The Weather Outlook

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Quantum
  • Quantum
  • Advanced Member Topic Starter
01 March 2024 09:19:21
Front looking more active than expected, this should increase the snow risk.
25/26 (850hpa temp) 11 days snow/sleet falling

18/11 (-4) 19/11 (-6) 20/11 (-6) 01/01 (-7) 04/01 (-10) 10/01 (-7) 11/01 (-3) 30/01 (-1) 13/02 (-6) 15/02 (-4) 18/02 (-6)

24/25 10d

18/11 (-6) 19/11 (-6) 23/11 (-2) 22/12 (-5) 04/01 (-5) 05/01 (0)14/02 (0) 15/02 (0)12/03 (-6) 13/03 (-6)

23/24 8d

29/11 (-6) 30/11 (-6) 02/12 (-5) 03/12 (-5) 04/12 (-3) 16/01 (-3) 18/01 (-8)08/02 (-5)

22/23 7d

18/12 (-1)06/03 (-6) 08/03 (-8) 09/03 (-6) 10/03 (-8) 11/03 (-5) 14/03 (-6)

21/22 12d

Chunky Pea
01 March 2024 09:27:20

My rough estimate at the snow risk tommorow to lower levels. Most of the snow will be from the heavy showers behind the front, not the front itself. Devon and the South west are at high risk in particular which makes this an odd map to draw.

https://snipboard.io/4L3M8z.jpg 

UserPostedImage

Originally Posted by: Quantum 

I was in Q's 60 % range, and those in the 80% range are seeing the snow settle. Good call for Ireland at least

Patrick,

East Galway, Ireland.

Quantum
  • Quantum
  • Advanced Member Topic Starter
01 March 2024 10:05:46
The short term maps always seem to get a good reception so might do one for tommorow later which I don't expect to be much easier. Evap cooling dominated events seldom are.
25/26 (850hpa temp) 11 days snow/sleet falling

18/11 (-4) 19/11 (-6) 20/11 (-6) 01/01 (-7) 04/01 (-10) 10/01 (-7) 11/01 (-3) 30/01 (-1) 13/02 (-6) 15/02 (-4) 18/02 (-6)

24/25 10d

18/11 (-6) 19/11 (-6) 23/11 (-2) 22/12 (-5) 04/01 (-5) 05/01 (0)14/02 (0) 15/02 (0)12/03 (-6) 13/03 (-6)

23/24 8d

29/11 (-6) 30/11 (-6) 02/12 (-5) 03/12 (-5) 04/12 (-3) 16/01 (-3) 18/01 (-8)08/02 (-5)

22/23 7d

18/12 (-1)06/03 (-6) 08/03 (-8) 09/03 (-6) 10/03 (-8) 11/03 (-5) 14/03 (-6)

21/22 12d

+1
Saint Snow
01 March 2024 10:10:24

My rough estimate at the snow risk tommorow to lower levels. Most of the snow will be from the heavy showers behind the front, not the front itself. Devon and the South west are at high risk in particular which makes this an odd map to draw.

https://snipboard.io/4L3M8z.jpg 

UserPostedImage

Originally Posted by: Quantum 

I'm on the boundary of the 40% and 60%. 

Plenty of rain so far but no snow.

Edit - the Pennine M62 no snow. Flash Bar Store and Cat & Fiddle both got lying snow (https://www.maccinfo.com/Flash/ )

Martin

Home: St Helens (26m asl) Work: Manchester (75m asl)

A TWO addict since 14/12/01

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Aneurin Bevan

Chunky Pea
01 March 2024 10:21:36

I'm on the boundary of the 40% and 60%. 

Plenty of rain so far but no snow.

Edit - the Pennine M62 no snow. Flash Bar Store and Cat & Fiddle both got lying snow (https://www.maccinfo.com/Flash/ )

Originally Posted by: Saint Snow 

Coming down pretty thickly here. Not sure where this occluded front is currently positioned but don't rule out a few surprises later for yourself as it swings closer. 

