PA #10: 1 to 2 meter of fresh snow!

By meteomorris on 9 January 2018 · 0

I started the day with a fresh espresso yesterday and that's no different today. To make a cappuccino, you just have to put your cup outside the window and before you know it there is a white layer on it. It's dumping like crazy in the Italian Piedmont, the Aosta and the neighboring areas in Switzerland (the south of Wallis) and France (Queyras, Haute Maurienne and Haute Tarentaise). Check the live blog here!

The snowfall was (as expected) a bit humid yesterday, but colder air arrived in the Alps last night and the snow that will fall in the morning will be colder. The heavy snowfall will come to an end in the Piedmont after lunch and moves via Lombardia towards the east of the Italian Alps. Many lifts are still closed today due to high or even extreme avalanche danger, but the snow masses settle quick and I expect more lifts to open tomorrow and the day after tomorrow. It remains cold enough to keep the snow fresh. If you have time I would get down there! In this forecast:

  • 1 to 2 meter of fresh snow
  • From (south)east to south
  • Snowfall is moving east and it remains cold
  • PA#10: Where to go?
  • Mild and Föhn storm in the rest of the Alps
  • Sunny in the south from Wednesday, residual clouds and some flakes in the north
  • A new storm during the weekend?

1 to 2 meter of fresh snow

It's dumping like crazy in the Italian Piedmont, the Aosta and the bordering areas in Switzerland (the south of Wallis) and France (Queyras, Haute Maurienne and Haute Tarentaise) since Sunday afternoon. As I wrote yesterday, I do not often use the word dump anymore, but this definitely is a dump.

I explain to you in the above video weather message from Friday from 2:34 why it is dumping so heavily right now. In short: a storm that initially was above Spain is moving very slowly towards the Alps. At first instance, this ensures a southeastern current. Although the supplied air is warm and contains a lot of moisture, the collision with the south side of the Alps result in a rapid temperature drop. The combination of intense precipitation and fast rising mountains ensures sufficient orographic cooling to ensure the snow line drops to about 1200-1500 meters on the south side of the Alps, but the freezing level is hundreds of meters higher. The snow initially is pretty humid up to high altitude. However, due to the continuing orographic cooling, the snow becomes drier because the temperature drops on the spot.

At the same time we see those heavy clouds creeping over the main alpine ridge. Normally they do not stretch that far, but because it is relatively warm and they contain a lot of moisture, they can reach deep into southern Wallis, the Queyras, the Haute Maurienne and Haute Tarentaise. There is still some cold air in narrow valleys here and it's snowing heavily. It snowed so hard that in the Piedmont and neighboring areas the avalanche danger is now EXTREME. That's already the second time in 2018 and that is very, very exceptional. Check out the footage below and more images in the live blog.


A lot of snow came down in Tignes and Val d'Isère last week and they got a lot of snow from this storm as well. The combination of snow from last week (Tignes is above 2000 meters and saw mostly snow and practically no rain) and the snowfall pretty much disrupts daily life.

Huge amounts of snow
Huge amounts of snow

Between 1 to 2 meters of snow already came down since Sunday afternoon and locally even more. According to the measuring stations, the snow cover grew about 1 to 1.5 meters above 1900 meters, which (especially because of the heavier snow at the start) means that about 1.5 to 2 meters of snow came down. Check out this article how the snow slowly settles.

160 cm thicker snow cover in Via Lattea
160 cm thicker snow cover in Via Lattea

The diagram below clearly shows what we explain in this article. 23 + 76 + 113 = 212 cm of fresh snow came down since Sunday. At the same time, the snow cover grew from 228 to 354 cm. The snow cover thus 'only' grew 126 cm. In short, the snow that falls always settles. You can also find the diagram above here. It is a station in the southeast of Wallis, not far from the Simplon pass.

212 cm of fresh snow
212 cm of fresh snow

A lot of snow came down in the core areas mentioned before, it was still snowing in the night to Tuesday, but not that intense anymore and it also started to snow in the French southern Alps due to the incoming cold air and the current turning from the east to the southeast.

