The All New Weather Outlook 24/25

A snowHead

La Plagne - ECMWF median values show significant precipitation for Thursday, then from Sunday to Tuesday. Rainfall equivalents:
2/1 - 20mm
5/1 - 10mm
6/1 - 20mm
7/1 - 20mm
Mild on 5/1 and 6/1, so a question of altitude.

A snowHead

Nervous for washout next week in North west need things to push a little further south for a very different outcome . Thus pesky tropical air to the south again this year

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@Le Grand Renard, the air is always tropical down there of course, it's the tendency to develop azores-iberian lows that's been the ruin of many a good pattern recently. Although we got lucky last time. And should be fresh 10-15cm in valleys by 3rd.

Flicked thru 9 model Op runs, and while 5-6th warm up is pretty much baked in, am none the wiser whether we can end on a good dump around 7-8th.
3 of them are bad, 3 are good and 3 indifferent. Can see the spread just from comparing ECM 00z to its AI version, and looking at the ensemble scatter.
It's all down to how deep that SW low becomes (it's already sitting out in the atlantic now), and how far SE it ends up phasing with the main trough to the north. If it's not too deep, and stays south then we get a very nice dump to the valleys (AI)....but if it blows up (deepens) and heads NE like on ECM 00z Op we'll end up with some damage below 1500-1800m.

Best case for 5-6th now is under 30mm (some forecasts are nearer 100mm), and of course for the snowline to be generally around 1800-2000, although spikes to 2400 are still popping up. Then as above we end with a much lower snowline 7-8th. Think above 2000m is going to see decent accumulations either way, but nothing certain yet.

Looking at the 7-8th means, ECM is actually the best of the bunch (can see it's 00z Op run was a warm outlier), GFS just lagging hopefully, while GEM isn't bad. Need to get some separation between the south atlantic and euro lows to turn the air source towards the north.

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Equating to Thursday/Sunday/Monday blizzards in Avoriaz, VT and Tignes?
https://meteofrance.com/previsions-meteo-france/les-gets/74260

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@polo, thanks for all your valiant work so far this season.

I'm off to the Dolomites on the 11th. Forecast seems to be all over the show there from decent dump (relatively) to pretty much nothing.

You have a gut feeling on this?

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Can somebody explain how models can vary so wildly from run to run ?

Example: 00z GFs shows substantial snow event, 06z run shows dry as bone, 12z goes back to some snow and 18z again nada ... !?

I am talking 7 days in advance - not 7 weeks !?

With so much yo-yoing it makes me lose faith in meteorological science Sad

Slightly sarcastic but still serious question ...

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Please God snow Thursday and Friday and then sun - Zu Zu petals and I want to ski again in the Sun - name the movie that part of that came from
Clue- its a Xmas movie
Happy New Year to you all

It sure is a wonderful life Eh oh!

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@8611, thanks! Yes, not worried about the quality of the snow on piste but ideally would like it looking nice and wintery, with sunshine at some point too though, of course Very Happy

Would prefer winter than sun tbh. Skiing through brown terrain in January is just depressing. Will watch this thread with interest over coming days. I think there will be a fair bit of sun around anyway.

You know it makes sense.

Temperatures look very up and down over next week. Showing max temps for Tignes going from -5 to +5 and back to -5 within a few days.

Should be some top ups of snow but might also be some wet stuff lower down on Sunday/Monday.

Otherwise you'll just go on seeing the one name:

A snowHead

Freeze level is going to shoot up almost 3000m from fri to sunday but miraculously it seems the alps will avoid most of the heavy ppn coming up from the SW. Still could see 20-30mm I’d guess from ensembles, hopefully less but at least we’re not seeing very big numbers any more.

Here’s GFS and GEM on Sunday 5th, maybe snow for uk, and rain just north of alps

Monday 6th also starts warm with better agreement now for cold air to arrive by the evening from the NW, so 7-8th looking ok for snow to low levels, before another round of phasing drama potentially. But let’s see how the first one goes this weekend before thinking too far ahead.
Here are the means for 8th, good to see the isobars over France don’t link up as much with the Azores. Still a bit marginal though, with milder air never far away.

