Temporarily calm weather after an intense storm cycle


By meteomorris on 23 January 2018 · 4

The 10 day storm cycle with varying temperatures, lots of fresh snow and rain has come to an end and resulted in major changes in the snow cover. A high pressure area will keep storms at distance until Thursday. It will be sunny, dry and pretty mild (especially on Wednesday during the day). The snow cover can radiate and cool down during the clear nights. A new storm is approaching the Alps on Thursday afternoon. A warm front from the southwest will first bring a lot of snow south of the main alpine ridge. The Alps might get into a snow sandwich after that, but that's not certain yet. PowderAlert #12 is in effect from Friday, but the window is short, with mild air entering the Alps on Sunday. In this forecast:

  • Weak cold front after a warm front
  • Avalanche danger decreases, but still critical conditions
  • Tuesday will be sunny, Wednesday very mild
  • New storm on Thursday/Friday
  • Mild temperatures from Sunday

Weak cold front after a warm front

An intense storm cycle has come to an end. Rainer Feldner sent us the stats from the measuring station in Elm (Switzerland) where 344 cm of fresh snow came down in 7 days. Based on this measuring station, I would briefly like to walk you through the storm cycle from last week. Especially because it is too easy to only look at the amounts of snow. Here you will find a link to the measuring station.

Source: SLF
Source: SLF

You can check out the development of the snow cover in Elm above. 344 cm of fresh snow came down in 7 days. An amazing 173 cm of fresh snow even came down between Sunday and Monday morning. Nevertheless, the snow cover 'only' grew with 73 centimeters. Because snow consists for 90% out of air, the snow cover settles itself under the influence of temperature, wind and its own weight (check out this article).

But what the graph above does not show is the development of the temperature. Fortunately, there's more data available. Four warm fronts caused the temperature to rise rapidly. There are clear peaks in the temperature on Tuesday 16th, Thursday 18th, Saturday 20th and Monday 22nd. Rising temperatures are a typical red flag in avalanche science. A rapid increase in temperature has a negative effect on a snow cover, because its weight increases and the precarious balance can be disturbed.

The last warm front of January 22nd is also clearly visible. It resulted in a rising snow line and rain in a lot of places (locally up to 2000 meters). Monday was therefore a very critical day. A lot of snow already came down and another 80-150 cm came down between Sunday morning and Monday evening. This snowfall came with rising temperatures and this resulted in extreme avalanche danger. Snow that falls with a temperature of 0 or -1 degrees is heavier than snow that comes down with -5 degrees. It means that the more heavy snow fell on top of the lighter snow. This always results in a rising avalanche danger. Fortunately a weak cold front came in on Monday afternoon and this allowed the snow cover to stabilize a bit, but the conditions remain critical.

Avalanche danger decreases, but still critical conditions

The avalanche danger was HIGH and even EXTREME in the northern French Alps, Switzerland and the west of Austria on Monday. It's a pretty unique situation. When the avalanche danger is EXTREME there is an immediate threat. Roads are closed as a precaution and villages are temporarily cut off from the outside world. It was even decided to temporarily evacuate the residents of a number of houses in a few villages on Monday. Check out the video below from Ischgl.

The avalanche danger is now HIGH in large parts of the Alps. Because of the large amounts of snow, it is expected that the snow cover will set itself because of its own weight in the coming days. That doesn't mean that there's no danger anymore. Avalanche danger HIGH (4 on a scale of 5) and EXTREME (5 on a scale of 5) are a threat to public life and might result in the closure of roads etc. We still have to deal with the risk of wet snow avalanches, wind slabs, a snowed in layer of surface hoar in the east of Austria and the rapid warming of Wednesday.

There's still plenty of fresh snow to be found above 1900 meters in the west and 1500 meters in the east of the Alps. Hereby some advice to reduce the risks:

  • prepare yourself, make sure you have the right knowledge and use that knowledge
  • read your local avalanche forecast and adjust your plans to it
  • always ride with avalanche beacon, shovel and probe
  • ride with powder friends
  • pay attention to the rising temperatures the next couple of days

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Tuesday will be sunny, Wednesday very mild

A weak cold front arrived in the Alps in the night to Tuesday. It has temporarily become a bit colder and there is some last snow coming down in Austria. Meanwhile, the Alps will have to deal with high pressure and the sun comes out. The sun is already shining in the west, but it's still overcast in large parts of Austria.