A retour d'est? No, not really

Can we call this a retour d'est? Yes and no. Yes, because the snow clouds come in from the east. But it is not a real retour d'est. You can read everything you want to know about a retour d'est in this article.

A 'retour d'est' is a French name for a phenomenon that is mostly happening in the Italian Piemonte. Literally translated, it means a return from the east. A true 'retour d'est' is created as cold air finds its way to the Gulf of Genoa through the Rhône valley and the French Alps. Once it arrives in the Gulf of Genoa this cold polar air hits the (relatively) warm and humid air above the Mediterranean and small, but very active storm depression is formed. This is called a Genoa-low.

There's no question of a return from the east and certainly not a Genoa-low in the storm from Sunday till today. This was a major depression over Spain that triggered a huge southern current. A situation where the jet stream collided with the Piedmont with a southeastern angle. That is quite unique and very, very rare. The fact that the media name it 'Retour d'Est' is okay, but it's not really a 'retour d'est'. That's also because of the snowfall in the southern French Alps last night and right now. On the approach of the storm suppression from Spain the wind has started to shrink and turned from south-east to south.

Jetstream turns to the southwest
Jetstream turns to the southwest

Cold front arrives in the French southern Alps from the southwest
Cold front arrives in the French southern Alps from the southwest

In short, the very strong jet stream that hit the Alps results in a current from the southeast (because of the storm depression above Spain), and clouds are pushed full force against the Alps and forced to snow empty. Due to the orographic cooling, the snow line dropped rapidly and on top of that, a cold front came in in the night to Tuesday. A unique situation, because we do not often see a jetstream path like this (check out my video forecast from Friday if you're lost by now). Do you have questions about this? Do you want to understand it better? Shoot! I like to answer them.

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From (south)east to south

In short, the jet stream begins to lose its grip on the Alps and moves to the east. The enormous storm depression slowly dissolves and the wind turned from south-east to south-west last night. It stopped snowing heavily in the Piedmont and it started snowing in the French southern Alps, Lombardia and later also the northeast of the Alps. Because the jetstream is now moving to the east rapidly, the intensity of the precipitation also decreases rapidly.

At the same time the Alps will have to deal with colder air. The supply of mild air from the Sahara has stopped and the air that is pouring in now caused snow in Spain on Sunday. It gets colder and the snow that falls now is light, cold and dry. A typical 'cold on warm' storm. The ideal combination for a PowderAlert. Check out this article: this dump in the western Piedmont has a perfect score (5 out of 5). It's a perfect storm. It is true that a lot of snow came down, but the advantage of a lot of snow is that it sets itself faster by its own mass.

PA#10: Where to go?

I've already published a list of tips where to go on Friday. That list is still going strong. If you want to ride powder, check out this article and you know exactly where to go. It's snowing till today, and the sun will come out tomorrow.

I still have some additions to the choice of your area:

  • Ride on the slopes today!
  • Choose ski areas with many treeruns. They had less wind in the trees and on the lower parts of the mountain
  • Stay away from those parts of the mountain with larg open and steep faces
  • Listen to the mountain rescue and avalanche controllers!

The snow cover will start to set rapidly due to the mass of the snow cover from Wednesday. In addition, it gets sunny and the wind is lying down. The riding in the trees will be great until this weekend, when you stick to the local avalanche forecast and adapt your plans to it.

Sunny in the south from Wednesday, residual clouds and some flakes in the north

The current from the south will end from Wednesday. Cold air will arrive in the Alps and sun and clouds alternate. Possibly you can expect some light snowfall and some residual clouds in the north, but I expect that the sun will dominate.

A new storm during the weekend?

There's a new storm coming in this weekend, but the question is how powerful it will be and if it will reach the Alps. The following is being calculated right now:

  • Snow for the Italian Alps. Sweetspot and intensity is still not certain, but for the time being it's the Piedmont (again) and Lombardia
  • After that there are two scenarios. 1. It keeps snowing in the south, 2. There is a snow sandwich with snow for the entire Alps.

Enjoy PowderAlert #10, but always ride with your head! We are dealing with an exceptional storm that will give you enough powder pleasure later this week.

Stay stoked. Morris


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