 Poster: A snowHead
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In the US at least, puking would mean snow only - as in a ton of it in a very short window
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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@BobinCH, it had snowed at ours before 08:00 by which it had turned to rain. It's 1 degree though and looking out the window the LPN (love that) is around 1,400m?
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Okay @under a new name help me out, I know what it is but what does the LPN acronym stand for again? 
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Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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You need to Login to know who's really who.
You need to Login to know who's really who.
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Makes sense, I like it!
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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@coldrainsnow, someone used it above and it resonated. Sorry for being obtuse.
@wjrlaw,
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a ton of it in a very short window
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Not sure the "short window" is mandatory ... as in "it's been pukin' it for two days now and we've run out of beans".
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You'll need to Register first of course.
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No logic to the FL aka LPN, the joys of a temperature inversion from this warm front ?
No change to the temp +1.9 at 1400m when I went to bed, awoke to the same temp but could hear the rain, opened up the blinds at least expecting to see snow on the trees higher up at circa 2,100m, but zero fresh 
Last edited by You'll need to Register first of course. on Fri 1-12-23 9:48; edited 1 time in total
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Just flicked thru the YouTube live links for Verbier village and Les Gets both showing heavy snow.
Meribel appears to be raining still though looking at the trees.
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The line between warm and cold air goes straight through the alps again today .
Last night Meteo Tarentaise claimed rainfall of between 40 and 50mm in the valley around Bourg St Maurice and a LPN that rose as high as 2300m with snowfall of around 50cm above 2800m
He’s looking at LPN at around 2100m today before that drops sharply to 1500m at around 7pm dropping overnight to the valley base sub 800m ….
V cold Sunday -7c in Bourg , It’s like a rollercoaster .
I noted with interest again yesterday Rain above 2000m in Haute Tarentaise whilst just a few km away over the Alpine Ridge heavy snow all day at 1400m in La Thuille and Courmayeur
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You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
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@kitenski, Fascinating isn’t it
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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MeteoAlpes referring to snow in Morzine (1000m) this morning and even 800m in the Vallée Verte a little further northwest. While simultaneously rain to 2,400m+ above Val Thorens. Pretty amazing.
Last edited by snowHeads are a friendly bunch. on Fri 1-12-23 11:58; edited 1 time in total
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And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
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Heavy snow to village level in both Crans Montana and Zermatt this morning, 1500 metresish
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@Rob Mackley, yup
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You know it makes sense.
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@denfinella, is that the line between the cold air/warm air or some other local "cold patch" which has caused that?
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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Been watching the la plagne cams today with interest as we travel 2 weeks today. Lots of melt below 2000m yesterday and today.
The snow line seemed to fluctuate between 1900 and 2500m. Right now it looks like snow down to les coches at 1500m. Let's hope temps keep dropping and snow keeps falling to repair some of the melt.
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Poster: A snowHead
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@kitenski, warm air / cold air boundary (which has moved south now fortunately).
At the time of this morning's post it was colder still a bit further north / east - snowing in Zurich city centre for example.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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Is it just me, as a Scot, who thinks that this is perfect base building conditions? Freeze thaw = much more resilient snow for later.
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Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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@scottishandy, on piste yeah, off piste is a weak layer that'll get buried......
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You need to Login to know who's really who.
You need to Login to know who's really who.
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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Is that skiing or mincing
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You'll need to Register first of course.
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Some fantastically snowy webcam shots from the northern French / Swiss Alps this morning, right down to low levels 
Unusually, some parts of the Italian Alps (e.g. Trentino area) seem to have been much more affected by rainfall since the temperature didn't drop until after the rain had nearly stopped.
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A good 20-25cms at 1,000m in Chamonix on the pool rails this AM, per my pisteur buddy, large amounts above 2,000m ...
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Blast !!! trip planned to Verbier for Monday 11th for a couple of days, Snowforcast saying get warm with rain up to 2000m, tell me its not true, but it is more than a week away so hopefully it might change
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You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
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@Thunderer21, Snowforecast uses (I think) a single run of a single model so is massively volatile at anything over a couple of days. Meteoblue (as recommended on here) uses multiple models so is a better bet.
Pretty sure SF uses the Operational run of GFS (others will know better) and that’s the solid green line on this (top lines are temperature at c1500m and the bottom is precipitation). You can see the Op run has a spike of both temp and precipitation, but the white line (the average of all the model runs) is far less spiky. Anything more than. A week or so out you should be looking at the average not a single run (and even then it’ll be wrong).
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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I love the idea around here that rain is good for the "base". Sure if you never leave a piste, and a ten-ton piste basher regularly squashes the water out and breaks up the resulting sheet ice. Off-piste, rain layers might as well be land mines, they are that dangerous because of the rotten, fragile layer they leave behind. Avalanche people know it as a persistent weak layer:
https://utahavalanchecenter.org/blog/71743
With the amount of snow that we've just had on top of a heavy rain event, people are going to get caught out and pay the price.
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And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
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That looks nasty, and shows just how much precip the mountains have had this week.
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@shannyla, this is why people think rain can help the snowpack. Taken from an avalanche expert's web-page.
"Natural wet snow avalanches that release on steep slopes due to rain and a big increase in temperatures, during and just after snowstorms, can and do cause tragic accidents....
...the net outcome of this warming and especially rain, wherever free water has dripped down through the snowpack, will be a stabilising ‘glueing’ effect, especially when temperatures go down below freezing level again. You may notice that even within 12-24 to 48 hours of this warming episode/rain, the avalanche danger rating will drop by at least one level on the scale."
