Much colder, wintry showers, some of snow Easter Sunday 2021 onward

Gaoth Laidir · 02-04-2021 6:36pm

Nqp15hhu wrote: »

I am not seeing a cap in this sounding:

It's right there, slight at 750 but strong at 650 hPa.

500 hPa temperature there only -25. Over the UK it will be -40, much more conducive for deep convection. We need >42 degrees between the surface and 500 hPa for polar lows to form.

Nqp15hhu · 02-04-2021 6:41pm

In February there was a rapid rise at 800mb and above, I still managed to get some snow showers. This is not the same.

Polar Lows only create warm sectors, they can stay away.

Gaoth Laidir · 02-04-2021 6:43pm

Nqp15hhu wrote: »

In February there was a rapid rise at 800mb and above. This is not the same.

Polar Lows only create warm sectors they can stay away.

Correct, it was much shallower back then. All I'm saying is that the -40 °C 500 hPa cold pool showing in runs earlier in the week has shifted well to the east, and with it the heaviest showers (and hence coldest downdrafts).

Gaoth Laidir · 02-04-2021 6:51pm

Nqp15hhu wrote: »

In February there was a rapid rise at 800mb and above, I still managed to get some snow showers. This is not the same.

Polar Lows only create warm sectors, they can stay away.

Tell that to a Norwegian fishing vessel caught in the middle of one. They're potent little feckers, with whiteout conditions in many.

Nqp15hhu · 02-04-2021 6:55pm

Lows almost always bring a warm sector down in through Donegal and Islay.

As I said no thanks.

Gaoth Laidir · 02-04-2021 7:00pm

Nqp15hhu wrote: »

Lows almost always bring a warm sector down in through Donegal and Islay.

As I said no thanks.

I'm talking about a proper Polar Low.

http://eumetrain.org/resources.html?page=1&cgry=-1&thm=Polar+Low&ctry=-1&months=-1&years=-1&author=-1&sat=-1&instr=-1&prod=-1&level=-1&recent=false&sorter=-1

Nqp15hhu · 02-04-2021 7:06pm

Yes it would warm and mix out the colder air.

JanuarySnowstor · 02-04-2021 8:02pm

Nqp15hhu wrote: »

Yes it would warm and mix out the colder air.[/QUOTE

The older folk on here know what a true polar low means.
They don't have a warm sector but a true polar low hasnt been seen for possibly 30 + years

snowstorm445 · 02-04-2021 8:27pm

It was 26C here in Brussels mid-week and it looks like it'll be subzero with snow overnight on Monday and Tuesday. Feels more like the middle of Russia or Canada with such a huge temperature variation.

Nqp15hhu · 02-04-2021 8:44pm

JanuarySnowstor wrote: »

Nqp15hhu wrote: »

Yes it would warm and mix out the colder air.[/QUOTE

The older folk on here know what a true polar low means.
They don't have a warm sector but a true polar low hasnt been seen for possibly 30 + years

I have a Meteorology bachelors degree. I am quite aware as to what a Polar Low is as well.

“ A Polar Low is a meso-scale cyclone with a warm core only existing in a cold airmass at quite a distance from the polar front. ”

https://rammb.cira.colostate.edu/wmovl/vrl/tutorials/satmanu-eumetsat/satmanu/cms/pl/backgr.htm

Tyrone212 · 02-04-2021 9:01pm

Gaoth Laidir wrote: »

The ECM and ICON were showing that eastern focus yesterday so the GFS is now picking up on it too.

Note too that 850 hPa will be around 200 m higher than it was back in the February event, so the same actual altitude amsl on Monday will be around 2 degrees warmer than at 850 hPa (-7 or -8)

I see. I never looked at the charts until today. Was just reading in here and xcweather for a quick breakdown.

pauldry · 02-04-2021 9:51pm

Another non event.

What a surprise.

Oscar Bravo · 02-04-2021 9:59pm

Massive downgrade on the Rte weather at half 9. Joanna back tracking alot on recent forecasts.

Donegal Storm · 02-04-2021 10:25pm

We haven't had a 'toppler' in years but back in the days where they were a relatively common feature they'd always get shunted east closer to the event. Looks like the same is happening this time

Little snowy old me · 02-04-2021 11:02pm

Ah well. Who wants all that cold weather in April anyway? As much as I love snow, I want it between November and the end of February. Yet more backtracking by many....

