Greenland Express: Snow showers possible from Monday night

nacho libre · 12-01-2018 8:29pm

Gaoth Laidir wrote: »

"just get cold rain and sleet"...

Now that seems familiar.

I think this time we will have snow and some modest accuulations of snow will occur at lower levels. I would love if we all got 36 inches of snow that lasted for a few days. Although the mods might not as civil war might break out on here:)

catrat12 · 12-01-2018 8:30pm

Will the Dublin mountains see anything sorry for asking twice

nacho libre · 12-01-2018 8:43pm

catrat12 wrote: »

Will the Dublin mountains see anything sorry for asking twice

There is nothing to be sorry for. I think, given the wind will be strong, the Dublin Mountains will see some snow. Errigal is the place to be though if you want to see a lot of snow on the ground. The Wicklow mountains will be good too.

Oneiric 3 · 12-01-2018 8:47pm

nacho libre wrote: »

I think this time we will have snow and some modest accuulations of snow will occur at lower levels. I would love if we all got 36 inches of snow that lasted for a few days. Although the mods might not as civil war might break out on here:)

Couldn't find a proper snow dance but here is the next best thing.

https://www.youtube.com/watch?v=TQkiANhoZCk

Hopefully upon hearing the allure of this tune, that the skies will dance along accordingly.

sryanbruen · 12-01-2018 9:11pm

average_runner wrote: »

Don't think it has gone above 10C in dublin all week!!

I've had only one day this January so far with a maximum of 10c or more.

fraxinus1 · 12-01-2018 9:34pm

nacho libre wrote: »

M.T. Cranium is more conservative these days because in the early days, he would talk up snow chances and often times we would just get cold rain or sleet. He tended to be influenced by the prevailing mood on here too.

I can't fathom how someone can say winter is over already- unless you are engaging in reverse psychology?? You, as you have mentioned are longer in the tooth than i am, so you should know well that January and February is our optimum time for snow- just ask any farmer, if you don't believe me. So taking all this into consideration, i believe you are secretly doing a snow dance to the weather gods that we get snow next week.

If a snow dance works, I would do one. I want snowfall. Even just for a day or two.

George Sunsnow · 12-01-2018 9:39pm

fraxinus1 wrote: »

If a snow dance works, I would do one. I want snowfall. Even just for a day or two.

But you’re in Donegal,the snowiest county in the planet

Kermit.de.frog · 12-01-2018 10:08pm

Ok so where are we?

On track.

On Monday morning the northwest flow becomes well established quickly. Temperatures begin the day 6 - 10c country wide but will fall back through the afternoon. By early evening temperatures across the Northwest and North Midlands will be struggling to between 1 - 3c.

Showers start early and become widespread quickly in a strengthening northwest wind. Showers will mainly be of rain through the afternoon but later (and quickly) they will start to transition to snow in the northwest and west. By nightfall settling snow is likely in the northwest and parts of the north midlands to low levels.

Dew points by Monday evening

78-101UK.GIF?12-12

On Monday night snow showers are heavy and frequent in Connaught and Ulster spreading inland but lighter in the midlands and east (the flip side of this is the midlands and east will be the coldest regions with temps generally around freezing so any snow that makes it through will settle comfortably here). Munster may see more sleetiness for a while overnight. Temps slightly higher here - up to 3c.

On Tuesday - it will be very cold with widespread heavy snow showers causing drifting and occasional blizzard like conditions in the west and north and the real possibility of some disruption in Leinster and Munster also through the day. Showers driven a long on a nigh on gale force Northwest wind. 2 - 6 cm over the east and south. 10 - 12 cm over the west and northwest.

Temperatures 0 - 3c, warmest over Munster.

Snow and hail showers, widespread at times, continue Tuesday night. Wind will die back a little and so it will be very cold. Lows 0 - -3c (coldest in the east).

Further widespread accumulations.

On Wednesday morning and afternoon sleet and snow showers continue but will die out toward nightfall.

Temperatures once more ranging 0 - 3c on Wednesday.

Frontal system will approach from the Atlantic possibly Wednesday night and we need to watch this as it squares up to the embedded cold air over the country. Ripe conditions for snowfall particularly over the northern half of the country.