Re.southern alps, yes they could see snow as well 7-8th, some runs even have a brief genoa / med low, but a week is too far to rely on such detail and it’s not consistent at the moment. Further out a few models hint at high pressure moving in over uk, with cold easterly flow toward alps / med. But again just one of several options at that range.

A lot of uncertainty as this pattern plays out for at least a week, so the detail from the models is less reliable than usual beyond days 4-5.
Overall model accuracy seems to have plateaued in recent years after the big improvements in previous decades. And while AI models seem to be slightly overtaking the physics ones, it’s surprising really as they are based entirely on mimicking previous patterns over the last 50+ years afaik, as you’d think the climate is very different now and not something that analog data would be able to model well.

A snowHead

Oh man,

all I am reading from this is:
"guess"
"not consistent"
"hopefully'
"options"
"uncertainty"

Instead I would like to read something like "30cm for Dolomites, 70/80cm for France, daily dusting for Switzerland and sunshine after dump (of snow) for Austria ... oh well ... anticipation and excitement before upcoming trip is driving me nuts !

I wish you all Happy New Year and thank you for great information, great work and keep it up in New Year!

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@Cheapski, you'll get more concrete info 24 hours before a forecasted dump!

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What sort of weather patterns benefit places like Montgenevre? With it sitting on the Italian/French boarder, does it tend to get more snow when the eastern side of the (southern) ridge is getting snow, or from the (north)west?

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Bit of both for Montgenevre. It is a bit shelter from receiving super heavy totals but can do well from all directions. On the flip side, it is a lot more snow sure than other resorts in the French and southern alps.

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Cool, thanks. So it's a fairly snow sure resort, but not usually one to have bumper depths?

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Yes, it’s rare it rains up there during winter. It doesn’t get the same totals as places like Tignes, Avoriaz etc.

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I have a trip booked for the NW Alps in Switzerland Jan 25 - Feb 2. How far in advance would I start to have an idea of whether the snow will generally be good or not?

Does the weather this far out make much difference or does it only really matter what happens closer to that week? Wondering how much I should care about the current snow forecast affecting my trip.

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Despite all modern forecasting techniques meteorologists still admit that accurate forecasting beyond 3 days is very limited…..the charts from the models that are discussed and analysed here that give forecasts up to seven days out are interesting to read but how often are they correct….?

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You’ll have a general idea of it will be high or low pressure dominated around 7-10 days in advance.

Eg currently there is a developing signal that from around the 12th there will be high pressure over Europe. This could be centred in Iberia or Scandi, which will dictate the temperature but it is likely to be dry.

Up until then the weather is unsettled with fronts approaching from the NW/W, offering a mix of rain and snow.

If you want specific on whether there will be snow on a certain day, probably 3 days.

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@Sneachta2013, all models are wrong, but some are useful

Addressing some questions above, skill scores depend on the metric and scale....it's easy enough to predict wide scale pressure anomalies in the 6-10 day range, less so temperature or precipitation for small areas such as alps, and also complicated by the actual pattern / mobility of systems.....some patterns are far more likely to verify at day 7 than others.
Quick flick thru this thread will show there haven't been many bad forecasts for the mid range (days 6-10). The mild spell post xmas was well forecast 10 days out, and several dumps for the NW were confidently discussed from 6-7 days out.

Likewise when we get south atlantic lows interacting with north sea lows like the coming week it's harder to make a good call beyond 5 days and hence all the 'if's and buts'.

Plenty of stats available here https://charts.ecmwf.int/?facets=%7B%22Type%22%3A%5B%22Verification%22%5D%7D

CRPSS = 1 the forecast has perfect skill compared to climatology;
CRPSS = 0 the forecast has no skill compared to climatology;
CRPSS = a negative value the forecast is less accurate than climatology.

