Risk of Low Level snow showers in Ulster and W/NW Connaught on Friday Morning/Night

Nqp15hhu · 24-03-2021 10:04pm #1

A short period of colder Polar Maritime air will be in place throughout Friday until Saturday morning. The airmass will be relatively cold.

There are two windows for low level snow: Friday morning 7am-10am and Friday 6pm-9am Saturday. The coldest air will be around Friday evening. The gap in time is due to a warm sector coming across the island on Friday afternoon (early).

This is based on the snow-rain charts on Meteociel and the height of the wet bulb zero line amongst other factors.

_________________________________________________________________

Charts

850hpa:

Warm sector

Colder air flowing back in

Freezing Level:

Needs to be <500 metres for low level snow.

Warm sector: snow limited to extreme mountain tops during this part of the day.

Wet Bulb 0c Level:

Needs to be <300 metres. It is marginal during Friday daylight hours.

Dew Point:

Rain/Snow line:

So, in summarising; there is a risk of low level (close to sea level) snow in any showers in the NW, N and W of the island on Friday morning and the overnight hours. The greatest likelihood is on Friday evening.

Elsewhere, inland areas of the Midlands of ROI may see some snow showers, but the S and SE will most likely be rain below 300 metres based on the charts. Areas on the far NW and W coasts may just see sleet or hailstones.

sean555 · 24-03-2021 10:19pm

Level 2? Orange?

giveitholly · 24-03-2021 10:21pm

sean555 wrote: »

Level 2? Orange?

Level 3,Red

M.T. Cranium · 24-03-2021 10:21pm

Just a heads up, a moderator may change that tag if it isn't an official warning, our policy here is to use operational weather warning tags (even in a few cases where perhaps people didn't generally agree with them). Not to say this won't eventually merit a warning, but that's how we roll. When I say "operational" I mean met.ie rather than UKMO although reference is often made to UKMO alert levels for Northern Ireland. At the moment the met.ie website has no operational warnings in place. That could change at any time. I think it could use a level one alert already but that's not up as of 2120h.

Gaoth Laidir · 24-03-2021 11:46pm

UKMO aviation forecast for Scotland and Northern Ireland for 6 am. Only gives snow on mountains above 1500 ft (450 m).

Valid for 0200-1100 UTC

Met Situation Valid at 0600 UTC
MOD TO STRONG SW UNSTABLE FLOW ACROSS THE REGION.
A FIRST OCCLUSION LIES FROM N6000 E00230 TO N6200 W00130, MOV ENE AT 25KT. A SECOND OCCLUSION LIES FROM GALWAY TO OMAGH, MOV E AT 15KT. A TROUGH LIES FROM N5530 W00830 TO BARRA TO BENBECULA TO N5930 W01000,
AND A WARM FRONT LIES FROM N5630 W01100 TO N5800 W01200, BOTH MOV ENE AT 30KT.

Strong wind warning
ISOL, OCNL SEA COT, MEAN 15-20KT GUST 25-30KT. ISOL, SEA COT IN HVY SHRA OR TSRAGS, MEAN 25KT GUST 35KT.

Freezing Level
GEN 3000FT, BUT 4000FT FAR S.

Weather Conditions

Zone 1

W OF A LINE N5430 W01030 TO ISLAY TO FORT WILLIAM TO N5830 W00530 TO N5930 W00430 TO N6030 W00630, MOV ENE AT 30KT:

GEN 40KM, WITH 3-6/8CUSC 3000FT/6000-8000.
OCNL, FRQ FRONT AND TROUGH, 7KM IN SHRA OR RA, WITH 1-3/8ST 1200FT/1500, 3-6/8CUSC 1500-2000FT/6000-8000 AND 3-6/8AC 8000FT/14000.
ISOL, 3500M IN HVY SHRA OR HVY TSRA, WITH 2-5/8ST 1000FT/1500 AND 7/8CB 1500-2500FT/24000.
ISOL, FRONT AND TROUGH, 3000M IN HVY SHRA OR HVY TSRAGS, WITH 4-7/8ST 700FT/1500, 5-8/8CUSC 1500-2000FT/6000-8000, 5-8/8AC 8000FT/14000, AND EMBD CB 1500FT/24000.
WRNG: HILL FG. MOD ICE AND MOD TURB IN CLD. SEV ICE AND SEV TURB IN CB. TS. OCNL MOD TURB BLW 6000FT. SN MON ABV 1500FT.

Zone 2
E OF ZONE 1, AND NW OF A LINE KILKENNY TO DUNDALK TO DUMFRIES TO PERTH TO INVERNESS TO KIRKWALL TO N5930 E00100, MOV E AT 15KT IN S, AND MOV ENE AT 30KT IN N:

GEN 40KM, WITH 3-6/8CUSC 3000FT/6000.
ISOL, OCNL FRONTS, 7KM IN SHRA, WITH 1-3/8ST 1200FT/1500, 3-5/8CUSC 1500-2500FT/6000-8000 AND 3-5/8AC 8000FT/14000.
ISOL FRONTS, 4000M IN HVY SHRA, WITH 3-5/8ST 1000FT/1500, 3-6/8CUSC 1500-2000FT/6000-8000 AND 3-6/8AC 8000FT/14000.
WRNG: HILL FG. MOD ICE AND MOD TURB IN CLD. ISOL MOD TURB BLW 6000FT. SN MON ABV 1500FT N.