We have to leave it here for the moment as there is uncertainty regarding the timing and extent of this incursion and it's overall effect. Key for snow is we don't want that to deepen too much, we want it just right.

It will remain very cold.

Wrap up!

More later.

mickger844posts · 12-01-2018 10:18pm

I would be pleased enough with Kermits latest update. In Waterford City surprisingly we do quiet well with a NW flow. It wouldn't surprise me in the slightest to see at least a covering of some sorts IMBY. Fun times hopefully

derekon · 12-01-2018 10:34pm

Hi Kermit, thanks for the post and the work you put in with charts etc.

Just to check, would you agree with my view that the greater Dublin region will only get cold rain or at best, sleety showers with NO settling snow?

D

Gaoth Laidir · 12-01-2018 10:36pm

This back-trajectory plot shows the source and trajectory of the air arriving at Knock airport at midnight Tuesday night, plotted for two heights (50 (red) and 1500 (blue) metres amsl). So the airmass at Knock at midnight on Tuesday will have originated over Baffin Bay/northeastern Canada and taken a 3000-km sea track around the southern tip of Greenland towards us.

Sea surface temperatures (click map to zoom in) between Greenland and New Foundland are around 3 °C, rising to around 9-11 °C from about 25W. This is a lot of scope for modification, so I don't think we'll see surface dewpoints much below zero by the time it arrives at our shores. Current dewpoints in the source area are around -30 °C.

Further north will always be slightly colder, further south warmer, but in such a convective setup, with the coldest uppers north of Ireland, it will be a rogue shower that produces 100% snow at lowest levels away from the far north imo.

Now the other disturbance mentioned for Wednesday could be a different story.

pauldry · 12-01-2018 10:45pm

Still looks like widespread wintry showers which at worst will bring continuous hail sleet and snow with some covering at times

At best a blanket of snow Monday night in most parts of the North and West....n of course the rest of Ireland too

Gonzo · 12-01-2018 10:47pm

derekon wrote: »

Hi Kermit, thanks for the post and the work you put in with charts etc.

Just to check, would you agree with my view that the greater Dublin region will only get cold rain or at best, sleety showers with NO settling snow?

D

I think the main issue will be will the showers make it this far and how heavy will they be. Nighttime would be the greatest opportunity for lying snow but at night the showers tend to become more confined to the west and north. I still think it's currently too early to tell what will happen.

Kermit.de.frog · 12-01-2018 10:48pm

derekon wrote: »

Hi Kermit, thanks for the post and the work you put in with charts etc.

No worries!

Just to check, would you agree with my view that the greater Dublin region will only get cold rain or at best, sleety showers with NO settling snow?

D

I don't agree, I think Dublin will see snow from this and it's liable to settle in places as well particularly on Tuesday.

Clonmel1000 · 12-01-2018 10:49pm

Well as someone with a daily 200km commute I really hope this doesn’t come to pass. I suspect it won’t but a couple of iffy days this week with ice frost and fog.

nacho libre · 12-01-2018 10:56pm

fraxinus1 wrote: »

If a snow dance works, I would do one. I want snowfall. Even just for a day or two.

Prove it. You have turned your back on snow so many times here, i don't blame snow if it now turns its back on you:(

...but seriously you should see a bit of snow this week. I will hopefully be looking on enviously at the snow pictures on here next week.

Larbre34 · 12-01-2018 10:56pm

I'm afraid Kermits I don't agree with Kermits interpretation of the charts .

MOD Changed the wording of your post

In his selective chart posting, he omitted the upper level temp charts for any of the period under discussion, they never exceed -6C at 850, which would be marginal enough in an E/NE'ly situation, but in an atlantic system with a long fetch - albeit polar maritime - they are basically curtains for snow on all but high ground in the north west and north. What we are looking at is showery weather countrywide, passing hail, an irritating windchill feeling like 0-2 degrees, night frosts in sheltered parts and generally unpleasant to be outdoors in without being well wrapped up.

In other words, don't get your kids hopes up over the weekend.

