Wales Cymru Cold Spell Discussion

[Ukwoody]

pascal I thought you said your goodbyes on here yesterday, saying you wouldn't be back for a while!

woody

[benb]

Looks like it could turn to rain on its backege for coastal areas.

GFS looks all snow to me for South Wales:

http://www.wetterzen...cs/Rmgfs302.gif

http://www.wetterzen...cs/Rmgfs303.gif

NAE also looks good:

http://expert.weathe...011218_1112.gif < Upper air temps quite low

http://expert.weathe...011218_1112.gif

http://expert.weathe...011300_1112.gif

Great summary! I'm pleased/relieved that GFS seems to be moving towards a more snowy scenario (for most). The warmer air doesn't make too much progress and so it's a back edge rain rather than a front edge snow scenario. The front stalls and pretty much fizzles out. Living in SW Wales, I hope it continues to trend in this direction.

Can anyone with a good working knowledge of synoptics address the point above, I just cant see how this can deliver snow at sea level

It's a good question. Previously my essential ingredients for snow included at least -5c 850s and 528dam or less. Why is it that these are factors are not considered relevant in this situation?

Pleased to see only a very slight thaw today. The fields around the edge of the estuary at Pembroke are pretty green, but driving home it became apparent that all areas east of Kilgetty still have pretty much full snow cover. 2.8c in Pembroke at 4pm. 1.0c here at 5pm. The fresh snow that eventually settled last night is still on the ice on the drive. And, I'm not sure why, it does feel much colder today.

[bennytes]

Great summary! I'm pleased/relieved that GFS seems to be moving towards a more snowy scenario (for most). The warmer air doesn't make too much progress and so it's a back edge rain rather than a front edge snow scenario. The front stalls and pretty much fizzles out. Living in SW Wales, I hope it continues to trend in this direction.

It's a good question. Previously my essential ingredients for snow included at least -5c 850s and 528dam or less. Why is it that these are factors are not considered relevant in this situation?

Pleased to see only a very slight thaw today. The fields around the edge of the estuary at Pembroke are pretty green, but driving home it became apparent that all areas east of Kilgetty still have pretty much full snow cover. 2.8c in Pembroke at 4pm. 1.0c here at 5pm. The fresh snow that eventually settled last night is still on the ice on the drive. And, I'm not sure why, it does feel much colder today.

was delivering down around MH and Haverfordwest today. Amazing amounts of snow compared to around here. the main roads are fine, but the side roads and ESPECIALLY the country roads are thick. Still managed to get everything delivered though. even walked half a mile to one, that was at the bottom of a steep hill. It'll be impossible to deliver down there the next couple of days if they have a hammering.

[Jamie.]

Temp holding at -0.2C.

Has gotten colder through the Day with a NE wind.

It's very misty and it was either sprinkling snow or even drizzle ( :| ) earlier.

The ground is very damp in places where the lying snow had been cleared.

Not sure if it's all going to freeze over... cloud is keeping temps from falling away further.

[J10]

Great summary! I'm pleased/relieved that GFS seems to be moving towards a more snowy scenario (for most). The warmer air doesn't make too much progress and so it's a back edge rain rather than a front edge snow scenario. The front stalls and pretty much fizzles out. Living in SW Wales, I hope it continues to trend in this direction.

It's a good question. Previously my essential ingredients for snow included at least -5c 850s and 528dam or less. Why is it that these are factors are not considered relevant in this situation?

Pleased to see only a very slight thaw today. The fields around the edge of the estuary at Pembroke are pretty green, but driving home it became apparent that all areas east of Kilgetty still have pretty much full snow cover. 2.8c in Pembroke at 4pm. 1.0c here at 5pm. The fresh snow that eventually settled last night is still on the ice on the drive. And, I'm not sure why, it does feel much colder today.

Thicknesses are not as important in these situations, as there is embedded cold over the country. This is looking very good for a snow event for most, slightly more marginal on the coast as always. But I think our altitude makes a big difference.

This reminds me of 2 other situations Feb 96, where there was 18 inches of snow in Ebbw Vale, and 4 inches here, but next to nothing at sea level.

To a lesser extent the snow event in Feb 07, which gave 4-5 inches here and froze overnight to give a picture postcard scene however it rained then in the morning following.

Always cautious of these situations but if NAE says a says cover that's good enough for me.

In the models today it is very pleasing that the upper air temps remain below freezing for the duration of the event.