Zone 3
REST OF REGION:
GEN 40KM, WITH 0-4/8CUSC 1500-3500FT/4000-6000.
ISOL, LAN TL 10 Z, 3000M IN BR, WITH 0-5/8ST 300-1000FT/1500.
ISOL, LAN TL 09 Z, 200M IN FG, WITH 6-8/8ST SFC/1000FT.
WRNG: HILL FG. MOD ICE AND MOD TURB IN CLD.

Nqp15hhu · 24-03-2021 11:48pm

I did say that the greatest risk was later in the day...

Gaoth Laidir · 24-03-2021 11:52pm

Nqp15hhu wrote: »

I did say that the greatest risk was later in the day...

Their forecast only stretches to 6 am at the moment. We'll see later updates.

pauldry · 25-03-2021 12:24am

There may be sleet or hail but any snowflakes will be mixed into the showers.

Most people now want a warmer spell coz we know any cold now just is a right mess.

M.T. Cranium · 25-03-2021 2:28am

Thread is quite valid and thanks for posting it, but it should be posted without any premature warning levels added in, that was the only point being made and more of an explanation of what I knew was going to happen when moderators spotted the thread with the orange level alert added. It may well come to pass and I would be quite willing to bet they will have a yellow alert at some point, if not the orange.

We have this procedure for a reason, for one thing, it is not legal to post warnings that are not official warnings and I try to avoid doing this in my own forecasting. The government weather agencies have a prime responsibility for alerting the public, if you ever think they are not living up to that, other channels can be used such as a discussion thread here, or contacting them directly (and good luck with that). You could in theory face legal trouble and your own reputation here will suffer if you over-warn on a regular basis as some "out there" have been doing with elaborate warnings going well beyond guidance (the tabloid press being a prime example).

Another reason for the procedure is that some readers may assume the warning is in place if we add the tag, but at that point it only represents the opinion of one (and perhaps more) weather forum participant, which can lead to problems. On rare occasions we do add a statement saying that a higher level of warning may be justified, sort of jumping the gun a bit on warnings we think may be coming along soon.

Easter weekend also looking quite cold with wintry precip potential there too.

Nqp15hhu · 25-03-2021 9:57am

M.T. Cranium wrote: »

Thread is quite valid and thanks for posting it, but it should be posted without any premature warning levels added in, that was the only point being made and more of an explanation of what I knew was going to happen when moderators spotted the thread with the orange level alert added. It may well come to pass and I would be quite willing to bet they will have a yellow alert at some point, if not the orange.

We have this procedure for a reason, for one thing, it is not legal to post warnings that are not official warnings and I try to avoid doing this in my own forecasting. The government weather agencies have a prime responsibility for alerting the public, if you ever think they are not living up to that, other channels can be used such as a discussion thread here, or contacting them directly (and good luck with that). You could in theory face legal trouble and your own reputation here will suffer if you over-warn on a regular basis as some "out there" have been doing with elaborate warnings going well beyond guidance (the tabloid press being a prime example).

Another reason for the procedure is that some readers may assume the warning is in place if we add the tag, but at that point it only represents the opinion of one (and perhaps more) weather forum participant, which can lead to problems. On rare occasions we do add a statement saying that a higher level of warning may be justified, sort of jumping the gun a bit on warnings we think may be coming along soon.

Easter weekend also looking quite cold with wintry precip potential there too.

That’s fair enough. I assigned the warning level from the point of view that members wouldn’t be expecting it with the mild weather we have had of late.

I also wanted people to know that the mild sector was going to be in place through the middle part of the day and not to become complacent in thinking that the cold was done.

Storm 10 · 25-03-2021 11:13am

Nqp15hhu wrote: »

That’s fair enough. I assigned the warning level from the point of view that members wouldn’t be expecting it with the mild weather we have had of late.

I also wanted people to know that the mild sector was going to be in place through the middle part of the day and not to become complacent in thinking that the cold was done.

Believe me they would be expecting it, I doubt there is anyone on here who does not wait for the smallest hint of cold weather warm weather or a storm.

[Deleted User] · 25-03-2021 11:16am

So we are getting the cold for Easter, as expected. Great.

pauldry · 25-03-2021 12:08pm

It will be an interesting day tomorrow anyways so we might as well have a dedicated thread for it. They mentioned a potential yellow level wind event for Saturday too so March going out with a bang after the quiet weather of late.

Yes Easter cold and potentially first half of April

Rossvet · 25-03-2021 12:14pm

CONNACHT!!!!!!

sunbabe08 · 25-03-2021 1:02pm

nothing for cork city? so i don't get my hopes up for nothing

US2 · 25-03-2021 1:08pm

I'm liking a good cold spell in April, means when we do get a settled spell the temperatures will be decent.