Kermit.de.frog · 12-01-2018 11:03pm

Larbre34 wrote: »

they never exceed -6C at 850

Are you sure?

I'm perfectly comfortable with the forecast and expect the warnings in due course.

The hits are fine, makes people happier when it snows

munsterlegend · 12-01-2018 11:03pm

It will be an interesting weeks weather anyway no matter what happens. We usually get plenty of precipitation from a north westerly here in north cork but it's usually of the very wet snow variety at best unless at high level so not expecting too much.

nacho libre · 12-01-2018 11:06pm

Larbre34 wrote: »

.

In his selective chart posting, he omitted the upper level temp charts for any of the period under discussion, they never exceed -6C at 850, which would be marginal enough in an E/NE'ly situation, but in an atlantic system with a long fetch - albeit polar maritime - they are basically curtains for snow on all but high ground in the north west and north.

In other words, don't get your kids hopes up over the weekend.

That is not quite true in this scenario, the thickness factor and the dew points are on the right side in this situation, also while it is a long fetch, the wind could play a determining role this time in helping to both cool the water and hasten the track, which will help in reducing the modification factor. If the charts don't downgrade between now and monday, lower levels in the north and west will see snow. Philip Avery- the bbc forecaster- seems to think there will be snow next week as well. Wednesday looks interesting according to him for some northern areas.

Gaoth Laidir · 12-01-2018 11:16pm

nacho libre wrote: »

That is not quite true in this scenario, the thickness factor and the dew points are on the right side in this situation, also while it is a long fetch, the wind could play a determining role this time in helping to both cool the water and hasten the track, which will help in reducing the modification factor. If the charts don't downgrade between now and monday, lower levels in the north and west will see snow. Philip Avery- the bbc forecaster- seems to think there will be snow next week as well. Wednesday looks interesting according to him for some northern areas.

Even the GFS has only a brief passing 520 dam thickness in the north late Tuesday, which is not quite the 516 I'd be hoping for to guarantee snow, except in the heaviest showers.

The wind will not cool the sea by any amount, but it will hasten the track. Still, it has about 30 hours over waters from 3-11 °C. North will be best for low levels, but even then I would reckon only in the heaviest showers.

Anyway, it is what it is. I hope to register more than I did this time last year...

nacho libre · 12-01-2018 11:28pm

Gaoth Laidir wrote: »

Even the GFS has only a brief passing 520 dam thickness in the north late Tuesday, which is not quite the 516 I'd be hoping for to guarantee snow, except in the heaviest showers.

The wind will not cool the sea by any amount, but it will hasten the track. Still, it has about 30 hours over waters from 3-11 °C. North will be best for low levels, but even then I would reckon only in the heaviest showers.

Anyway, it is what it is. I hope to register more than I did this time last year...

You don't need 516 to get snow here, of course the lower the thickness the better, i have often seen snow in sub 528 dam thickness. As i keep saying i'm not expecting a foot of snow courtesy of a blizzard. So if that is your criteria for this then you will of course be right. I think we will get 2- 3 cms of snow at lower levels widely in the north west, i will concede that you were right in your analysis if this does not happen.

Shedbebreezy · 12-01-2018 11:33pm

nacho libre wrote: »

You don't need 516 to get snow here, of course the lower the thickness the better, i have often seen snow in sub 528 dam thickness. As i keep saying i'm not expecting a foot of snow courtesy of a blizzard. So if that is your criteria for this then you will of course be right. I think we will get 2- 3 cms of snow at lower levels widely in the north west, i will concede that you were right in your analysis if this does not happen.

Yes a dam line of 528 or below is required to see snow, just one of the ingredients. I won't be turning up my nose at anything below it.

Kermit.de.frog · 12-01-2018 11:41pm

Gaoth Laidir · 12-01-2018 11:42pm

nacho libre wrote: »

You don't need 516 to get snow here, of course the lower the thickness the better, i have often seen snow in sub 528 dam thickness

Shedbebreezy wrote: »

Yes a dam line of 528 or below is required to see snow, just one of the ingredients. I won't be turning up my nose at anything below it.

