Will it be enough for a powder alert?


By meteomorris on 14 January 2020 · 4

Below you will find the most important additions to my article from yesterday (read it again to fully understand the following). High pressure has been dominating the weather for weeks, but at the end of this week a storm will find its way to the Alps. The most important questions: will it be enough for a powder alert? Will there be more storms afterwards? In this articlee:

  • Friday-Saturday-Sunday-Monday: finally a new storm
  • Will it be enough for a powder alert?
  • Long term: is there light at the end of the tunnel?

Friday-Saturday-Sunday-Monday: finally a new storm

The above picture looks hopeful, but it is the small storm Heiko that will cause the breakthrough. Below you can see how that works. Although Heiko is following the same path towards Scandinavia, smaller storm depressions will develop in the elongated front. They manage to reach the Alps on Friday and later return as a Genoa layer on the maps. A classic cold front from the west with a Retour d'est as a result.

But anyone who has been following my weather and snow reports for the last 15 years knows that these are complex storms that make it difficult for the models to calculate a solid forecast. This is the reason which causes all the dynamics in the output of the models the ast few days. It is not without reason that I am reluctant to launch a powder alert and wait until all details are clear and that has three reasons:

  1. Where will the sweetspot be? How much to expect?
  2. Cold on old: does it get deep enough
  3. High risk of storm slabs (= avalanches)

Which doesn't mean that you can ride powder this weekend and the days after. But choosing your destination too fast can result in dust on crust. Which would be a shame.

Where will the sweetspot be? How much to expect?

The jet stream is the engine behind the snow this weekend, but it staggers above the Alps and loses its power there. That makes it difficult for me and for the models. The most logical forecast would be a front that goes into the Alps on Friday from the west. First of all, the current is southwest, which immediately turns to northwest when the cold sector is moving in. Most snow then in the northwest of the Alps. At the same time, a Genoa storm will be created south of the Alps. Which means that the upper air flow will turn from southwest to northwest to northeast to east. This Genua storm in particular makes it incredibly complex. We are now at least 96 hours before this event will take place and therefore it is wise to hold your horses Yes, it is going to snow in the Alps and yes there are significant amounts of snow in the air. But where exactly how much? I'll come back on this later. For the time being, I assume 20-40 cm in the northwest and north, with possibly significant higher accumulations in the western and southern Piedmont.

Cold on old: is it going to be deep enough?

Then there is this second problem. In the best case there will be 20-40 cm of fresh snow and maybe even more in the Piedmont. But the storm for the Piedmont is expected to arrive Sunday-Monday and that is just too late for many because Monday will be the start of another working week. Then move to the north and northwest? The quantities and exact locations are not yet certain and in this case the what I call: cold on old snow plays a major role. The cold snow that will fall on Saturday will fall on an old, often hard and wind battered snow layer. In such a case you need at least 25 to 40 cm of fresh snow to make sure that you track your lines without hitting the old snow layer. So only the sweetspots that will get the biggest accumulations will get enough fresh snow to make it deep enough.

High risk of storm slabs (= avalanches)

Conclusion: it can still go either way. That a storm will follow, that it will be colder and that snow will follow, can now be said with certainty. But where you want to be when the upcoming storm is far from saying. In short, hold your horses. And again when the snow starts falling, a warning is in place:

Fresh snow is on its and this will surely cause a lot of powder pabic. But fresh snow on an old snow layer also guarantees problems. In case of new snow, take a rapidly rising avalanche danger into account. Especially storm slabs will be a problem. To prepare yourself already, it might be a good idea to refresh your knowledge with our Mountain Academy.

Long term: is there light at the end of the tunnel?

Although the models are pretty dynamic where it will snow next weekend, they seem fairly unanimous about the longer term. After the weekend, high pressure would again lie above the British Isles. With this, storms with a large arc are directed towards the north of Europe. But a glance at the NAO index indicates that it will become less positive in the coming period. A neutral or negative index offers room for cold (er) air from the north and storms that reach the Alps with snow. Also read again this article from several years ago back.

Provisional conclusions:

  • mild and sunny until Thursday
  • a new storm as of Friday but the location and amount of snow is still guessing (PA # 7?)
  • please note: increased avalanche risk
  • does that storm in the Mediterranean offer hope? (PA # 7 or 8)
  • long term: nao index negative? Let's hope so.

Last but not least, I want to ask you to read and where possible support Erik Bulckens' dream. Erik Bulckens is a cinematographer, documentary maker and powder fanatic. Thanks to wePowder, he has been scoring powder for years. His dream is to make a movie documentary about the people behind wePowder. For that, Erik needs your help. You can read all about it here: read here. Do you help Erik make his dream come true? Thank you very much for your help!

Morris

Comments


  • meteomorris
    Expert
    meteomorris op 14 January 2020 · 21:19
    The new runs are looking good!
    May the powder be with you.
  • Ehrnst
    Ehrnst op 14 January 2020 · 21:34
    Hi Morris

    Great work👍👍👍
    When and how Ofoten do you run the models/forecast we see ?
    ( going 4 days next weekend soo this is really going on My nerves😳)
  • sparymcm
    sparymcm op 14 January 2020 · 22:03
    The new runs are looking good!meteomorris op 14 Jan 2020 21:19

    Good for where? The suspense is killing me! These posts this week have been awesome, thank you!
    *message edited by sparymcm op 14 Jan 2020 22:08
  • Brock22
    Brock22 op 15 January 2020 · 15:13
    Hey Morris,
    I notice that Meteoschweiz are not predicting much precipitation for the coming weekend. What model do they use for the forecasts? Why is there such a difference between theirs and other forecasting services?
    Off to the Berner Oberland on Friday and hoping for some snow.

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