Dare to ask: weather and snow, how does that work?


  • meteomorris
    Expert
    meteomorris op 31 mars 2020 · 09:30
    It is still winter in the mountains, but Corona keeps us at home.
    I wonder what questions you have about the weather and snow in the Alps.
    Looking forward to your response.
    Know where to go!
  • 00fra00
    Advanced
    00fra00 op 1 avril 2020 · 11:43
    Hi Morris, I have the following question for you:

    I've always been curious to understand the dynamics involved in the production of different types of snowbeds (from dense and heavy to the cold smoke).
    Considering the different types of weather cycles, but focusing especially on the geography of the alps, since I can't help noticing a huge difference between the north and south side of the main alpine ridge, or in some cases moving from the inner alpine toward the prealps.

    In fact, I live on the south side and here finding low-density snow seems way more difficult than what I've been able to achieve on my powdertrips up north.
    (Maybe the proximity to the Mediterranean sea has an influence...).

    Thank you
    Regards
    Fran
    Francesco Cesana
  • meteomorris
    Expert
    meteomorris op 1 avril 2020 · 14:01
    @00fra00 snow is basically a lot of air. In a normal situation 1 mm of water produces 1 cm of snow. So there is a lot of air in a snowflake.
    The density of snow is all depending on what they call the snow-water content. Heavy snow has a high water content and light snow has a low water content.

    A normal storm produces snow that has a water content between 7 and 11 %. In other words: 89 tot 93% is air. Light snow has a water content less than 7% and heavy snow more than 11%. To put this all in perspective: man made/artificial snow has a water content around 24-28 percent.

    What does this mean? For 1 cm of man made snow you need 2.4 to 2.8 mm of water. For cold smoke you need less than 0.7 mm of water. There have been storms that produced incredibly light snow with a water content near 3%, which means that 0.4 mm water produces 1 cm of snow. Or better said 1 mm of water produces 2.5 cm of snow with 96% air in it.

    For cold smoke you need very cold air. This cold air could be transported towards the Alps with a northern or eastern upper air flow, but can also be available in the Alps. Especially the inner alpine areas do have a fairly dry and cold climate during high winter. Cold air sinks into these valleys and since this air is heavy and the angle of the sun is pretty low in high winter this cold air layer might be present until spring kicks in.

    Scenario 1: northern or eastern upper air flow
    Cold air moves in and the last cm's of a snow storm will be of lighter snow. We see this mostly on the Northern side, but sometimes also in the Piemonte when cold air kicks in the Po valley and pushes clouds towards the western and southern Piemonte.

    That having said: on the southern side of the Alps chances for blower pow are bigger in the Piemonte than in the Dolomites since the Dolomites mostly have a warmer southwestern airflow that brings snow.

    Scenario 2: a mild enough but not to mild storm moves in which ensures very cold snow lower on the mountain.

    Something to be aware of in all scenario's: wind!
    Know where to go!
  • 00fra00
    Advanced
    00fra00 op 1 avril 2020 · 15:01
    Thankyou
    You solved many of my doubts and yes sometimes wind can make your day but many other times it just ruins it.

    Next time I see a retour d'est on the map I'll try to catch it in time
    Francesco Cesana
  • meteomorris
    Expert
    meteomorris op 1 avril 2020 · 15:03
    @00fra00 where did you ride most of the time when you mention Northern and Southern resorts?
    *message édité par meteomorris op 1 avril 2020 15:03 (3% bewerkt)
    Know where to go!
  • 00fra00
    Advanced
    00fra00 op 1 avril 2020 · 22:41
    Mostly around Lombardy, Graubunden and Tyrol.
    My main two bases are the Passo Tonale and Engadin, but I can't stay away from St Anton or Laax which are my favorite resorts in the alps(at least when there are few crowds).

    If next season you come around down south I will guide you through the tunnel😜
    Francesco Cesana
  • meteomorris
    Expert
    meteomorris op 2 avril 2020 · 11:53
    00fra00 Thanks! You mean the tunnel at Passo Tonale?
    Stay strong and healthy!
    Know where to go!
  • 00fra00
    Advanced
    00fra00 op 2 avril 2020 · 22:04
    Yes, that one. I remember you mentioning it a couple of times
    Francesco Cesana
  • 00fra00
    Advanced
    00fra00 op 2 avril 2020 · 22:06
    Francesco Cesana

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