Patrick,

East Galway, Ireland.

Quantum
  • Quantum
  • Advanced Member Topic Starter
01 March 2024 10:25:11

I'm on the boundary of the 40% and 60%. 

Plenty of rain so far but no snow.

Edit - the Pennine M62 no snow. Flash Bar Store and Cat & Fiddle both got lying snow (https://www.maccinfo.com/Flash/ )

Originally Posted by: Saint Snow 

Tbh I think most of that coin flip is going to be in the showers later rather than the front. Look out for heavy showers later that turn to big sticky flakes when they get heavy enough. Intensity really will be key with marginal freezing levels.

25/26 (850hpa temp) 11 days snow/sleet falling

18/11 (-4) 19/11 (-6) 20/11 (-6) 01/01 (-7) 04/01 (-10) 10/01 (-7) 11/01 (-3) 30/01 (-1) 13/02 (-6) 15/02 (-4) 18/02 (-6)

24/25 10d

18/11 (-6) 19/11 (-6) 23/11 (-2) 22/12 (-5) 04/01 (-5) 05/01 (0)14/02 (0) 15/02 (0)12/03 (-6) 13/03 (-6)

23/24 8d

29/11 (-6) 30/11 (-6) 02/12 (-5) 03/12 (-5) 04/12 (-3) 16/01 (-3) 18/01 (-8)08/02 (-5)

22/23 7d

18/12 (-1)06/03 (-6) 08/03 (-8) 09/03 (-6) 10/03 (-8) 11/03 (-5) 14/03 (-6)

21/22 12d

Russwirral
01 March 2024 10:26:18

The short term maps always seem to get a good reception so might do one for tommorow later which I don't expect to be much easier. Evap cooling dominated events seldom are.

Originally Posted by: Quantum 

Q - am I right in thinking our proximity to the center of the Low, will also be a factor? as in temperatures required and DPs?

Weather station:

https://www.wunderground.com/personal-weather-station/dashboard?ID=IWIRRAL24#history 

Quantum
  • Quantum
  • Advanced Member Topic Starter
01 March 2024 10:32:18

Q - am I right in thinking our proximity to the center of the Low, will also be a factor? as in temperatures required and DPs?

Originally Posted by: Russwirral 

Yes, the closer to the centre the slacker the wind which should increase the effectiveness of evap cooling and bring the temperature down more efficiently. The wind direction also matters. Chunky is seeing snow from the front while saint is not largelly because he is downstream of the evap cooling. Evap cooling is occuring over the entire front and that cold air is being advected westward, so the further west you are, the better you are going to do in this setup.

However for people like Saint, the wind direction is going to change later to become less easterly and more southerly which should increase the risk of snow since it will put him more downstream of the evap cooling effect.

I should add we are fairly lucky the centre of the low has formed over land and not the sea. Occluded LPs generally form something called a 'warm seclusion' which is almost like a warm core characturistic when they spin over open water. That would kill off any snow potential pretty quickly.

 

25/26 (850hpa temp) 11 days snow/sleet falling

18/11 (-4) 19/11 (-6) 20/11 (-6) 01/01 (-7) 04/01 (-10) 10/01 (-7) 11/01 (-3) 30/01 (-1) 13/02 (-6) 15/02 (-4) 18/02 (-6)

24/25 10d

18/11 (-6) 19/11 (-6) 23/11 (-2) 22/12 (-5) 04/01 (-5) 05/01 (0)14/02 (0) 15/02 (0)12/03 (-6) 13/03 (-6)

23/24 8d

29/11 (-6) 30/11 (-6) 02/12 (-5) 03/12 (-5) 04/12 (-3) 16/01 (-3) 18/01 (-8)08/02 (-5)

22/23 7d

18/12 (-1)06/03 (-6) 08/03 (-8) 09/03 (-6) 10/03 (-8) 11/03 (-5) 14/03 (-6)

21/22 12d

Tim A
01 March 2024 10:38:43
Rain here and 3.2c, the front lost its intensity. A few days back it looked like a covering was possible from the band but there have been downgrades in the last 48 hours. 
Tim

NW Leeds

187m asl

 My PWS 

Quantum
  • Quantum
  • Advanced Member Topic Starter
01 March 2024 10:41:20

Rain here and 3.2c, the front lost its intensity. A few days back it looked like a covering was possible from the band but there have been downgrades in the last 48 hours. 

