ECM12 has me down for a foot of snow falling in 12hrs at around 150 hrs. So you can pretty much discount this run completely! 

FAO Saint Snow. 

(And Doc). 

How do you get Exeter on that instead of Plymouth?

Exactly ! I bet when the 00z come out early tomorrow this will all revert back to zonal or mild etc or less cold and blocked. I knew that the 18z will be and upgrade ....it seems to be the case. Now let's see if the ECM will follow this trend!? FINALLY?

Plus 72 hours on the GFS. First chance of snow outside of scotland/high ground? Occluded front brings a period of rain/snow to most parts, its very marginal although I suspect most places will see snow flakes out of this. Behind the air is very unstable and showers are likely to gather. By tuesday evening the convective instability will be extremely high. I'd expect showers to be pretty much everywhere.

Yes I saw his forecast it's so strange how he mentioned that there was a lot of uncertainty about Tuesday's snow' or weather event but then left an outlook saying that from midweek on wards until end of week it 'looks' as if it will turn milder!? As in he is more confident about the longer term forecast but not 3 days away? :D

GFS 18z is better but there is still great uncertainty later next week and it could well turn milder. Don't think it will be settled for days.

I find the psychology of the hunt for snowy weather to be fascinating not particularly posters on here but elsewhere. It has been said many times this year that the 12z models are good for cold and then the 00z are usually poor. I think it is all in the head. Take tonight. ECM and UKMO operationals show it probably turner milder at the end of next week as the position of the low isnt favourable. GFS has come along with a better 18Z run  raising the mood and expectations but we cannot forget the ECM and ensemble uncertainty. I have now seen comments now expressing surprise that the BBC weather are saying it might become milder at the end of the week - well that is what the ECM shows. Also MOGREPS too - via Met office automated.

Anyway a fascinating few days to come it could go either way . I think less cold weather will probably  edge it unfortunately.

I won't post all the precipitation charts as it's difficult to forecast it beyond a day or too accurately let alone the type and i know the models over cook the precipitation charts ...however as things stand it looks like some sleety showers early Sunday for the SW and then again Monday night into Tuesday and more persistent snow from Tuesday afternoon into evening for the south and south west:

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THEN MORE SNOW ON WEDNESDAY FOR THE South West:

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Thursday night becoming rain and then turning back to snow again on Friday as frontal system stalls and then slips southwards:

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I could go on but it's becoming more unreliable!

HOWEVER - AS you can see there are at least 2 or 3 snow opportunities for the south west and south in general - more prolonged snow next week and I should be gutted if not one snowfall came about!

FINGERS CROSSED.

I wonder what the OOz will bring?

GFS Parallel throws up snow on Sunday for the east and then brings the snow on Tuesday further north, 

Always the case but it is a fact we usually wake up on a low watching the 00z run and then everything builds up and then we get let down again by the following day etc. After the  GFS 12z run which ended on a slack westerly at +384 the 18z run ends on an easterly @ +384! -See difference below it's another major flip at end: - It's been like this on and off now for several days in FI and maybe one day this will come about! But the difference is noticeable below between the GFS 12z & 18z OP runs..

12z

18z:

You couldn't make it up could you? As I may have said - Whilst I expect some model wobbles and downgrades and upgrades - in the year's I have been winter model watching I have never seen so much flip flopping from run to run ever! It';s like hopes are raised and then dashed each run!?

ANYWAY, But even , and a capital E - even if it did turn milder which the BBC forecast for week ahead - it won't be for long because so many longer range output's have gone for a cold blocked February and the Met Office update said about the outlook during next 6 -30 days and they have been very confident about this:

UK Outlook for Wednesday 30 Jan 2019 to Friday 8 Feb 2019:

Sunshine and wintry showers on Wednesday, with these becoming more confined to eastern and perhaps southern areas. Otherwise, some sunshine around, before cloud and outbreaks of rain and hill snow will move into the west by the end of Wednesday. This will move east into Thursday, maintaining this changeable and at times unsettled and predominantly cold spell of weather. Snow is likely to lower levels at times, perhaps more so than during the cold weather so far as low pressure systems take a more southerly track towards Biscay, with overnight frost and ice remaining a risk too. There is still a small chance that even colder conditions may develop during early February with easterly or northeasterly winds dominating, bringing an increased possibility of disruptive snow.