So there is some skill from the models to forecast temps even out to week 2

And pressure anomaly accuracy is up to 0.8 correlation coefficient at day 7.....although am not sure on the scale, is it within 5km or 50km etc

As for worrying about conditions in 4 weeks time, there's not much point as whatever happens in the next 2 weeks will be overridden in the following 2. Of course we'd rather not see heavy rain in mid Jan, followed by a mild dry spell but even then there would be time for a sudden change. It's only takes one day of heavy snow or rain to completely transform a low lying resort.....so assuming no disasterous spells, and reasonable altitude, there would be nothing to worry about now. I'd start getting interested in potential patterns max 10 days before a trip.

So what's ahead, will start snowing tonight in the NW, 10-20cm likely to 1200m and a bit less at 1000m. Again this one was well picked up by GFS over a week ago.
The weekend mild spell, especialy Sun 5th will see iso close to 3000m, with rain showers possible even above 2200m, but thankfully only looking like 10-20mm.....as a few days ago we had 50-100mm cropping up.
Monday also warm, still on track to have colder air arrive sometime late monday evening. By cold I generally mean 0c at 1500m.
Still looking borderline for the mild/cold boundary, ie how much of the alps will be on the cold side as stuff is falling from the sky....6 main models here showing good consisteny at t+120, or day 5, but it's more westerly than northerly approach means mild air is close to the south and east initially.

So the 7th looks good as the low moves across.....then we have the second round of south atlantic low interference 8-10th....no point in going into the charts or worrying about details as it's pretty messy, but the risk is there once more of a highish snowline.....but maybe the models are being overly progressive, either way I expect lots of chopping and changing again around that time, before this whole pattern finally moves on.

ok snow charts.....last 3 GFS out to tues 7th, UK still looking loaded

also UKMO and ICON to 7th

Some of those figures will be only snow above 2000-2200m, and I doubt they include any losses from rain/compression, but in general looks like snow - rain - snow out to monday, with 20-40cm possible on a wide scale at 1200-1500m NW

You know it makes sense.

If you wanted a particular run to verfiy then the GFS 06z just now shows a great route to cold. But very unlike the milder ECM 00z.

It sees the atlantic hitting a wall on the 9th, N/NE air for alps, with med low.....and then by 12th a deep freeze.

Risky business.... but it's out there as a possibilty

Otherwise you'll just go on seeing the one name:

Would the snow from med low deliver for northern and western resorts, eg 3V, PdS?

A snowHead

@Astontech, typically no, but the first chart above has a mixture so all areas would get something. Less so the second chart with centre of the low to South.

Austria tends to do better than NW alps when the south is getting flow off the Italian end of med

A snowHead

Thanks. I have been charting since the infamous winter of 2010 but it’s taking some adjusting to understand nuance in the alps.

I am out for 3 weeks from Jan 11, La Ros then 3V so have been eyes glued to the output for the last few days with fingers crossed.

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@Astontech, a Genoa Low tends to get nestled in the Southern Arc south of the Alpine Ridge and produces great amounts of snow there , it does creep over the border in the Southern alps , the Maurianne Valley and the La Fornet End of Val D’Isere . Here in Sainte Foy we are watching distance of the snow but it very rarely gets here because of the Forhn effect and geographical reasons .

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Here comes the snow snowHead

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Chamonix meteo forecasting another 80-100cm over the next week. And for the doubters, he was pretty much spot on at the same point for the last storm, with his 120cm forecast.

HNY to all Happy

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duplicate post

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@Snow&skifan, Note the important line at the bottom of the Chamonix Meteo Forecast:

Fiabilité de la prévision : assez bonne jusqu'à vendredi ‑ médiocre pour la suite.

Reliability of the forecast: fairly good until Friday - mediocre for the rest.

@kitenski, that's pretty typical of his forecasts; he's clearly read the regular health warnings on this thread, regarding accuracy of forecasts >3days out Happy

I'll happily take mediocre forecasts of snow, over accurate forecasts of rain snowHead

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@Snow&skifan, Umm don’t know where the disappearance of rain has come from ?

Chamonix Meteo issue a western alps forecast every afternoon link below

Seems to be plenty of everything coming our way as of this afternoon’s forecast a real rollercoaster .

https://meteo-chamonix.org/

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The All New Weather Outlook 24/25

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