528 will not cut it in a convective setup. 516 guarantees snow for us in such a case, 520 I would say 50:50. I wouldn't use this thickness in any other case as it becomes unreliable due to the effect of upper warm/moist layers.

More reliable for snow is the 850-1000 thickness, which should be <1290, preferably 1280 metres for snow. The GFS has it 1300-1290 m at its lowest, which is more of a mixed precipitation scenario.

Shedbebreezy · 12-01-2018 11:50pm

Gaoth Laidir wrote: »

528 will not cut it in a convective setup. 516 guarantees snow for us in such a case, 520 I would say 50:50. I wouldn't use this thickness in any other case as it becomes unreliable due to the effect of upper warm/moist layers.

More reliable for snow is the 850-1000 thickness, which should be <1290, preferably 1280 metres for snow. The GFS has it 1300-1290 m at its lowest, which is more of a mixed precipitation scenario.

I've had snow in a convective set up lots of times with that level. I must have imagined it.

Gaoth Laidir · 12-01-2018 11:51pm

nacho libre wrote: »

As i keep saying i'm not expecting a foot of snow courtesy of a blizzard. So if that is your criteria for this then you will of course be right. I think we will get 2- 3 cms of snow at lower levels widely in the north west, i will concede that you were right in your analysis if this does not happen.

Blizzards have been mentioned, but I won't be expecting them either.

But this is not a contest of who's right or wrong. Everyone has an opinion, and is entitled to it, but there are one or two new posters who seem to forget that. I hope the whole country gets pasted so Met Éireann can issue a nationwide RED, but I don't think that will happen either...:pac:

Gaoth Laidir · 12-01-2018 11:52pm

Shedbebreezy wrote: »

I've had snow in a convective set up lots of times with that level. I must have imagined it.

When was that, and where?

nacho libre · 12-01-2018 11:52pm

Gaoth Laidir wrote: »

528 will not cut it in a convective setup. 516 guarantees snow for us in such a case, 520 I would say 50:50. I wouldn't use this thickness in any other case as it becomes unreliable due to the effect of upper warm/moist layers.

.

I will respectfully have to disagree. Sub 528 thickness in past north westerly and northerly airflows has delivered snow for my area. I often recall having snow with 525- 520 dam thickness. I am not expecting powdery snow anyway. Wet snow will do fine. Given the dew points it should start accumulating monday night- the caveat being provided charts are not downgraded.

nacho libre · 12-01-2018 11:54pm

Gaoth Laidir wrote: »

Blizzards have been mentioned, but I won't be expecting them either.

But this is not a contest of who's right or wrong. Everyone has an opinion, and is entitled to it, but there are one or two new posters who seem to forget that. I hope the whole country gets pasted so Met reann can issue a nationwide RED, but I don't think that will happen either...:pac:

Well we can at least agree on that:D

Gaoth Laidir · 12-01-2018 11:55pm

nacho libre wrote: »

I will respectfully have to disagree. Sub 528 thickness in past north westerly and northerly airflows has delivered snow for my area. I often recall having snow with 525- 520 dam thickness. I am not expecting powdery snow anyway. Wet snow will do fine. Given the dew points it should start accumulating monday night- the caveat being provided charts are not downgraded.

If wet snow in the fires of hell does it for you then fair play.

I'm not interested in that rain-turning to sleet-to wet snow-back to rain-can't make up my mind- muck :rolleyes:

JanuarySnowstor · 12-01-2018 11:59pm

Larbre34 wrote: »

I'm afraid Kermits I don't agree with Kermits interpretation of the charts .

MOD Changed the wording of your post

In his selective chart posting, he omitted the upper level temp charts for any of the period under discussion, they never exceed -6C at 850, which would be marginal enough in an E/NE'ly situation, but in an atlantic system with a long fetch - albeit polar maritime - they are basically curtains for snow on all but high ground in the north west and north.

A couple of comments:
1) Snow can fall from zero uppers in an Easterly.
2) I'm old enough to remember snow falling from a Southwesterly here in Cork. Yes a southwesterly and snow falling on the south coast. 1984 I think it was.

In general I think Kermits thread is warranted and probably needs to go amber quite soon.

