours. The snow across the Midlands and Welsh Borders easing and becoming light and patchy overnight too, though 12z GFS, UKMO and NAE showing snowfall picking up across north and west Wales and over the Irish Sea during the morning - with snowfall perhaps affecting west Wales/Irish Sea through the day due to presence of a cold pool/upper low aloft as shown by the blob of colder air by blues on the 500mb height and temperature charts below:

Otherwise, Tuesday looks to be a much less snowier day for the bulk of the UK, though perhaps a few snow showers still possible across eastern Scotland, but perhaps not as frequent as recent days.

On Wednesday, the upper cold pool/low over the Irish Sea looks to drift east across Wales and England, so the likely sleet and snow across west Wales and Irish Sea tomorrow will drift east tomorrow night across Wales and parts of SW England and Midlands. Then spreading east across other parts of England. Still sketchy the northern limit, as recent days, 12z GFS has bulk of snow across Midlands and southern half of northern England with areas south of M4 dry – while NAE and UKMO keeps across southern parts of England as far north as south Midlands across to Suffolk. Prefer the UKMO and NAE solution for now given the better handling lately. UKMO faxes this evening for 00z and 12z Weds shows a trough marking the eastward moving cold pool on Wednesday:

This area of snow, wherever it spreads east across, could again bring 5-10cm in places bringing further accumulations and continuing the disruption to travel over areas already badly hit over last few days.

However, Wednesday could see the last of the heavy snowfalls this week for England and Wales at least, with a ridge high pressure building in from the west on Thursday which will see a mainly dry and cold end to the week with hard or severe frosts and perhaps freezing fog forming as winds fall light. There is indications that snow showers could to return to Scotland on Thursday and Friday as low pressure flirts with the far north.

And what will the weather likely be for Xmas day? Well the t+120 charts from GFS, ECM and UKNO this evening for 12z Saturday all suggest a ridge of high pressure across the uk, so most likely it will be dry, cold and frosty – sunny too where any freezing fog doesn’t linger. However, models seem also to agree on a breakdown on Boxing Day, as Atlantic low pressure nudges in to the NW with a frontal system pushing rain preceded by snow across the UK during the day followed by less cold air and a thaw into next week. All a long way off – but increasing support finally on a break down by the end of the Xmas weekend.

[Fozfoster]

Cheers. ff

[pinball wizard]

Monday evening update

The movement east of snowfall across southern counties has been fairly well modelled, but another separate area of snow which has moved slowly north across S and E Wales and the Midlands (including Birmingham area) this afternoon and evening - has been less well modelled until the 06z and 12z runs picked it up – though 00z NAE seemed to indicate this happening this morning. A few more hours of light to moderate snow across Kent, Sussex, Surrey and S London tonight bringing perhaps 5-10cm in places maybe up to 10-15cm over North Downs, before dying out in the early hours. The snow across the Midlands and Welsh Borders easing and becoming light and patchy overnight too, though 12z GFS, UKMO and NAE showing snowfall picking up across north and west Wales and over the Irish Sea during the morning - with snowfall perhaps affecting west Wales/Irish Sea through the day due to presence of a cold pool/upper low aloft as shown by the blob of colder air by blues on the 500mb height and temperature charts below:

Otherwise, Tuesday looks to be a much less snowier day for the bulk of the UK, though perhaps a few snow showers still possible across eastern Scotland, but perhaps not as frequent as recent days.

On Wednesday, the upper cold pool/low over the Irish Sea looks to drift east across Wales and England, so the likely sleet and snow across west Wales and Irish Sea tomorrow will drift east tomorrow night across Wales and parts of SW England and Midlands. Then spreading east across other parts of England. Still sketchy the northern limit, as recent days, 12z GFS has bulk of snow across Midlands and southern half of northern England with areas south of M4 dry – while NAE and UKMO keeps across southern parts of England as far north as south Midlands across to Suffolk. Prefer the UKMO and NAE solution for now given the better handling lately. UKMO faxes this evening for 00z and 12z Weds shows a trough marking the eastward moving cold pool on Wednesday:

This area of snow, wherever it spreads east across, could again bring 5-10cm in places bringing further accumulations and continuing the disruption to travel over areas already badly hit over last few days.

However, Wednesday could see the last of the heavy snowfalls this week for England and Wales at least, with a ridge high pressure building in from the west on Thursday which will see a mainly dry and cold end to the week with hard or severe frosts and perhaps freezing fog forming as winds fall light. There is indications that snow showers could to return to Scotland on Thursday and Friday as low pressure flirts with the far north.

And what will the weather likely be for Xmas day? Well the t+120 charts from GFS, ECM and UKNO this evening for 12z Saturday all suggest a ridge of high pressure across the uk, so most likely it will be dry, cold and frosty – sunny too where any freezing fog doesn’t linger. However, models seem also to agree on a breakdown on Boxing Day, as Atlantic low pressure nudges in to the NW with a frontal system pushing rain preceded by snow across the UK during the day followed by less cold air and a thaw into next week. All a long way off – but increasing support finally on a break down by the end of the Xmas weekend.

Thanks for that Nick, its a really informative and readable analysis. Its interesting you mention a line to Suffolk, looking at that T48 Fax the dam line is across EA and the front bringing PPN is a warm one, do you envisage significant marginality along coastlines, and if so where do you envisage the snow/rain boundary being?

[ZONE 51]

Thanks Nick. enjoyed the read, i like the idea of a sunny christmas day, not seen a blue sky for ages! Be good with passing snow showers to..

[Nick F]

Tuesday Noon Update

Another very cold night across parts of northern UK, though southern half the UK was a little less cold than recent nights what with all the cloud and patchy snow around, though still a couple of degrees C below at dawn. Readings for 6am this morning: in the NE of England, Resedale Camp reached -14.9C, Topcliffe and Leeming just over -13C; and another very cold night for Northern Ireland after a record low of -18C the night before – Belfast reaching -12.5C at 6am.