Still cloudy in Lech
Still cloudy in Lech

Already sunny in Zermatt
Already sunny in Zermatt

Mild air arrived in the west of the Alps on Tuesday afternoon and at the same time the sun comes out in Austria. Mild and dry air is sent to the Alps by a current from the southwest. This results in a southern Föhn on the north side of the main alpine ridge and a rising freezing level.

The freezing level will rise towards the 2700 meters in the western Alps and about 2200 meters in the eastern Alps on Wednesday. Because the air is pretty dry, this will have no consequences on shady faces, but it should be taken into account that the snow cover on sunny slopes might become very unstable during the day, which can have consequences for the opening of roads and ski areas because of the enormous snow cover. Fortunately, the nights are clear and cold and that gives the snow cover a chance to stabilize again. The Alps will have to deal with mild, but dry air till Thursday.

New storm on Thursday/Friday

A new storm will follow at the end of this week. According to the latest calculations, this results in a southern stau, possibly followed by a snow sandwich, although that is not yet certain. Because the low-pressure area responsible for this is very close to the Alps, minor changes can have major consequences. You can find the scenario that is calculated for the coming days below:

The storm in three steps. Check out the numbers above:

  1. Cold air tries to move south (blue arrow), and at the same time warm air tries to move north (red arrow). This warm air results in a Föhn from the south on the north side of the main alpine ridge with mild temperatures. At the same time, it starts to cool down (orographic cooling) on the south side of the main alpine ridge.
  2. A new depression develops near the dividing line of hot and cold air. Cold air is trying to fight its way in on the west, but the current turns to the south and clouds are being pushed to the south side of the main alpine ridge. The storm makes its appearance and it starts to snow south of the main alpine ridge. The first snow will fall south of the Gotthard and the Monte Rosa on Thursday afternoon with a snow line around 800-1200 meters. The precipitation expands in the night to Friday.
  3. A Genoa depression arises. Warm and cold air move above the Alps. Timing and exact position of the fronts can still slide in the coming days but for now this is the scenario: lots of snow south of the Gotthard, Simplon Pass and the Monte Rosa. It comes to large quantities of fresh snow. Snow line locally dropping to 400 meters. The precipitation on the south side of the main alpine ridge is expanding towards the rest of the Italian Piedmont and the southern French Alps. Whether and in what form a snow sandwich follows is still uncertain.

Pre advice PowderAlert #12

Because of the proximity of the low-pressure area it is difficult to say what the exact course will be. For the time being, the northern Piedmont and the west of Ticino seem to be a safe bet to score powder on Friday and Saturday. The French southern Alps and the western Piemonte also are a good option, but there is still some uncertainty. Therefore, do not be fooled by the short-term calculations of our snow maps. They can still change the next couple of hours. If you can not wait with booking an accommodation, go for the Northern Piedmont. There's a high chance of riding powder there.

Mild temperatures from Sunday

It will be mild again in the Alps from Sunday. High pressure returns and the weather will be like that till the middle of next week.

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Stay stoked, Morris

Comments


  • ChaletRafalt
    Tourist
    ChaletRafalt op 23 January 2018 · 19:24
    Hey Morris. Thanks as always for the scoop!

    Is it possible to provide a link like you did for Elm to see how much snow came down on Galzig in the Arlberg? No worries if not, I know you are busy!!
    ChaletRafalt
  • seannolan9
    seannolan9 op 23 January 2018 · 19:55
    Hi Morris
    We’re a group of old boarders traveling to Alagna on Thursday. When would be the best day for guiding? We stay till Tuesday 30th
    Keep up the good work bro
  • meteomorris
    Expert
    meteomorris op 23 January 2018 · 23:41
    @seannolan9 I would say Sunday/Monday
    May the powder be with you.
  • meteomorris
    Expert
    meteomorris op 23 January 2018 · 23:44
    @ChaletRafalt on this page you can find links to all the nearby weatherstations at the Arlberg region. Including Galzig. https://wepowder.com/en/ski-arlberg#elevation
    May the powder be with you.

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