Model Output Discussion

[Ben_Cambs]

Todays GFS 12z still goes for snow on the North and North Western Flank of the LP on Tuesday into Wednesday. Snow showers will affect Scotland from Monday then NI by Tuesday. Dew points will not be favourable at first for snow in England on Tuesday, even for the high ground:

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=gfs&MODELLTYP=1&BASE=-&VAR=taup&HH=72&ZOOM=0&ARCHIV=0&WMO=

Then the Colder Arctic air heads south from Scotland:

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=gfs&MODELLTYP=1&BASE=-&VAR=taup&HH=78&ZOOM=0&ARCHIV=0&WMO=

Begins to turn to snow over the North of England by the evening, though still mildish over Eastern England. Snow becomes more widespread over Central areas and Wales by midnight:

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=gfs&MODELLTYP=1&BASE=-&VAR=taup&HH=84&ZOOM=0&ARCHIV=0&WMO=

PPN type chart: http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=gfs&MODELLTYP=1&BASE=-&VAR=rart&HH=84&ZOOM=0&ARCHIV=0&WMO=

Colder uppers cover all of the UK by the early hours of Wednesday, many areas would of seen or be seeing snow by this point:

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=gfs&MODELLTYP=1&BASE=-&

VAR=rart&HH=90&ZOOM=0&ARCHIV=0&WMO=

The front clears by Wednesday lunchtime from the East coast, leaving scattered wintry showers in its wake. A lot of PPN will of fallen by this point, up to 65mm in the North Pennines by this point.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=gfs&MODELLTYP=1&BASE=-&VAR=rsum&HH=90&ARCHIV=0&ZOOM=0&WMO=

I suspect if this run did pull off, the Northern Pennines would be worst affected by this, with quite a few inches possible over higher ground. Accumilations over low ground will be temporary and will melt as soon as the snow stops falling. Snow becomes increasingly confined to Scotland by the end of the week. This is all based on the GFS 12z

[reef]

General Cold Spell Discussion:

[Cheese Rice]

Don't really like the GFS the low goes too far north, although we would still get the snow I would prefer the low to be further south.

Surprising BBC forecast, "significant snow even down to lower levels", the snow graphics on Monday covered West/North Yorkshire and parts of NW England Tuesday showed snow over much of Northern England. I do think some if not all are under estimating the snow potential.

[frostyjoe]

hurray an upgrade with temps on monday being 3-4c and no 6c like before... and snow heading further north this time.. shall see how bbc put this.. btw the charts show me getting snow showers by monday 12pm.

[Cheese Rice]

General Cold Spell Discussion:

http://forum.netweat...ell-discussion/

Thanks, would this replace the regional threads? I would prefer the regional threads not to open as I can't imagine there been that many posts even if it does snow.

[Frosty.]

Good agreement from the models that next week will be on the cold side and very unsettled with lots of rain across the uk and even some wet snow in central and northern britain, it's more likely that northern scotland will be coldest with wintry showers from tomorrow onwards but if the ecm 12z verifies, all of britain will be cold and disturbed with low pressure in control for the next 10 days at least.

[Ben_Cambs]

What I'm wondering is what usually happens in the situation that we are currently in. Its currently GFS v UKMO and ECM for widespread snowfall as the LP brings in more fronts on GFS. I remember the projected Easterly for the beginning of the month was first shown by GFS then ECM and UKMO followed, but then GFS backed off this solution and was the eventually the right model. I fear that because ECM first showed this northerly and has since backed away from snow for a widespread area, that it may be the eventual winner?

[Thundery wintry showers]

The latest set of model runs have sent the main focus of low pressure further west, so the chance of snow is reduced, while the chance of cold cloudy weather persisting through to at least midweek has increased, because that low will have embedded fronts associated with it. I think next week will be a washout if the ECMWF comes to fruition, while GFS looks less extreme, and UKMO more showery with low pressure centred to the north rather than on top of Britain.

There may be further twists and turns to come, however.

[phil nw.]