Right, as this has been downgraded, that's me done on here until later this year, unless something mega dramatic weather wise kicks off between now and then... which being Ireland, is not likely.

Adios.

Nqp15hhu · 02-04-2021 11:03pm

I know the pressure is high and it may be grasping at straws, but ICON does show quite a few snow showers for northern and north western parts.

There is a slight SW push of cold air on Tuesday.

Nqp15hhu · 02-04-2021 11:07pm

Little snowy old me wrote: »

Ah well. Who wants all that cold weather in April anyway? As much as I love snow, I want it between November and the end of February. Yet more backtracking by many....

Right, as this has been downgraded, that's me done on here until later this year, unless something mega dramatic weather wise kicks off between now and then... which being Ireland, is not likely.

Adios.

The 850 hpa temps have not been downgraded so don't be giving up hope yet.:) I think we could still get snow showers.

And i'm still questioning this sudden change at the last moment, it will be now casting. I will be watching the satellite image to see what way things are moving. Remember initially it was supposed to be mid Atlantic.

km79 · 02-04-2021 11:08pm

Oscar Bravo wrote: »

Massive downgrade on the Rte weather at half 9. Joanna back tracking alot on recent forecasts.

Good

Nqp15hhu · 02-04-2021 11:37pm

Anyway, few seem to care anymore. The cold spell is still on it's way, however, as GL alluded to the upper levels beyond the 850hPa level have warmed up; this does not affect precipitation type or surface temps.

GFS 18z:

The colder air takes a little while to flow in, 10pm, sharp temp gradient still there but not as extreme:

4am:

8am, large gradient across the island, -12c in Ulster, 1c in SW Cork:

5pm Monday:

5pm Tuesday:

Sorry to be the bearer of bad news, but yes the cold spell has downgraded in intensity. It is still coming but the cold air at the surface will be restricted to Ulster with southern areas having highs as much as 7-8c, in sunshine.

Ulster does appear to have a risk of some light, potentially moderate snow showers despite the higher air pressure. This may just be graupel as in the Easterly, it's difficult to know at this stage. Highs here are predicted to be 2-4c on Monday and Tuesday.

This could all revert back tomorrow, though the risk is low sadly.

Kunta Kinte · 02-04-2021 11:38pm

Little snowy old me wrote: »

Ah well. Who wants all that cold weather in April anyway? As much as I love snow, I want it between November and the end of February. Yet more backtracking by many....

Right, as this has been downgraded, that's me done on here until later this year, unless something mega dramatic weather wise kicks off between now and then... which being Ireland, is not likely.

Adios.

Be careful out there.

Cluedo Monopoly · 02-04-2021 11:39pm

Will there be decent snow on high ground (Connemara >500m)?

Nqp15hhu · 02-04-2021 11:41pm

Cluedo Monopoly wrote: »

Will there be decent snow on high ground (Connemara >500m)?

Sorry, but probably not. It'll most likely be sunny there. Maybe a few graupel showers, the issue is not with the temperatures but the air pressure.

SouthWesterly · 02-04-2021 11:44pm

Little snowy old me wrote: »

Ah well. Who wants all that cold weather in April anyway? As much as I love snow, I want it between November and the end of February. Yet more backtracking by many....

Right, as this has been downgraded, that's me done on here until later this year, unless something mega dramatic weather wise kicks off between now and then... which being Ireland, is not likely.

Adios.

Downgrade. Great news. On with the gardening

Meteorite58 · 02-04-2021 11:46pm

Intensity and frequency of showers look less then previously shown for Sunday night into Monday. Monday probably more showers in the Northern half and mostly in Northern coastal counties, wintry and as has been said more in the way of shallow convection, still could get a few hail showers, looking like a low risk of thunderstorm activity. Should be good bright spells the further S on Monday. Fresh and blustery winds later Sunday into Monday, strong on Northern coasts for a time, Monday fresh winds moving down from the N giving a pronounced Windchill.

Monday - Tuesday look like having more of a chance of wintry precipitation in Northern counties, perhaps snow possible but small amounts on lower levels if any I would have thought, mostly hill and Mountains.