UKMO 12z also looks good.

Front running into upper air temps of around -2/-3C over South Wales- Snow seems likely in that case.

Today's models look very promising. and For Inland looks superb.

[Jimbob100]

Thicknesses are not as important in these situations, as there is embedded cold over the country. This is looking very good for a snow event for most, slightly more marginal on the coast as always. But I think our altitude makes a big difference.

This reminds me of 2 other situations Feb 96, where there was 18 inches of snow in Ebbw Vale, and 4 inches here, but next to nothing at sea level.

To a lesser extent the snow event in Feb 07, which gave 4-5 inches here and froze overnight to give a picture postcard scene however it rained then in the morning following.

Always cautious of these situations but if NAE says a says cover that's good enough for me.

In the models today it is very pleasing that the upper air temps remain below freezing for the duration of the event.

Today's models look very promising. and For Inland looks superb.

Are we likely to see any tonight do you think ?

[andy_leics22]

Right, because I have a lotta love for you Welshys and I am 90% likely to be in Aberdare in a few months time then I am going to do a forecast for what I think will happen tomorrow

I am not blowing my own trumpet here but I was pleased that I forecast the event you guys had before Christmas where places over 300m got pasted and places below 200m got hardly anything, mostly rain and sleet and wet snow.

I hope I get this right again

The main band of rain/sleet/snow should reach the likes of Swansea around or just after midday tomorrow. I would expect it to be rain/sleet/wet snow on the coasts probably not amounting to much although 5cm isn't impossible in heavy PPN even on the coasts if evaporative cooling takes place.

I think the main area that will get the best chance of deep snow is again areas above 250-300m in South Wales. Particularly Rhondda and the valleys. Low ground away from the coasts should still do well IMO, 60-70% chance of 10cm+ on low ground away from the coasts and 10-20cm above 250m-300m. Drifting a big thing to watch out for tomorrow too. There is going to be a strong wind and drifts could be upto 30cm+ in places where the most snowfall occurs. I'd expect the top of pen-y-fan to be absolutely pasted again. 20-30cm fresh level snow up there by Wednesday.

There is a chance that it could be a real disapointment tomorrow because of marginal uppers but the event before Christmas was a lot more marginal than this one so this time the snow gods should be on your side

Snowfall could last upto 12-18 hours aswell, it's going to stall around Wales and not move much for Tuesday afternoon/night and also Wednesday morning!

Edited January 11, 2010 by andy_leics22

[benb]

was delivering down around MH and Haverfordwest today. Amazing amounts of snow compared to around here. the main roads are fine, but the side roads and ESPECIALLY the country roads are thick. Still managed to get everything delivered though. even walked half a mile to one, that was at the bottom of a steep hill. It'll be impossible to deliver down there the next couple of days if they have a hammering.

And there was me thinking everybody else had all the snow! Just goes to show...

The most I've seen round here (aside from the moors) is up at Crosshands and on towards Carmel. Weds afternoon there was certainly at least a level 8" up there, possibly more. Anocdotedely, there's a not so level 12" on the Elvis Preselis.

Thicknesses are not as important in these situations, as there is embedded cold over the country. This is looking very good for a snow event for most, slightly more marginal on the coast as always. But I think our altitude makes a big difference.

This reminds me of 2 other situations Feb 96, where there was 18 inches of snow in Ebbw Vale, and 4 inches here, but next to nothing at sea level.

To a lesser extent the snow event in Feb 07, which gave 4-5 inches here and froze overnight to give a picture postcard scene however it rained then in the morning following.

Always cautious of these situations but if NAE says a says cover that's good enough for me.

In the models today it is very pleasing that the upper air temps remain below freezing for the duration of the event.

Today's models look very promising. and For Inland looks superb.

Yes the 850s certainly are a lot more favourable, in my opinion. On the current 12z, the 0c line barely touches the south of Wales. You can see it on this run from yesterday (I know it's not from the same run, but hey!) how the warmer uppers flood the south and west.

And now they don't...

The low is now progged to be a 150miles further west and drawing in a slightly more SE flow. Small but significant details, perhaps.

What was it about the GFS being over-progressive?

Hell, I just want a load of snow...

[CLH the red dragon]

I find the GFS hard to read for uppers but one of the other models (not sure which) which distributes numbers showed coastal uppers of about -4. So looking good.

