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HAT Off-Piste Snow Report, Savoie, 26 December 2012 - 2 January 2013
Snow forecast to continue - weather systems coming out of the West for the next week.
Large amounts of snow forecast between 12 pm Thursday to Midnight.
WEATHER FORECAST (as reported by Météo-France on 26 December)
Tonight: Temperatures falling to -2° at 1000 m, -6° at 2000 m and -11° at 3000 m. Strong W winds in the mountains.
Thursday 27th : Light snow will start to fall before daybreak, turning into continuous snowfall, snow/rain level 1500 m, dropping to 800 m on Thursday night. Significant accumulations of new snow. Winds turning W/NW high winds.
Friday 28th: Weather calming down. A few snow showers in the morning, becoming drier, but cloudy. Winds dropping and temperatures 1 or 2 degrees warmer Thursday.
Saturday 29th: Milder and sunny – high clouds. Wind turning SW.
Sunday 30th: Westerly winds. Light snow in the morning, followed by snow showers (snow/rain limit 1500 m, dropping to 800 m) in the afternoon.
Monday 31st: Bright spells, with temperatures at seasonal norm. W/NW weather system, becoming W/SW.
Tuesday 1st: Snow coming back in W/NW winds.
Wednesday 2nd/Thursday 3rd:
Calmer weather. NW weather system coming in. Drier with bright spells. Temperatures dropping. Cloudy frequent snow showers.
OFF-PISTE SNOW CONDITIONS
After some horrendous snow conditions off piste from the 23rd to the 25th, things are back to colder temperatures, fresh snow and some great skiing!
The avalanche risk remains at 3 today, possibly moving up to closer to a 4 tomorrow with the new snowfall forecast. The relatively warm temperatures of the previous days combined with dropping temperatures over the next few days, will help to stabilise the snowpack, with the colder snow bonding better to a stickier, wetter or now frozen crustier layers beneath.
During the unseasonably warm temperature of the 23 to 25 December, there was a big increase in instability as the melting and free water loosened the strength of the snowpack up to altitudes where the warming had a strong effect (about 2500 up to 2700m on South facing slopes).
Now that temperature are moving down closer to normal, the melt water is frozen and the humid snow has settled and stabilised. So the net effect of all that warming is now an increase in overall stability on the snowpack on slopes affected by the warming/melting.
Two primary sources of instability that will be increased with the new snowfalls:
1. Most importantly the weak layer of unconsolidated old snow (of depth hoar and faceted snow grains) from late November/early December on steep North’ish facing slopes from 2500 m and above, ESPECIALLY ON UNSKIED or little skied slopes of this nature (most accidents this season have occurred due to skiers triggering slab avalanches on these types of slopes).
2. There are or were a lot of cracks visible that expose the ground on slopes facing mainly South’ish (even North below 2000 metres). This is from the snow that fell on the bare ground from early December (as opposed to the snow from early December that fell on old snow above in 1.) These cracks, technically called “glide cracks” in snow science terms, open up a few cm each day then can release and turn into avalanches at just about any time of the day or night. Most of them don’t release and they don’t seem all that susceptible to triggering by people. BUT sometimes they do; so the best advice is not tempt fate by lingering underneath them for more than a couple of minutes e.g. I will traverse under these cracks to get from one place to another, but keep a very watchful eye on these “glide cracks”.
In sum, be cautious particularly above 2500 m, on steep gradiants, near ridges and mountain tops especially on North facing and little skied slopes due to the presence of isolated slabs - caused by the recent winds from the NW to SW - they run a risk of being triggered by the weight of one or several skiers.
We will be updating our blog as much as possible especially if conditions start to look unstable (or if I have some nice photos from a great ski!) on www.henrysavalanchetalk.com/blog also on twitter.com/HenryOff_Piste
TIP OF THE WEEK
Be careful on un-skied or little skied steep slopes facing North’ish above 2500 m
This is where the best snow is. However, due to the accidents that have occurred on these slopes recently, it’s clear that we all need to approach them with conscious decision-making (e.g. is there recent avalanche activity on similar slopes?; is your group prepared to ski that slope?) and risk management (choosing how you go down the slope if you decide to go there in order to minimize the risk of triggering an avalanche and the consequences if an avalanche occurs).
Ride Hard ! Ride Safe
Henry & the HAT Team
HAT Talks & On-snow courses this season: We’re setting up a programme for talks and on-snow courses for this season in Val d’Isère: for more info see our website www.henrysavalanchetalk.com, contact email@example.com or give us a call on 06 29 21 33 00