This, to me, seems to imply that in the short term avalanches can be set off by rain but in the longer term (a week or even less maybe) it actually brings stability once it has all re-frozen. The link you provided talked of persistant weak layers but at no point mentioned rain. In fact you prompted me to search for info and I couldn't find anything suggesting that rain causes persistant weak layers. Only things I could find was that the rain adds a lot of weight and melt to snow and cause slides very quickly during the event and for a couple of days afterwards. Could more knowledgeable people give opinions on what I seem to have found in my reading.
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You know it makes sense.
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@beeryletcher, does the expert then describe what happens when fresh snow falls on top of the refrozen snowpack?
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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@beerylethcer & @shannyla,
My understanding of weak layers in the snow pack is that they're predominantly caused by depth hoar in the Alps, which is formed from amazing looking ice crystalline growth like structures that initially form on the outer layer of the snow. If & when there's a fresh fall of snow on top of this crystalline layer of hoar, this then becomes compressed into a buried layer of ice in the snow pack, which is very fragile & as we know can unfortunately be deadly dangerous if people ski on it without considering it fully in their risk analysis.
AFAIR the fields of ice crystals that make up this depth hoar layer are most often created by humidity & freezing conditions combining to produce them.
What I don't know is if this relatively high humidity required to produce hoar is more likely after rain? It would seem likely that it may be, but i don't know tbh. Perhaps someone else might be able to answer this part ??
P.s . It seems likely that rain should cause higher humidity, which in turn is more likely to result in the conditions for hoar formation, but if I know anything about weather & climate (& tbh I don't know that much) it is that it can confound seeming logic at times. Hope this is of some use nonetheless.
It would be great to hear from someone who is expert & fully up to speed on this to fill in the missing pieces (no pun intended!) 
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Poster: A snowHead
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| Thunderer21 wrote: |
| Blast !!! trip planned to Verbier for Monday 11th for a couple of days, Snowforcast saying get warm with rain up to 2000m, tell me its not true, but it is more than a week away so hopefully it might change |
I would not be worrying about this. Even if it happens most of the good skiing in Verbier is above 2200m and early season conditions are amazing with record breaking levels of snow high up
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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@kitenski, Not really, but seems to me the water mostly works it way down into the snowpack before re-freezing - doesn't sit on the top.
The page link is: https://henrysavalanchetalk.com/rapid-warming-rain-and-wet-snow-avalanches/
Also, as I said before, all my searching found plenty of talk of weak layers etc, but none stating that rain was a cause of these layers. This is the part that I'd like more info on.
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Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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@beeryletcher, I'm no expert but my thinking is if it freezes solid due to rain then the new snow wouldn't bond with the old which would lead to a week layer....if it turns to snow and lands on the wet snow without freezing then higher chance of bonding...
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You need to Login to know who's really who.
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Guys, next time you are somewhere cold try sticking your tongue onto ice and see what happens
Do you get the picture? What do you think happens to new snow? The same thing.
Ok avalanche 101
What causes skier triggered avalanches?
Yes, a weak layer collapse in the snowpack. No weak layer, no skier triggered avalanche. You may get natural avalanche activity but a skier weighing 80 kg (ok maybe 100kg for the average snowhead) is neither here nor there to a layer of snow weighing thousands of tons sitting on top of ice, grass or frozen dog poo.
What is a weak layer?
1. fresh snow - yes the first flakes can themselves form a weak layer. This kind of weakness lasts 24-48 hours after new snowfall before everything consolidates. Hence the old adage of not skiing immediately after new snow.
This layer is due to fresh snow 
2. surface hoar - caused by cold, clear nights with a temperature gradient (TG) at the surface of the snow. New snow, wind etc can destroy surface hoar so you often get significant spatial variability with this layer. Glades are frequent places you'll find this weak layer.
3. Facets - temperature gradient in the snowpack causes sublimation. Snow crystals turn into facets (depth hoar, faces planes, gobelets) which then form a weak layer. This is the crystal's final state, removing the temperature gradient won't transform the crystals back into rounds or whatever. So they persist for the entire season until:
i. there is a thaw and they melt
ii. it rains and the rain percolates through the snowpack and destroys them
iii. significant new snow can bridge this weak layer, making it insensitive to anyone passing on top - until you hit a weak spot
So yes, rain stabilizes the snowpack. Rain will percolate through the snowpack to the ground.
You get strong temperature gradients in thin snowpacks with long periods of anticyclonic weather. They may also occur across crusts - which is why you may see avalanches break on an ice crust. It is not the snow sliding off the ice due to the weight of a paltry skier but a weak layer collapse above the ice triggering the avalanche. But you don't automatically get weak layers forming around crusts.
I've ignored natural avalanches where rain can lubricate a slab and the base layer/ground and overload the slab. Don't picnic under slopes prone to natural avalanche activity.
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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@davidof, admirably clear and a couple of funny photos for bonus points. Thanks.
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You'll need to Register first of course.
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Thanks @davidof every day is a school day. That's a lot of learning for me for a Saturday!!
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@davidof, thank you - good and clear.
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Looking great across the Dolomites this morning after rain low down on Friday turned to fresh snowfall yesterday, many resorts open today with fantastic early season conditions...
Not a huge amount in the forecasts, but low temps this week should allow for contined snowmaking as seen in the bottom left of the image...
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You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
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The 10th-11th timeframe looks like another warmup on GFS and ECMWF (including ensembles as well) with some precipitation; looks like will be another rainy washout with freezing level ~2500m in parts of the alps
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“Rainy washout” is a bit extreme isn’t it, @ajcrski? Certainly nothing on the horizon compared with last year!
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