[J10]

Right, because I have a lotta love for you Welshys and I am 90% likely to be in Aberdare in a few months time then I am going to do a forecast for what I think will happen tomorrow :lol:

I am not blowing my own trumpet here but I was pleased that I forecast the event you guys had before Christmas where places over 300m got pasted and places below 200m got hardly anything, mostly rain and sleet and wet snow.

I hope I get this right again :lol:

The main band of rain/sleet/snow should reach the likes of Swansea around or just after midday tomorrow. I would expect it to be rain/sleet/wet snow on the coasts probably not amounting to much although 5cm isn't impossible in heavy PPN even on the coasts if evaporative cooling takes place.

I think the main area that will get the best chance of deep snow is again areas above 250-300m in South Wales. Particularly Rhondda and the valleys. Low ground away from the coasts should still do well IMO, 60-70% chance of 10cm+ on low ground away from the coasts and 10-20cm above 250m-300m. Drifting a big thing to watch out for tomorrow too. There is going to be a strong wind and drifts could be upto 30cm+ in places where the most snowfall occurs. I'd expect the top of pen-y-fan to be absolutely pasted again. 20-30cm fresh level snow up there by Wednesday.

There is a chance that it could be a real disapointment tomorrow because of marginal uppers but the event before Christmas was a lot more marginal than this one so this time the snow gods should be on your side :lol:

Snowfall could last upto 12-18 hours aswell, it's going to stall around Wales and not move much for Tuesday afternoon/night and also Wednesday morning!

The uppers are less marginal than the event before Christmas, and to be honest they are not marginal for such situation , they are not zero or -1c for a start. Perhaps lower ground near coastal areas may miss out, but Elsewhere could do very well. NMM shows snow cover over all of Wales. Not often you see that.

[djwayne]

Any chance this snow is going to arrive earlier than planned as it seems to be closing on the uk pretty quickly from the sat images?

[J10]

Are we likely to see any tonight do you think ?

In Feb 1996, we had 36 hours moderate sleet and snow, with 4 inches at 150m near the coast, there was nothing at sea level, and 18 inches in Ebbw Vale. IMO the Valleys WILL see heavy snow, while other areas might see heavy snow.

And there was me thinking everybody else had all the snow! Just goes to show...

The most I've seen round here (aside from the moors) is up at Crosshands and on towards Carmel. Weds afternoon there was certainly at least a level 8" up there, possibly more. Anocdotedely, there's a not so level 12" on the Elvis Preselis.

Yes the 850s certainly are a lot more favourable, in my opinion. On the current 12z, the 0c line barely touches the south of Wales. You can see it on this run from yesterday (I know it's not from the same run, but hey!) how the warmer uppers flood the south and west.

And now they don't...

The low is now progged to be a 150miles further west and drawing in a slightly more SE flow. Small but significant details, perhaps.

What was it about the GFS being over-progressive?

Hell, I just want a load of snow...

It was, but we were right to be cautious as the GFS wasn't too far off the mark for the late December event. and the uppers were well above freezing, which stopped a snow event.

[benb]

Just had a look- it is coming in at a fair old whack!

It should slow down as it hits the block, yes?

It was, but we were right to be cautious as the GFS wasn't too far off the mark. and the uppers were well above freezing, which stopped a snow event.

[keithlucky]

Just had a look- it is coming in at a fair old whack!

It should slow down as it hits the block, yes?

It was, but we were right to be cautious as the GFS wasn't too far off the mark. and the uppers were well above freezing, which stopped a snow event.

And it's not 100% in the bag yet...

[NAOwillgetyou]

Just had a look- it is coming in at a fair old whack!

It should slow down as it hits the block, yes?

It was, but we were right to be cautious as the GFS wasn't too far off the mark. and the uppers were well above freezing, which stopped a snow event.

And it's not 100% in the bag yet...

Am I right in saying the slower the front takes to aproach the better for costal areas as it will give a more time to turn the rain into snow. I notice on the forcasts on tv they are now saying the front may not even make it as far as bristol.

Is it possible that it may not make it as far as cardiff and newport??

cheers guys

[benb]

And it's not 100% in the bag yet...

Suppose to reach us around mid day hoping it wont arrive until teatime.

[Snowyowl9]

How much snow has Hywel got now hope he isn`t snowed in was it 18inches last time he was on,the hills of Wales really are getting a battering this winter,with more to come.