Nqp15hhu · 02-04-2021 11:47pm

Meteorite58 wrote: »

Intensity and frequency of showers look less then previously shown for Sunday night into Monday. Monday probably more showers in the Northern half and mostly in Northern coastal counties, wintry and as has been said more shallow convection. Should be good bright spells the further S on Monday. Fresh and blustery winds later Sunday into Monday, strong on Northern coasts for a time, Monday fresh winds moving down from the N giving a pronounced Windchill.

Monday - Tuesday look like having more of a chance of wintry precipitation in Northern counties, perhaps snow possible but small amounts on lower levels if any I would have thought, mostly hill and Mountains.

Do you think this will be like the easterly with mostly light graupel showers, or could we have something more substantial (in terms of shower intensity?)?

Meteorite58 · 03-04-2021 12:10am

Nqp15hhu wrote: »

Do you think this will be like the easterly with mostly light graupel showers, or could we have something more substantial (in terms of shower intensity?)?

Not sure really. Maybe something like starting off with some rain / sleet, some light snow flurries early Monday morning and if there is a source for precipitation then could turn more wintry with more snow flurries during Monday and the models seem to be showing this. Probably a few light hail showers possible during Monday, just my layman's opinion mind you.

The models have eased off on the amount of precipitation, a lot of the weather heading more East as can be seen in the Fax chart as the HP out west muscles in. But as ever lots of unknowns and will be interesting to see the charts tomorrow and Sunday and then watching the data and reports coming in.

03-04-2021 7:59am

Matty (I think) on radio one there
Highs of 12 to 14 on tuesday
I'll take that

Wintry showers on mountains in west munster and north connaught monday
No mention of ulster

OldRio · 03-04-2021 9:41am

SouthWesterly wrote: »

Downgrade. Great news. On with the gardening

Exactly. Wonderful.

Nqp15hhu · 03-04-2021 9:44am

AuntySnow wrote: »

Matty (I think) on radio one there
Highs of 12 to 14 on tuesday
I'll take that
Wintry showers on mountains in west munster and north connaught monday
No mention of ulster

Not a chance.

Nqp15hhu · 03-04-2021 10:49am

The cold air is still on it's way and is still as potent as initially forecast. I am using the 6Z ICON.

Freezing levels are low on Monday, about 300-400 metres in Ulster:

Very low Dew Points:

Max of 3-4c over Ulster:

Periodic snow showers, though look very light at times, sadly:

More snow on Monday night:

Tuesday warms up, freezing levels around 500 metres:

Icon has an undercutting low come through:

This has been forecasted on a few runs of ICON now.

highdef · 03-04-2021 11:00am

Why have you suddenly switched from the GFS here? Does the ICON show you more in line what conditions you want to experience compared to the backtracking GFS?

Nqp15hhu · 03-04-2021 11:01am

No the ICON provides more detail the gfs 6z has the exact same freezing levels.

In fact the gfs has lower 850 temps.

highdef · 03-04-2021 11:03am

Nqp15hhu wrote: »

No the icon provides more detail the gfs has the exact same freezing levels.

In fact the gfs has lower 850 temps.

Ah ok, and thank you for the update about the GFS upgrade this morning.

highdef · 03-04-2021 11:07am

Any chance you can post some air pressure charts from the ICON here? I'm curious to see if the high values forecast by the GFS are also forecast by ICON, in which case we can say goodbye to much, if any in the way of precipitation. GFS has the 1028 mb contour aligned pretty much in the centre of the country, in a North/South axis on Monday. I wouldn't expect anything of note with pressure that high.

Nqp15hhu · 03-04-2021 11:08am

No there hasn’t been an upgrade. Things are very much as they were yesterday.

Gonzo · 03-04-2021 12:42pm

This upcoming cold spell looks dry for the most part, will be a non event for many of us apart from the cold. Not expecting much if anything here in Meath. Northerlies rarely deliver for much of Ireland and this one will be no different than the many 'dry' northerlies or topplers we've had over the past 10 years.

Cluedo Monopoly · 03-04-2021 12:54pm

I will take dry and cold. Great for exercise.