Nqp15hhu · 25-03-2021 1:09pm

US2 wrote: »

I'm liking a good cold spell in April, means when we do get a settled spell the temperatures will be decent.

Yeah I prefer the cool and disruptive weather now. Nearly every year that we receive warm, anticyclonic weather in Spring we're left with a wet and abysmal summer.

Chris_5339762 · 25-03-2021 1:15pm

Not a hope in Cork with this, Arpege is forecasting 3-4c early in the morning and 9c on Friday for us, Met.ie 2-3 degrees getting up to about 7.

Nqp15hhu · 25-03-2021 1:27pm

Chris_5339762 wrote: »

Not a hope in Cork with this, Arpege is forecasting 3-4c early in the morning and 9c on Friday for us, Met.ie 2-3 degrees getting up to about 7.

I wouldn't follow Arpege, it seems to be overly warm compared with the other models in most cases. With 850 hPa of -6c, I can't see the freezing level being 900 metres somehow.

Nqp15hhu · 25-03-2021 1:39pm

ECM shows freezing levels of 300 metres or less in Ulster tomorrow evening, but Arpege says 700m. Lol!!

pauldry · 25-03-2021 2:18pm

Looks slightly less cold than before to my untrained eye. A slight shift North on latest GFS. Ulster could still get some sleet and possible snow tomorrow night but the rest of us unlikely.

Nqp15hhu · 25-03-2021 2:19pm

Met Office now has light snow showers tomorrow night.

KanyeSouthEast · 25-03-2021 2:27pm

Nqp15hhu wrote: »

Yeah I prefer the cool and disruptive weather now. Nearly every year that we receive warm, anticyclonic weather in Spring we're left with a wet and abysmal summer.

Or we’ll get cold and disruptive weather now and still get our usual wet and abysmal summer.

US2 · 25-03-2021 2:54pm

KanyeSouthEast wrote: »

Or we’ll get cold and disruptive weather now and still get our usual wet and abysmal summer.

Last two really bad springs i can remember are 13 and 18, both had the nicest summers i can remember

pauldry · 25-03-2021 2:57pm

Yes but this Spring hasnt been all bad and even the cold weather will include portions of dry weather in it.

Cant be as cold as last Summer in Leinster but CAN be in Connaught. In Sligo we did OK last Summer. Dry until June 26th and 2 good weeks in August. July was wintry though.

Oh meant to be talking about tomorrow night. As my best hope is we get those whitening hailstones so kids can fire bits off roof of car at each other.

highdef · 25-03-2021 9:08pm

Any updates on this event? No posts in over 6 hours and the event is scheduled to begin in about 11 hours, tis very strange.

Gaoth Laidir · 25-03-2021 9:33pm

UKMO Ballooning forecast for the Eniskillen area tomorrow morning.

Air temperatures: PS02 means +2, MS01 means -1, etc.

Area Forecast: NORTH
Forecast period: 26 MARCH 2021 0500-1000 UTC
Regional Summary
A cold front crosses the region through the morning bringing widespread showers of rain, some of them heavy with a risk of hail, and snow to higher ground. Behind the cold front further showers will feed in from the west bringing further rain and sleet (or snow to higher ground) and a risk of hail and thunderstorms where showers are heavier. Cloud will be scattered or broken, though overcast in the front, cumulus or stratocumulus (bases 1500-3000ft) and isolated stratus (bases 500-1200ft), with a risk of cumulonimbus, potentially embedded in the front. Winds will be strong southerly ahead of the front and moderate to strong west to south-westerly behind the front, though remaining gusty.
Sea Breeze: Nil

Inversions Min/Max (ft)
Isolated surface inversion to 300ft until 0800 UTC

Outlook for period:3 HOUR PERIOD TO DUSK, 26 MARCH 2021:
Showers, with an increasing likelihood of wintry precipitation, continue to cross the region from the west with a risk of hail and thunderstorms. Winds will be gusty moderate to strong west to south-westerlies.

Nqp15hhu · 25-03-2021 9:45pm

Again not the evening forecast.. the Irish Met Office even allude to snow tomorrow evening.

Gaoth Laidir · 25-03-2021 9:51pm

PM forecast.

Neddyusa · 26-03-2021 12:42am

pauldry wrote: »

It will be an interesting day tomorrow anyways so we might as well have a dedicated thread for it. They mentioned a potential yellow level wind event for Saturday too so March going out with a bang after the quiet weather of late.

Yes Easter cold and potentially first half of April

"March In like a Lamb - Out like a Lion"

The most reliable of all the weather lore sayings in my experience.

mcburns07 · 26-03-2021 1:24am

Neddyusa wrote: »

"March In like a Lamb - Out like a Lion"

The most reliable of all the weather lore sayings in my experience.

The bar is low

Risk of Low Level snow showers in Ulster and W/NW Connaught on Friday Morning/Night

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