Gone chillier now -0.5c

[keithlucky]

Suppose to reach us around mid day hoping it wont arrive until teatime.

Early or late would be best temps wise, it's still going to need all the help it can get around the coast!

Edited January 11, 2010 by keithlucky

[benb]

And it's not 100% in the bag yet...

Am I right in saying the slower the front takes to aproach the better for costal areas as it will give a more time to turn the rain into snow. I notice on the forcasts on tv they are now saying the front may not even make it as far as bristol.

Is it possible that it may not make it as far as cardiff and newport??

cheers guys

I think if the front arrives more slowly it demonstrates the high pressure exerting more influence and maintaing the cold air for longer- thus more chance of snow.

A stalled front means the warm air isn't making any further progress north east, so no thaw and the precipitation staying as snow before fizzling out- in theory!

Just watched Derek on BBC1- I think it's fair to say that they still aren't sure about this one either!

[J10]

The more is stalls the better the chance of snow as the colder air stays in place. Howeve this could minimise snow amounts.

The latest guidance would be from the NAE and UKMO 12 Hz.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=nae&MODELLTYP=1&BASE=-&VAR=rsum&HH=48&ZOOM=0&ARCHIV=0&WMO=

According to NAE no danger of precipiation not reaching SE Wales.

[Marcus_surfer]

Thicknesses are not as important in these situations, as there is embedded cold over the country. This is looking very good for a snow event for most, slightly more marginal on the coast as always. But I think our altitude makes a big difference.

Sure does, Here in Dunvant we have plenty of snow still, but down in the Mumbles, little if nothing.

[welshwizard]

i got a horrible feeling that this event could be rain for quite a few, as the temp outside does seem to be a few degrees above freezing now and if this arrives at 12 or 2 tomor it going to be even warmer.

my car is showing +2 so must be even warmer at lower levels, what temps are others getting as i am not sure if my car is correct.

[pyrotech]

Evening all,

Firstly can i apologise for such a poor forecast for Sunday / Monday

I predicted 3 cm for coastal areas and up to 15cm for favoured areas in Wales.

Well percipitation was poor, Wind was much less than forecast and cardiff had a snowfall that resembled dandruff at best.

Mid wales did fair a little better with signifigant Snow at Newtown.

So this week now.

The whole event for Tuesday is marginal but the right side of Marginal.

850s temp and 2m temp are just right for snow , Thickness is not but its not so critical in this set up.

Dew points look fine

West Wales will quickly whiten up following south west England, Cardiff may see sleet before it too sees heavy persistant Snow.

Winds again are set to increase and i have more confidence in both wind speed and percipitation amounts.

Coastal areas most likely to be effected by modified air from Bristol channel, Tommorrow evening this could increaese snowfall amounts but later on it will take it beyond marginal from the west.

Snow Amounts depend how quickly north this moves but here is my thoughts for the situation as it looks tonight

Swansea and swansea Valleys 4 - 6 inches possible sleet near coast later

cardiff 4-8 inches possible sleet to start then snow till Wednesday day time.

Merthyr 6-8inches with drifting snow and high routes closed due to conditions, A470 brecon Beacons could close for a time from blowing snow.

This is same for eastern parts of high ground including gwent valleys.

The actual track of the low is imperative and so changes are likely, it can not be ruled out for a sleet event for coastal areas throughout but latest NAE is not showing this at the time of forecast.

This is the way that w normally get our heavy but short lived snowfalls and i am not convinced that an upgrade will yet occur, this is more likely than a rain event so i would not be surprised to see 30cm somewhere over the next 36 hrs

Edited January 11, 2010 by pyrotech

[Matt00011]

Swansea and swansea Valleys 4 - 6 inches possible sleet near coast later

cardiff 4-8 inches possible sleet to start then snow till Wednesday day time.

Hope your right. Only time will tell.

[J10]

i got a horrible feeling that this event could be rain for quite a few, as the temp outside does seem to be a few degrees above freezing now and if this arrives at 12 or 2 tomor it going to be even warmer.

my car is showing +2 so must be even warmer at lower levels, what temps are others getting as i am not sure if my car is correct.

Temperatures are likely to fall back a little tonight, and not rise that much tomorrow.

The snow is also set to last for quite a while as well, and much of the heavier stuff is set to fall in the early hours.

However, it would help if the cloud were to clear tonight, to lower the temps as much as possible.