As always time will tell and humble pie will get swallowed

Kermit.de.frog · 13-01-2018 12:02am

Trough lines will offer some enhancement to the shower activity from Monday night.

SeaBreezes · 13-01-2018 12:06am

Sitting on the south coast and every single chart says rain for us. :-( loving the discussion and the passion on the threads lately. Says a lot about how interested people are in the weather! Thank you to all who post charts and discuss its all education to me. Appreciate ye taking the time to post. Thank you.

Oneiric 3 · 13-01-2018 12:19am

I recall that this particular set up in Feb 2014 brought a day of heavy snow showers here, which did settle leading to a good few cms of relatively 'dry' snow for a time.

Though keeping in mind that this was in Feb, when sea temps and Td's in general tend to be lower than at this point of January. We are never going to get epic amounts of snow from a cold westerly (though Jan '84 would be an exception) but snow can happen under such a set up, though whether it will this time around remains to be seen.

M.T. Cranium · 13-01-2018 12:22am

Right now the interesting feature to watch is a wave of low pressure that the GFS has featured at 12z and 18z moving through the southwest, with implied rain-snow boundary somewhere like Clare to Waterford, and potential for significant accumulations north of that. It may be one of those GFS figments or it may turn out to be a solution that other models will catch onto later (00z runs perhaps?).

For now it's not well enough supported to give it more than a one in four chance, but it would be more than just elevation based snowfalls in passing showers. If it comes about. The model uncertainty is related to a difficult system over eastern U.S. today, that was very poorly forecast by all models as recently as 48-72 hours ago. Getting better resolution on it now, GFS seems to develop this Wednesday feature out of the wave currently moving northeast through West Virginia, or possibly a trailing wave on its cold front. Could all be gone by tomorrow though ...

Kermit.de.frog · 13-01-2018 12:27am

M.T. Cranium wrote: »

Right now the interesting feature to watch is a wave of low pressure that the GFS has featured at 12z and 18z moving through the southwest, with implied rain-snow boundary somewhere like Clare to Waterford, and potential for significant accumulations north of that. It may be one of those GFS figments or it may turn out to be a solution that other models will catch onto later (00z runs perhaps?).

For now it's not well enough supported to give it more than a one in four chance, but it would be more than just elevation based snowfalls in passing showers. If it comes about. The model uncertainty is related to a difficult system over eastern U.S. today, that was very poorly forecast by all models as recently as 48-72 hours ago. Getting better resolution on it now, GFS seems to develop this Wednesday feature out of the wave currently moving northeast through West Virginia, or possibly a trailing wave on its cold front. Could all be gone by tomorrow though ...

The shortwave GFS progs for Wednesday night? ECM and UKMO have it but the timing is inconsistent - There is a 12 - 18 hr difference.

I reckon it could be something, we don't want it deepening too much though.

George Sunsnow · 13-01-2018 12:28am

JanuarySnowstor wrote: »

A couple of comments:
1) Snow can fall from zero uppers in an Easterly.

Only if the air from cloud base to ground is not above zero which won’t be the case next week or any week coming in off the Atlantic
Hence the concerns that GL quite rightly pointed out

Now it will be as interesting as ever to see what trumps what in the journey from Baffin to Ireland but I think coastal western areas wil be mostly out of luck on this one
A direct shot down the eastern Atlantic from the pole closer to Ireland and then returning in on a South westerly would actually be better
But well inland and certainly high ground it’s a yes

Not sure what’s going to happen in Cork but I’d expect some snow there at times as the northwesterly has enough land track en route to drop the rh and dew point

nacho libre · 13-01-2018 12:31am

Gaoth Laidir wrote: »

If wet snow in the fires of hell does it for you then fair play. I'm not interested in that rain-turning to sleet-to wet snow-back to rain-can't make up my mind- muck :rolleyes:

Wet snow will do me fine here Gaoth Laidir:pac:
It will be mostly sleet and snow showers for the first couple of days with modest accumulations. Wednesday is when there may well be a mix of rain, sleet, and wet snow across parts of the country.

giveitholly · 13-01-2018 12:31am

George Sunsnow wrote: »

Only if the air from cloud base to ground is not above zero which won’t be the case next week or any week coming in off the Atlantic
Hence the concerns that GL quite rightly pointed out

Now it will be as interesting as ever to see what trumps what in the journey from Baffin to Ireland but I think coastal western areas wil be mostly out of luck on this one
A direct shot down the eastern Atlantic from the pole closer to Ireland and then returning in on a South westerly would actually be better
But well inland and certainly high ground it’s a yes

Not sure what’s going to happen in Cork but I’d expect some snow there at times as the northwesterly has enough land track en route to drop the rh and dew point

And tipperary?