Todays GFS 12z still goes for snow on the North and North Western Flank of the LP on Tuesday into Wednesday. Snow showers will affect Scotland from Monday then NI by Tuesday. Dew points will not be favourable at first for snow in England on Tuesday, even for the high ground:

http://www.weatheron...0&ARCHIV=0&WMO=

Then the Colder Arctic air heads south from Scotland:

http://www.weatheron...0&ARCHIV=0&WMO=

Begins to turn to snow over the North of England by the evening, though still mildish over Eastern England. Snow becomes more widespread over Central areas and Wales by midnight:

http://www.weatheron...0&ARCHIV=0&WMO=

PPN type chart: http://www.weatheron...0&ARCHIV=0&WMO=

Colder uppers cover all of the UK by the early hours of Wednesday, many areas would of seen or be seeing snow by this point:

http://www.weatheron...LLTYP=1&BASE=-&

VAR=rart&HH=90&ZOOM=0&ARCHIV=0&WMO=

The front clears by Wednesday lunchtime from the East coast, leaving scattered wintry showers in its wake. A lot of PPN will of fallen by this point, up to 65mm in the North Pennines by this point.

http://www.weatheron...V=0&ZOOM=0&WMO=

I suspect if this run did pull off, the Northern Pennines would be worst affected by this, with quite a few inches possible over higher ground. Accumilations over low ground will be temporary and will melt as soon as the snow stops falling. Snow becomes increasingly confined to Scotland by the end of the week. This is all based on the GFS 12z

A well presented post and i agree with your last para.

It really underlines why the excitement over snow this late in the season passes me by.

The ECM not keen on bringing the really cold air South as it stalls the Low over England midweek,

http://www.wetterzentrale.de/pics/Recm961.gif

Undoubtably it will get colder next week,but detail on any snow not yet certain by any means.

[Terminal Moraine]

The 12z for the precip Mon-Wed has another change, its split the fall into 2 distinct time periods, something the 06z had started, 15mm Mon 03z-Tue 03z and 21mm Tue 09z-Wed 09z

The overall trend in the total continues downwards, its now 36mm from the 64mm on the 18z yesterday.

Yes, I noticed that. The figures for my area are 23 and 26mm respectively, a total of 49 mm which is very similar to the 06z but down on the 18z yesterday.

The Met' Office seem to think the fronts will move north more slowly as they have extended their weather advisories southward into the Midlands; yesterday Derbyshire was the southern limit of the advisory.

The fax chart shows the warm front moving quite slowly north during Monday and then a kink developing on it as a depression develops; it's this which is expected to provide the bulk of rain as it deepens and moves slowly east.

The front occludes and is eventually dragged slowly east behind the depression during Tuesday and into early Wednesday, cold air cutting in behind it.

I'll be interested to see what the GFS does over the next few runs.

[frostyjoe]

just looked at the updated bbc forecast and they are still forecasting 9c for wednesday and 7c for thursday... the gfs says 4c... most of the time... will this be updated in the morning?? do they follow gfs?

[Cheese Rice]

just looked at the updated bbc forecast and they are still forecasting 9c for wednesday and 7c for thursday... the gfs says 4c... most of the time... will this be updated in the morning?? do they follow gfs?

No they don't follow the GFS, the forecasts are from the meto that use UKMO and ECM (?) they are computer generated so there is no human input. Anyway 9.c can easily be achieved with -5 850's due to the sun been warmer, the reason why other areas may see lower maxes is because there will be alot of cloud around suppressing temps. I don't know why you take so much notice of the 5 day forecast as they are rarely correct, having said that the forecast for me seems fairly accurate. http://news.bbc.co.u.../2535?area=LS16

Edited March 27, 2010 by 10123

[ANYWEATHER]

A knifedge situation regarding lowland snow on Tuesday, but certainly lying snow possible at some altitude and given any heavy precipitation there is no reason why snow wont lie on low ground once the cold air tucks in. Certainly interesting model watching over the next few days..... Blue highlighted map shows where the likely snow will fall [according to the 12zgfs and likely to change] and remember elavation and Evaporative cooling will be the key to snow falling and even settling!! :excl:

[frostyjoe]

No they don't follow the GFS, the forecasts are from the meto that use UKMO and ECM (?) they are computer generated so there is no human input. Anyway 9.c can easily be achieved with -5 850's due to the sun been warmer, the reason why other areas may see lower maxes is because there will be alot of cloud around suppressing temps. I don't know why you take so much notice of the 5 day forecast as they are rarely correct, having said that the forecast for me seems fairly accurate. http://news.bbc.co.u.../2535?area=LS16

Yes but the gfs and most other sites say 3-5c most of the week .. I'd say they will update in morning

[yamkin]

WMC 12Z is showing cold uppers

PS.....It would be an idea to open the regional thread section

[BlueHedgehog074]

@10123: Wow, you've really got it good.

It does seem like there is going to be quite a battle with the cold, snow, cool and wet weather next week. Shame about the lower snow risk for Tuesday with the newest update, and I suppose with the Low Pressure being in a less favourable area sort of delays some very cold winds reaching Southern and/or Eastern parts. I still feel reasonably confident, however, about getting something wintry, but perhaps just not from the Low on Tuesday; well, maybe towards the evening or overnight.

I wonder what the next update will show?

@yamkin: That's encouraging.