This morning, mainly light snow has continued to fall across northern half of Wales, west Midlands, and Cheshire near the western extent of the occlusion lying from the Irish Sea – North Wales – N Midlands – Norfolk. Heavier pulses of snow are evident on the radar across the Irish Sea beneath a upper cold pool/low shown on the 500mb chart below, this creating the lift generally across Wales, NW England into Midlands for snow that is likely to become more extensive, if mainly light through this afternoon.

Elsewhere, extensive cloud, mist and fog patches across much of the England and Wales, though some breaks evident across northern England and Scotland. Temperatures are rising above freezing across southern counties south of the M4 with 1-2C here. North of the M4, below freezing with temperatures still currently as low as -7 to -9C across northern England and Scotland.

- 12z UK Analysis

Tonight and through Wednesday, models finally agreeing on snow to become more extensive across north Wales, The Midlands, southern half of northern England and later eastern England, as the upper low/cold pool moves east. Some heavier bursts possible – so further disruption likely for central and eastern UK tonight and tomorrow. Snow looks to ease from the west and clearing the east tomorrow evening and night.

Thursday and Friday looks generally dry and cold, though sleet and snow showers look likely across eastern Scotland and perhaps E England for a time. Xmas day still looking dry and cold after frosty start. A slow breakdown from the west to less cold air still indicated by GFS, UKMO and ECM either late on Sunday or on Monday, but the breakdown across the whole of the UK from the west, with snow preceding rain, keeps being put back by 12-24 hours. The angle of approach of the upper trough and frontal system all important to how quickly the cold air is eroded. More of a negative tilt (NW to SE aligned) to the approaching Atlantic trough/front – as the models seem to be trending, then the cold air will try and hang on across the north and east.

[The Enforcer]

What are the latest thoughts on where the snow will develop tonight? The radar seems to indicate that it could be further south than currently forecast - see line of precipitation highlighted on attached map:

Edited December 21, 2010 by The Enforcer

[The Enforcer]

12z NAE backs the Wales & W-E Midlands track shown by the BBC: http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=nae&MODELLTYP=1&BASE=201012211200&VAR=prec&HH=18&ZOOM=0&ARCHIV=0&WMO=&PERIOD=

12z NMM seems to follow the current precipitation pattern, extending down to the SE: http://www.meteociel.fr/modeles/wrfnmm.php?ech=55&mode=1

Edited December 21, 2010 by The Enforcer

[Nick F]

Tuesday late evening update

Snowfall begining to organise from Irish Sea across northern half of Wales, Cheshire, Shropshire, Staffs and the West Midlands. The snow is re-developing along an old occlusion that drifted north across the UK yesterday:

- this is due to upper forcing increasing ahead of an upper low moving east which is currently centred over the Irish Sea (see 500mb chart below):

Also seen by red-dashed lines representing 500mb geopotential height on current analysis:

NW extra 500mb vertical velocity charts for 9pm this evening suggest the mid-level forcing for ascent across N Wales, NW and central England this evening, enhancing snowfall along occlusion:

This upper low/cold pool will drift east across England and Wales tonight and tomorrow - so snow will redevelop east along the slow-moving occlusion as upper forcing increases eastwards.

18z GFS just out suggests 5-10cm generally across N Wales, Cheshire, Staffs, N and W Midlands between now and late Wednesday morning when it looks to die out - when the stronger forcing for ascent eases away eastwards. Snow further east but less heavy -perhaps 2-5cm across parts of the E Midlands across to Lincolnshire too.

18z NAE similar with area of snowfall, though gives larger totals in eastern England and well as Midlands, with total accumulations reaching 20cm in places and keeps snow going a few hours longer before dying out overnight.

So could be another day of severe travel disruption across these areas.

Elsewhere over the next few days, some patchy light snow possible tonight and tomorrow across other parts of England, especially SE England and E Anglia - but not amounting to much, temperatures are above freezing across SE England so a sleety mix here. Snow showers looks to increase across eastern Scotland and northeastern England tomorrow and are already brushing NE England coastline.

Thursday generally dry other than scattered snow showers near east coast of Scotland, hints of some wintry showers turning to snow inland across the far SE corner from 18z GFS thursday night and friday morning before dying out.

[Nick F]

Quick update, another 5 or 6 hours window for snowfall likely across a swathe of central UK between Welsh Borders across the Midlands to Lincs/Cambs/Norfolk. Before the upper forcing eases away east out across the North Sea this afternoon with snow faded away eastwards from England by early evening. A peppering of snow showers also across parts of eastern Scotland, especially around East Lothian and down across NE England likely to continue. A hard frost then likely to follow across northern and western areas where skies clear, with -10C perhaps over the snowfields over central and NW England and the Welsh Borders, perhaps falling to -15C or more over Scotland.

Tomorrow, still a few snow showers likely perhaps over E Scotland, otherwise mainly dry with a chance of sunshine away from the SE corner where a raw NE wind will likely bring cloud in off the N Sea. 00z ECM, UKMO and now 06z GFS joining to agree on a risk of sleet and snow showers feeding in across the far SE corner on the strong northeasterly wind later tomorrow and overnight into Friday, with the low over the near continent nudging a bit closers than on previous runs. So one to keep an eye on. Otherwise Friday and Saturday dry, cold and sunny by day with severe overnight frosts. Hints of thickening cloud bringing rain preceded by snow into the far west during Boxing Day, but some uncertainty how much inroads less cold Atlantic air will get into the UK. But it looks that it will remain, cold and dry over the Xmas weekend.