Off Piste Snow Report – N French Alps – week starting 19th February 2024

A dry and sunny start to the week predicted for the N French Alps & surrounding areas. Snowfall expected towards the end of the week, hopefully down to lower altitudes! 

It’s a similar story to the last two weeks, with predictions of big snowfalls again being pushed back to the end of the week. Again, different weather forecasts are showing different stories, so time will tell! If any significant fresh snowfall (20 cm or so) does happen though, this will make for a very worrying period of snow instability at higher altitudes, especially on the colder N’ish facing slopes (see below for more info on this).

There’s a massive contrast between natural snow depths at ‘mid-mountain’ altitudes of 1350 m or so and ‘high-mountain’ altitudes above 2400 m.

Thanks to plenty of pre- and early season snowfall at high altitudes, depths of natural snow above 2000 m are normal for the time of season, especially above 2500 m, where they are actually higher than usual.

Even after a few sprinklings of fresh snow last week, there’s now very little, or no, natural snow coverage at altitudes below 1400 m on N’ish facing slopes, and below 1800 m on S’ish facing ones. Unfortunately, the rain/snow limit has been quite high (1800 m or so), washing away much of the natural snow at mid-altitudes. The piste grooming teams have been working very hard to make sure the pistes are skiable for this peak holiday season.

Best conditions can be found at high altitude resorts, e.g. Tignes, Val Thorens, where snow coverage remains excellent.

Avalanche Bulletin

The current avalanche danger level remains  a ‘limited’ 2 out of 5, across most of the N French Alps and surrounding areas. I really think it should be a ‘low’ 1 out of 5 because of how stable the overall situation is, except maybe in the afternoons with the higher temperatures.

But, in my opnion, the predictability of potential avalanche activity following rising temperatures (and the tiny percentage of accidents due to natural wet/humid snow avalanches) should not dictate an increase of a full danger level.

HOWEVER, for the next precipitation event (snow forecast for the later part of the week for example), things will become very-extremely unstable on North’ish facing slopes above 1800 m or so. See the ‘Propagation Saw Test (PST)’ in the video below, carried out by Alain Duclos of Data Avalanche on a NW facing slope at an altitude of 2075 m.

The test demonstrates a persistent weak layer which has formed in the snowpack on N’ish facing slopes and shaded slopes as a result of the clear skies that have dominanted the weather conditions over the past 3 weeks. 

Alain commented that is was

“A positive PST (after a relatively long initiation time), despite the modest altitude (2075 m). Gradient metamorphoses are active in the shaded slopes despite the often high air temperatures” (but low snow surface temperatures especially at night thanks to the clear skies over the last few weeks). 

It’s interesting to note that this temperature gradient metamorphosis (the process that changes the snow layers into the weak sugary ‘faceted’ snow **) is now showing production of serious weak layers at altitudes as low as 2000 m in shaded areas.

We keep mentioning the need to pay extra caution around the colder shaded and North’ish facing slopes.  This is really important at the moment, and these are the places where it will become especially unstable when the next snowfall of 20-30cm or more comes. The vast majority of avalanche accidents involve cold, dry slab avalanches. They’re almost always triggered by the victim (or someone in their group) on N’ish facing slopes (in the Northern Hemisphere) during December, January and February.

** See my in depth talk on triggering.

Weather forecast : Mon 19th to Fri 23rd Feb thanks to Météo Alpes (& a 14 day one from Météo Blue) below:

MON 19th: Sunshine in the mountains with a few cumulus clouds. Possible very light snowfall in the evening (but only a few flakes). 0° C at 2000 m. Moderate N wind.

TUES 20th: A mainly sunny day in the mountains. O° at 2200 m. Light to moderate NE wind.

WED 21st: Sunny day with some thin high cloud, which will thicken in the evening.

THURS 22nd: Cloud building up as the day goes on. Snow will start falling in the afternoon and continue overnight, possibly down to lower altitudes.

FRI 23rd: Snowfall will continue in the morning, dying out as the day goes on.

NEXT FEW DAYS: Unsettled.

Tip of the Week

Sun Shadow Slope Orientation

Since I so often talk about N’ish facing slopes (the vast majority of avalanche accidents happen on the North’sh side of the mountain – cold, dry slab avalanches triggered by the victim), and due to popular demand, I am posting this TOP TIP on using shadows to identify slope aspects (below). Also when any fresh snowfall arrives (as is forecast for the end of this week), high N’ish facing slopes are where the danger/sensitivity to triggers will be most prevalent.

SPECIAL HAT OFFER

1. To help you keep things acceptably safe off-piste and ski touring, I’m currently working on a pre-recorded online ‘Essentials Talk’. Here’s a sneak- peek draft: a ‘staff talk version’ of the Essential Talk, featuring an accident Prevention Framework, which I’m making available free of charge for a couple of weeks on my YouTube channel.

If  you find it useful, please subscribe to this channel. There are lots of other cool vids in there too! Thanks again to Jérôme for the cover photo.

Safety is Freedom!