JanuarySnowstor · 03-04-2021 1:51pm

It's funny cause it's downgraded on almost every run over the last 3 days. It's gone from very cold and wintry to dry and cool almost pleasant in sunshine.
Nobody's fault of course other than unreliable models.
They really are useless beyond about 5 days and what I find extraordinary is over 30 years it's hard to see an improvement in how they predict the weather!

Nqp15hhu · 03-04-2021 2:39pm

I have a forecast high of 3/4c on Monday, that’s pretty cold for April.

Nqp15hhu · 03-04-2021 5:06pm

Good news, the 12z is about 20-30 miles west.

Gaoth Laidir · 03-04-2021 9:36pm

Big difference in the latest (18Z) soundings from up to our north. A huge gradient in 850-hPa temperatures, with a 20-degree difference between Keflavik and Jan Mayan, a distance of just 975 km.

Nqp15hhu · 03-04-2021 9:39pm

Yes I imagine the front will bring a sharp gradient. Though the GFS seems to show two fronts? One at 9pm and another at 2am?

nacho libre · 03-04-2021 9:45pm

Nqp15hhu wrote: »

Good news, the 12z is about 20-30 miles west.

It looks mainly dry for most. It was looking good up until a couple of days ago for this northerly to give widespread heavy wintry showers. Northerlies in the past, which were often only two to three day events(topplers) have delivered quite widely across Ireland.

Nqp15hhu · 03-04-2021 9:49pm

nacho libre wrote: »

It looks mainly dry for most. It was looking good up until a couple of days ago for this northerly to give widespread heavy wintry showers. Northerlies in the past, which were often only two to three day events(topplers) have delivered quite widely across Ireland.

I still think we will see light snow showers here with the daytime convection. I’ll be watching the 18z to see if there is another westward shift.

I’ve seen the models move a system east only to move it west at the last moment, in the past.

Nqp15hhu · 03-04-2021 9:58pm

Is this the front north of Iceland? Or is it behind the larger cloud bank/Warm Conveyor belt?

Gaoth Laidir · 03-04-2021 10:12pm

Nqp15hhu wrote: »

Is this the front north of Iceland? Or is it behind the larger cloud bank/Warm Conveyor belt?

The front is just stradling the north of Iceland this evening and is moving southwards. That feature you highlighted is just a decaying occlusion and won't be a feature.

The image below shows the ECMWF thickness (green) and Thermal Front Parameter (blue), both of which can be used to locate the front.

http://212.232.25.232/ng-maps/

M.T. Cranium · 04-04-2021 12:04am

Sharp temperature gradient across Iceland with this front, as shown on map ... and -10 at Jan Mayen Island to the northeast of Iceland.

https://www.meteociel.fr/observations-meteo/temperatures.php?region=is

(this map may update for later readers, when I saw it the temperature was 10 C on the eastern tip of Iceland and -7 on the northeast coast, wind shift from SW to NNE. Some differences in observation time should be noted also)

Kermit.de.frog · 04-04-2021 12:09am

Thank god I couched the thread title in just enough ambiguity :pac:

Not as impactful as it might have been but a few wintry showers mainly in the north and west, some of snow. Frosty nights to come too.

Nqp15hhu · 04-04-2021 12:15am

M.T. Cranium wrote: »

Sharp temperature gradient across Iceland with this front, as shown on map ... and -10 at Jan Mayen Island to the northeast of Iceland.

https://www.meteociel.fr/observations-meteo/temperatures.php?region=is

(this map may update for later readers, when I saw it the temperature was 10 C on the eastern tip of Iceland and -7 on the northeast coast, wind shift from SW to NNE. Some differences in observation time should be noted also)

What’s your verdict on snow showers?

M.T. Cranium · 04-04-2021 12:33am

Some scattered 1-2 cm falls but as people are saying, a rather dry look to this, the uppers look promising though. The second wave of colder air around Friday-Saturday may do better for snow showers as there's less influence of high pressure in that case.

Would expect snow pellets to be the precip of choice given the dynamics. Same look out the window but a different result on the ground (drifts of them fairly easy to create in a breeze).

Thunder seems possible too given the lapse rates likely over the 7-9 C ocean surfaces.

Much colder, wintry showers, some of snow Easter Sunday 2021 onward

Comments