Oneiric 3 · 13-01-2018 12:34am

Chart from mid-January 1984:

Notice how far east the -10c isotherm was over the north Atlantic. Something that would be inconceivable in today's climate.

fraxinus1 · 13-01-2018 12:36am

nacho libre wrote: »

Prove it. You have turned your back on snow so many times here, i don't blame snow if it now turns its back on you:(

...but seriously you should see a bit of snow this week. I will hopefully be looking on enviously at the snow pictures on here next week.

I don’t have the optimism that you guys have. I get disappointed and admittedly a tad narky when things go belly up! But I’m quietly hopeful next week will deliver. In fact I’m supposed to go to visit my son and family in Dublin on Monday but might leave it until next weekend as I don’t want to miss Donegal getting decent snowfall.

George Sunsnow · 13-01-2018 12:38am

giveitholly wrote: »

And tipperary?

It’s a big county!
Roscrea is further north than some of Wicklow!
Lots of precip is key
From an imby perspective in Wicklow,I’m interested in the shortwave but ONLY if the wind is northwesterly

nacho libre · 13-01-2018 12:40am

George Sunsnow wrote: »

It’s a big county!
Roscrea is further north than some of Wicklow!
Lots of precip is key
From an imby perspective in Wicklow,I’m interested in the shortwave but ONLY if the wind is northwesterly

so now you want a northwesterly wind:p

sryanbruen · 13-01-2018 12:44am

Oneiric 3 wrote: »

I recall that this particular set up in Feb 2014 brought a day of heavy snow showers here, which did settle leading to a good few cms of relatively 'dry' snow for a time.

Though keeping in mind that this was in Feb, when sea temps and Td's in general tend to be lower than at this point of January. We are never going to get epic amounts of snow from a cold westerly (though Jan '84 would be an exception) but snow can happen under such a set up, though whether it will this time around remains to be seen.

Correct it did, that was the only day of 2014 I received any snow. I remember the day well as I was doing PE in school then it started to snow which cancelled it. Here's a picture of Dublin on that day:

Oneiric 3 · 13-01-2018 12:46am

If I get to see some lightning during this spell, then that'll be enough for me. Nothing like a cold and airy starry night seeing big blue flashes lighting up the sky from big showers on the west coast.

George Sunsnow · 13-01-2018 12:47am

nacho libre wrote: »

so now you want a northwesterly wind:p

Absolutely if there’s precip from a shortwave coming up from the south and cold air in place!
Lovely icy dew points coming down off lugnaquilla ,snowmageddon yum yum

typhoony · 13-01-2018 12:49am

Gaoth Laidir wrote: »

If wet snow in the fires of hell does it for you then fair play. I'm not interested in that rain-turning to sleet-to wet snow-back to rain-can't make up my mind- muck :rolleyes:

Possibly but personally watching approaching Cumulonimbus clouds rising up high into the deep blue skies is fascinating, that's not what I would call muck, latest GFS is a slight upgrade so rain will be in the minority for most places it will be hail\sleet and snow. throw in a bit of thunder for good measure and you have an interesting weather week ahead.

Longing · 13-01-2018 12:51am

8'' snow from this set up 3 years ago.

Much similer chart has we have seen today for early next week.

highdef · 13-01-2018 1:05am

Longing wrote: »

8'' snow from this set up 3 years ago.

Much similer chart has we have seen today for early next week.

Where are you located? 8" seems a lot for everywhere except maybe high ground in the north or north west

Greenland Express: Snow showers possible from Monday night

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