Originally Posted by: Tim A 

You could still get a covering, some of these showers later will be really quite heavy. Get the right shower and you could drop alot of snow pretty quickly. Though I expect this to more apply to places like Bristol than Leeds.

 

25/26 (850hpa temp) 11 days snow/sleet falling

18/11 (-4) 19/11 (-6) 20/11 (-6) 01/01 (-7) 04/01 (-10) 10/01 (-7) 11/01 (-3) 30/01 (-1) 13/02 (-6) 15/02 (-4) 18/02 (-6)

24/25 10d

18/11 (-6) 19/11 (-6) 23/11 (-2) 22/12 (-5) 04/01 (-5) 05/01 (0)14/02 (0) 15/02 (0)12/03 (-6) 13/03 (-6)

23/24 8d

29/11 (-6) 30/11 (-6) 02/12 (-5) 03/12 (-5) 04/12 (-3) 16/01 (-3) 18/01 (-8)08/02 (-5)

22/23 7d

18/12 (-1)06/03 (-6) 08/03 (-8) 09/03 (-6) 10/03 (-8) 11/03 (-5) 14/03 (-6)

21/22 12d

Chunky Pea
01 March 2024 10:43:25

The wind direction also matters. Chunky is seeing snow from the front while saint is not largelly because he is downstream of the evap cooling. 

 

Originally Posted by: Quantum 

For what it is worth, wind direction here is NNW. Wind about 5 knots mean (light), with steady pressure (987mb) 

Patrick,

East Galway, Ireland.

Quantum
  • Quantum
  • Advanced Member Topic Starter
01 March 2024 10:47:37

For what it is worth, wind direction here is NNW. Wind about 5 knots mean (light), with steady pressure (987mb) 

Originally Posted by: Chunky Pea 

https://xcweather.co.uk/

Overall though its  still downstream, I'm guessing you are in the part where it starts to curl back, if you follow the arrows back you can see how far the air has had to travel; even if we assume some warming up over the Irish sea. By contrast in Northern England there is a fairly quick direct route from the north sea.

25/26 (850hpa temp) 11 days snow/sleet falling

18/11 (-4) 19/11 (-6) 20/11 (-6) 01/01 (-7) 04/01 (-10) 10/01 (-7) 11/01 (-3) 30/01 (-1) 13/02 (-6) 15/02 (-4) 18/02 (-6)

24/25 10d

18/11 (-6) 19/11 (-6) 23/11 (-2) 22/12 (-5) 04/01 (-5) 05/01 (0)14/02 (0) 15/02 (0)12/03 (-6) 13/03 (-6)

23/24 8d

29/11 (-6) 30/11 (-6) 02/12 (-5) 03/12 (-5) 04/12 (-3) 16/01 (-3) 18/01 (-8)08/02 (-5)

22/23 7d

18/12 (-1)06/03 (-6) 08/03 (-8) 09/03 (-6) 10/03 (-8) 11/03 (-5) 14/03 (-6)

21/22 12d

+1
Chunky Pea
01 March 2024 11:02:47
Thick snow instantly turned to light rain. Not even a gradual transition. Very messy. sloppy front. 
Patrick,

East Galway, Ireland.

Quantum
  • Quantum
  • Advanced Member Topic Starter
01 March 2024 11:07:02

Thick snow instantly turned to light rain. Not even a gradual transition. Very messy. sloppy front. 

Originally Posted by: Chunky Pea 

Slight change in wind direction may push the cold air elsewhere!