Edited March 27, 2010 by Rainbow Snow

[NorthantsSnow]

The 18z has watered down the uppers somewhat for Tuesday night. As a result I would suggest wrong side of marginal on this one for a lot of people at low level altitudes.

18z http://charts.netweather.tv/gfsimages/gfs.20100327/18/75/h850t850eu.png

12z http://charts.netweather.tv/gfsimages/gfs.20100327/12/81/h850t850eu.png

It's a lot messier the flow. Hopefully not a trend.

[frostyjoe]

The 18z has watered down the uppers somewhat for Tuesday night. As a result I would suggest wrong side of marginal on this one for a lot of people at low level altitudes.

18z http://charts.netweather.tv/gfsimages/gfs.20100327/18/75/h850t850eu.png

12z http://charts.netweather.tv/gfsimages/gfs.20100327/12/81/h850t850eu.png

It's a lot messier the flow. Hopefully not a trend.

That's only for England

[Cheese Rice]

GFS continues the downgrade for this area, all because the low is projected further north. I would say 5-7cm likely for Leeds which is fairly good but not a patch on what was shown a few days ago.

Edited March 27, 2010 by 10123

[damianslaw]

Still uncertainty with regard to the exact path of the low on Monday dn Tuesday which will make all the difference in terms of where is likely to see snow and where isn't.

In marginal situations, it is going to be a case of nowcasting and watching where the front decides to travel as well as seeing how heavy the precipitation gets. In this context guessing at this stage where any snow is likely to fall at low levels is never going to be attached with any great certainty. As I said in my last post areas with a bit of height to the north and north west of the front will be best placed especially those parts which catch the heaviest precipitation - just where this will be well we will just have to wait until the event is underway.

Back to the models, GFS seems to be downgrading the intensity and longevity of any snow/rain also wants to take the low on a slightly more northerly path than ECM and UKMO - however, all are in agreement that it will eventually leave the country via the North Sea with a developing shortwave feature to the north west heralding the makings of another low come Thursday. The easter period remains far from certain - though the general theme looks to be a fairly unsettled one with cooler conditions rather than mild.

[kold weather]

Very marginal set-up coming up which needs to be perfectly timed if you are to get snow from it....still there is a risk of snow on higher ground looking at things, esp on the backend of the front, but for most of those at lower levels, I'd imagine at this time of year we'd probably be the wrong of marginal in this sort of borderline flow.

Still the flow looks unstable on Wednesday, so we'll probably see fairly widespread wintry showers anyway.

[LomondSnowstorm]

This seems very much like the system that brought record snow to inland Scotland above 100m which was initially progged for the Midlands - perhaps the wrong side of marginal here if it northgrades any more but if it stays where it is currently - jackpot!

[Derp Patrol]

As I expected, this projected cold spell is now starting to be downgraded. In the south, I would not be surprised if temps still reached double figures, which is what I would prefer. I never expected any snow from this anyway. Snow down here is hard enough to get in winter, but virtually impossible by the time April comes around. Signs of an azores ridge at the end of the run, which is a good sign for those of us like myself looking for warm, sunny weather :lol:

[BlueHedgehog074]

Beginning to think that Wednesday, with some generally decent 850 hpa high-up temperatures would be a better day for the Midlands to see snow/wintry weather, though there is still a chance I feel for some ares to see snow at high and low levels around Tuesday night time. Clearly, some Western/North Western and hilly areas could receive some wintry weather earlier than that with slighly more favourable dom's and high-up temperatures. Perhaps not the most inviting Dewpoints for the start, though are looking better for around 72 hours onwards on the GFS.

The Met Office outlook/forcasts seem promising, also, for some rain, sleet, and snow for part of next week, (hopefully some good snowy/wintry showers for Wednesday with the cold 850 hpa high-up temperatures + slight storm risk).

Even though there appears to have been some lowered snow potential, and with the fact that Wednesday's higher snow risk could become lowered, I think there is still certainly enough time for modifications and ajustments with possible Low shifting and that. The overall forcasts/maps are looking tolerable and at least North and Western areas, as well as the South and Eastern areas later on, have chances of wintry events to look forward to. Idealy, it would be great to see a one-day widespread snowfall event before the cold weather gives up the ghost for Summer (who knows, the next few updates could bring back the potential).

In fact, may avoid looking at the forcasts/maps/charts during today; the excitment is really starting to get too high with the snow constantly on my mind...

Edited March 28, 2010 by Rainbow Snow

[snowmadchrisuk]

Tuesday is not looking like a Snow day for anybody out of Scotland on the latest charts. The South looks like it may even be dry. Snow showers now showing for Wednesday but I have low confidence on that given this is all constantly changing and downgrading.