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

highdef

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

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

In fact the gfs has lower 850 temps.

highdef

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

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

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

Gonzo

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

I will take dry and cold. Great for exercise.

JanuarySnowstor

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

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

Nqp15hhu

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

Gaoth Laidir

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

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

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

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

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

Gaoth Laidir

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

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

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

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

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.

Nqp15hhu

M.T. Cranium wrote: »

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.

So for my location would it mostly be sunny or passing light showers?

It’s interesting you talk about precipitation choice. We alternate between hail/graupel and snow here... I have had northerlys in the past that were all hail despite the cold temps. What determines the form of frozen precipitation?

Birdnuts

The severity of the air frosts next week appears to be the main issue - looks like alot of damage could be done to spring foliage over the coming days:(

M.T. Cranium

Could only give a general estimate of 30 per cent coverage for snow showers, so partly not knowing exactly your location I would be guessing entirely, if you don't get snow at your exact location then within 10-20 miles probably.

These different forms of frozen precip all depend on height of formation and rate of fall, which gives some idea of time of exposure to temperatures once they head towards the ground. GL probably knows more technical detail, I tend more towards pattern recognition. We had a day here recently with several snow pellet showers and from what I recall the atmosphere was in almost the same condition as we're expecting to see over Ireland on Monday.

Nqp15hhu

So, the cold spell is dead set now. It's coming. Let's look at the showery activity. Most of the snow will be in Ulster.

ICON:

Monday looks to have light snow showers, starting sunny and becoming more frequent towards the evening as lower heights move SW:




By midnight the shower activity picks up significantly, evening making it as far south as Belfast:



Tuesday is also showery:



Arpege:

Arpege Monday, a few showers:


Arpege also shows this uptake tomorrow night:




HIRLAM:





WRF:






So, interestingly despite the high pressure and heights, all models actually show snow showers. Irritatingly it'll be one of those annoying days with a high max in the early hours that does not represent the temps throughout the day. Hopefully the temp here is below 5c by midnight.

up for anything

Ah FFS! It's my birthday tomorrow. Should I cancel the outdoor picnic? :(:(

Nqp15hhu

M.T. Cranium wrote: »

Could only give a general estimate of 30 per cent coverage for snow showers, so partly not knowing exactly your location I would be guessing entirely, if you don't get snow at your exact location then within 10-20 miles probably.

These different forms of frozen precip all depend on height of formation and rate of fall, which gives some idea of time of exposure to temperatures once they head towards the ground. GL probably knows more technical detail, I tend more towards pattern recognition. We had a day here recently with several snow pellet showers and from what I recall the atmosphere was in almost the same condition as we're expecting to see over Ireland on Monday.

I live to the NE of the Limavady area, i'm not saying exactly where as I have creepers from reddit stalking me.

I'm just curious to see if there was a way for me to identify what type of frozen precipitation falls. All material I read references a warmer layer, but in most situations with the graupel there is no warm layer looking at the sounding.

I have seen graupel at high elevations that remained below freezing.

Nqp15hhu

up for anything wrote: »

Ah FFS! It's my birthday tomorrow. Should I cancel the outdoor picnic? :(:(

No, most of the south will be sunny with tepid temps. Potentially you could see a light graupel shower at best.

RocketRaccoon

It's hard to believe there is cold weather coming. I'm sunburnt from working in the garden yesterday and the sun is splitting the rocks again today here in Clare.

RocketRaccoon

RocketRaccoon wrote: »

It's hard to believe there is cold weather coming. I'm sunburnt from working in the garden yesterday and the sun is splitting the rocks again today here in Clare.

Living in the Banner like yourself, also been digging, composting and planting recently. This cold spell is a major headache, moved the pots en masse into the shed this morning as a precaution. An arctic blast is utterly useless this time of year, sun too powerful for any snow to stick long. Every downgrade heartily welcome, winter can kindly frig off until November.

pad199207

[Deleted User] wrote: »

Living in the Banner like yourself, also been digging, composting and planting recently. This cold spell is a major headache, moved the pots en masse into the shed this morning as a precaution. An arctic blast is utterly useless this time of year, sun too powerful for any snow to stick long. Every downgrade heartily welcome, winter can kindly frig off until November.

Indeed and thankfully downgrades have happened leading up to this. It looks to be a mainly dry chilly snap too which also helps with the gardens. Cold and Wet would be significantly worse.