The last snow event (in my sig) went the opposite direction I saw rain to snow within about 15 minutes. Evap cooling events can be downright wierd as you can end up with very local pockets of cold air. For example if there is a very big shower later that generates its own downdraught and then advects that cold air somewhere else it could turn another light shower to snow unexpectedly. Usually this doesn't happen because winds are too strong and blown directly from the sea. However today we have the really quite rare combination of 'cold enough' uppers under a slack low.

When evap cooling is involved it also shows how pointless uppers become; its all about wind speed, direction, and humidity.

EDIT: you'll notice on my map I put literally the entire british isles (except the far SW of Ireland, channel islands, scily and the far SE) under the 20% or above zone. I don't usually do this and its deliberate, I expect basically anywhere could see snow today and it will be very local depending on where these little pockets of cold air are.

 

25/26 (850hpa temp) 11 days snow/sleet falling

18/11 (-4) 19/11 (-6) 20/11 (-6) 01/01 (-7) 04/01 (-10) 10/01 (-7) 11/01 (-3) 30/01 (-1) 13/02 (-6) 15/02 (-4) 18/02 (-6)

24/25 10d

18/11 (-6) 19/11 (-6) 23/11 (-2) 22/12 (-5) 04/01 (-5) 05/01 (0)14/02 (0) 15/02 (0)12/03 (-6) 13/03 (-6)

23/24 8d

29/11 (-6) 30/11 (-6) 02/12 (-5) 03/12 (-5) 04/12 (-3) 16/01 (-3) 18/01 (-8)08/02 (-5)

22/23 7d

18/12 (-1)06/03 (-6) 08/03 (-8) 09/03 (-6) 10/03 (-8) 11/03 (-5) 14/03 (-6)

21/22 12d

+1
Quantum
  • Quantum
  • Advanced Member Topic Starter
01 March 2024 11:08:48
I should add that the showers will not also entirely rely on evap cooling. There is also a 'brute force, so heavy that it literally drags cold air down' element.

 

25/26 (850hpa temp) 11 days snow/sleet falling

18/11 (-4) 19/11 (-6) 20/11 (-6) 01/01 (-7) 04/01 (-10) 10/01 (-7) 11/01 (-3) 30/01 (-1) 13/02 (-6) 15/02 (-4) 18/02 (-6)

24/25 10d

18/11 (-6) 19/11 (-6) 23/11 (-2) 22/12 (-5) 04/01 (-5) 05/01 (0)14/02 (0) 15/02 (0)12/03 (-6) 13/03 (-6)

23/24 8d

29/11 (-6) 30/11 (-6) 02/12 (-5) 03/12 (-5) 04/12 (-3) 16/01 (-3) 18/01 (-8)08/02 (-5)

22/23 7d

18/12 (-1)06/03 (-6) 08/03 (-8) 09/03 (-6) 10/03 (-8) 11/03 (-5) 14/03 (-6)

21/22 12d

Chunky Pea
01 March 2024 11:09:48

Slight change in wind direction may push the cold air elsewhere!

 

Originally Posted by: Quantum 

Spot on. Changed from NNW to NNE. 

Patrick,

East Galway, Ireland.

Quantum
  • Quantum
  • Advanced Member Topic Starter
01 March 2024 11:14:38

Spot on. Changed from NNW to NNE. 

Originally Posted by: Chunky Pea 

Your bubble of cold is on its way to cornwall and devon now.

Its time to look South west for the snow risk. Its not often plymouth and exetor are in the firing line!