UK Outlook for Saturday 9 Feb 2019 to Saturday 23 Feb 2019:

Cold or very cold conditions are likely to dominate the weather throughout this period, with a greater than average chance of easterly or northeasterly winds dominating.

Given the level of uncertainty I would say that anything in the models past the middle of next week is suspect.  The BBC News24 forecast at 23.27 stressed the uncertainty about the potential for rain or snow next Tuesday and described the uncertainty over the track of the low pressure later next week: less cold is an option (as per GFS and ECM) but it may be another short-lived blip.

18z ensembles for London:

Usually there are always a few but not in this case!

Not one ensemble is going at or below -10c @ 850hpa in FI except the control run - (which is of course an outlier).

The charts are hardly worth looking at beyond 7 days even in normal times; at the moment I'd take 2-3 days off.

The LP potentially running close to the south is a good example: that wasn't even seen as a real risk even 24 hours ago. That's fewer than four days away.

The Met Office has been very consistent in its longer range forecasts that milder weather could make inroads into the south at times. But, as you say, they've also been quite consistent in predicting a predominately cold or possibly very cold outlook.

The 18Z parallel is extraordinary snowy. Some potentially dangerous snow amounts on that.

It really shows how a slight change in the geometry of the low can make a large difference. I wouldn't rule anything out from 'no snow at all' to 'more snow than last march' to anywhere in between.

There is a real potential here for alot of frontal snow and convective based snow. 850hpa temperatures are not that low but that doesn't matter at all, on the 27th December 2010 it snowed with 850s at +2C. What's far more important is establishing a cold airmass close to the surface. Two things that will really help are:

Snow cover

Light winds

And there are periods of both snow and slack winds for cold air to start developing near the surface. The more snow cover we get the easier it will be for snow to fall later. We can start to build up the first elements of this snow cover tonight in NW scotland.

For the sake of balance I would also add there is also a potential for not enough snow cover to be built up, winds to generally be too strong or importing air in off the sea and for the entire event to be a watery, sleety dud. The wind being a little lighter, the temperature being slightly colder or the precip being slightly heavier could make all the difference.

Good summary. Lots of potential but I don’t think it will be clear until possibly a few hours before if it’s marginal.  The precise track, intensity and speed of movement are key, along with the issues you’ve flagged.

It will change but as an example the snow depths from the 18z parallel:

I think they are sticking there neck out there.  Still a fair chance that that could happen as reflected by the models for the period in question.  It is a given from the main models that the low that approaches on Wednesday will either reach or cross the Greenwich Meridion during late week.  With that assumption IMO it is not the north/south positioning that is important.  It is reaching us within the cold air so continued wintriness is more a factor of the depth and intensity of the system.

Yes you made some good points Q! Thanks!

BTW where are you located at can I ask?

UKMO a snow low for the south @96:

PARA has similar channel low at 96h. Infact much improved output all round this morning good start to the 0z.

ECM blows up the low at 144h but looks isolated in doing this this morning .

Nothing new for your location though Jacko

I think this is a fair enough summary but with a little luck some snow is possible in places (here not being one of them...just to frustrate Richard).

(Incidentally I would expect parts of the Highlands to remain subzero for several days in the forecast setup with snow cover.)

Clearly quite a bit of uncertainty this morning, I think most of us were expecting to wake up to see that the other models had followed the ECM milder solution of recent runs.

The fairly cold outlook, with marginal snow chances, increased with latitude and altitude continues within the reliable, with signs of a slight warming into February.  It would be ironic indeed if the FI signs were correct for once this winter, which has gotten started this week, with frosts and snow.  There was 7cms on the ground on the northern outskirts of Dover on Wednesday morning, some of which which was still in evidence yesterday afternoon.

It will be a very interesting week, tracks of lows will be critical and forecasting a nightmare.  I really enjoy these nowcast situations, a 3 hour look ahead.

Meanwhile The ICON looks interesting a week away - theres a chance of heavy marginal wet disruptive snow, great fun!