 

25/26 (850hpa temp) 11 days snow/sleet falling

18/11 (-4) 19/11 (-6) 20/11 (-6) 01/01 (-7) 04/01 (-10) 10/01 (-7) 11/01 (-3) 30/01 (-1) 13/02 (-6) 15/02 (-4) 18/02 (-6)

24/25 10d

18/11 (-6) 19/11 (-6) 23/11 (-2) 22/12 (-5) 04/01 (-5) 05/01 (0)14/02 (0) 15/02 (0)12/03 (-6) 13/03 (-6)

23/24 8d

29/11 (-6) 30/11 (-6) 02/12 (-5) 03/12 (-5) 04/12 (-3) 16/01 (-3) 18/01 (-8)08/02 (-5)

22/23 7d

18/12 (-1)06/03 (-6) 08/03 (-8) 09/03 (-6) 10/03 (-8) 11/03 (-5) 14/03 (-6)

21/22 12d

+1
Chunky Pea
01 March 2024 11:50:28
Dewpoint trend over the last hour here. Sudden and steady rise upon slight windshift. 

UserPostedImage

Patrick,

East Galway, Ireland.

Crepuscular Ray
01 March 2024 11:50:44
My daughter's team (carers) have had their work cut out this morning in the High Peak. Quite a bit of snow on the roads
Jerry

Edinburgh, in the frost hollow below Blackford Hill

Quantum
  • Quantum
  • Advanced Member Topic Starter
01 March 2024 12:27:54
We can use the radar to estimate where the downstream effects of evap is going to be most effective. I've used the rainfall tendency as a proxy for wind direction in the boundary layer; this is better than surface wind since its more up to date and takes height into account. Anyway you can see that the winds are perpendiculat to the front for most of England so evap cooling is ineficient. BUT the showers in the south west cover large parts of England in cold air downstream. I've highlighted in blue where the greatest potential is.

https://snipboard.io/PBQ5oL.jpg

UserPostedImage 

25/26 (850hpa temp) 11 days snow/sleet falling

18/11 (-4) 19/11 (-6) 20/11 (-6) 01/01 (-7) 04/01 (-10) 10/01 (-7) 11/01 (-3) 30/01 (-1) 13/02 (-6) 15/02 (-4) 18/02 (-6)

24/25 10d

18/11 (-6) 19/11 (-6) 23/11 (-2) 22/12 (-5) 04/01 (-5) 05/01 (0)14/02 (0) 15/02 (0)12/03 (-6) 13/03 (-6)

23/24 8d

29/11 (-6) 30/11 (-6) 02/12 (-5) 03/12 (-5) 04/12 (-3) 16/01 (-3) 18/01 (-8)08/02 (-5)

22/23 7d

18/12 (-1)06/03 (-6) 08/03 (-8) 09/03 (-6) 10/03 (-8) 11/03 (-5) 14/03 (-6)

21/22 12d

scillydave
01 March 2024 12:44:33
Very heavy hail shower here about 10 minutes ago. A real window rattler.
Currently living at roughly 65m asl North of Cowbridge in the Vale of Glamorgan.

Formerly of, Birdlip, highest village in the Cotswolds and snow heaven in winter; Hawkinge in Kent - roof of the South downs and Isles of Scilly, paradise in the UK.

Brian Gaze
01 March 2024 13:36:27
Rain, glorious rain, in the Chilterns. Lots of it too. 
Brian Gaze

Berkhamsted

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overland
01 March 2024 14:08:26

Your bubble of cold is on its way to cornwall and devon now.

Its time to look South west for the snow risk. Its not often plymouth and exetor are in the firing line!

 

Originally Posted by: Quantum 

I hope this equally applies to Swansea! We have had a couple of heavy hail showers, but no snow - yet!

Mumbles, Swansea. 80m asl
Tim A
01 March 2024 14:47:58
We had some wet flakes in the heavier bursts but far off settling snow with the temp above 2.5c at all times.  7mm rain so that would have been a good fall had it been a couple of degrees colder.

Moors look white above 350m to the SW. 

Have to get very lucky from an intense shower to get anything out of this weekend. 

Tim

NW Leeds

187m asl

 My PWS 

ARTzeman
01 March 2024 14:55:52
several falls of hail and rain today. The  latest covering the edges of the lawn.



Some people walk in the rain.

Others just get wet.

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