We
triggered a moderate sized soft slab while ascending Forsnesvatnrenne and were
both taken for a terrifying ride of 200 vertical metres before coming to a stop
as a partial burial.
I’m writing
this down for myself really, as a learning tool so that I can analyse my
decision making process and better understand what mistakes were made.
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| The planned route for the day |
Decision
making process before and during the tour
Yesterday (30.12)
the mountains around Narvik received around 10cm of low density snow, which
fell under relatively calm conditions and was distributed quite evenly over all
aspects. At elevations lower than 800 metres the underlying snow was dominated
by a rain crust from a mild spell around Dec 27. At higher elevations the
underlying snow was primarily wind eroded snow, with isolated pockets of
windslab prevalent in sheltered areas.
With no
major snow fall in the past two weeks and relatively mild temperatures which
have promoted a strengthening of the snowpack, avalanche instability is
generally quite good at the moment. There hadn’t been any observed avalanche
action in the Narvik region for 10 days. The 10cm of snow which had fallen on Monday
did not constitute a significant danger in itself: it was a small snow event of
dry snow with a low water equivalent. The avalanche forecast for the day called
for a rating of 1, the first day of such a low rating since forecasting began
one month ago. The primary avalanche problem on the forecast was for dry slabs
above 400 metres on West through North aspects, with the anticipated weak layer
being the interface between the old rain crust and wind drifted snow.
Sometime
during the evening/ night the wind picked up such that by 10am there was a
strong breeze from the SW quarter.
I met up
with Bjarte at the base of the ski area, it was the first time we’d been on a
ski tour with each other, but we knew each other from frequent encounters on
Narvikfjellet where we both regularly do some skimo training. During the skin
up to 3de Toppen I was surprised to note that the new snow was still quite
evenly distributed around Linken and 2de Toppen. At this elevation of 1000 to
1200 metres the average depth of the new snow was 10cm.
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| Skinning past Skaret in the early morning twilight |
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| Surface conditions at Linken |
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| Skinning along the ridge between 2de Toppen and 3de Toppen |
From the
summit of 3de Toppen we skied in a WSW direction for 300 vertical metres to
wrap around the cliff bands which mark the start of the Partisanleden. The
skiing was superb, with this even distribution of “right side up“ snow
perfectly smoothing out all irregularities of the old snow surface. In terms of
snow stability it seemed that this aspect was very safe. Ski cuts on steeper
roll overs gave no results and no signs of instability were noted.
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| Skiing the SW facing slopes from 3de Toppen: even distribution of 10cm new snow |
We skinned
up to the entrance to the “Ramp” a steepish ski line (around 40⁰ in the upper
section) which descends 500 vertical metres in a NNE direction to
Forsnesvannet at 640m. The closer we got to the ridge the stronger the wind
was, coming from the SW at an estimated speed of around 15m/s. I was concerned
about windloading on the NE slope which we intended to ski. On closer
inspection I saw that the wind drifting was only an issue on the upper few
metres, below that the snow surface seemed mainly wind eroded and therefore
safer. Some tentative stomping on the rollover cleared the wind drift and I was
able to ski the upper section of the Ramp which was mainly wind eroded. Further
down there were a few isolated pockets of wind slab which were quite sensitive.
A few small, soft slabs (about 5-10 metres wide) released as I was skiing down,
but didn’t entrain any further snow. We used safety islands below rock outcrops
on the skiers left of the slope to avoid exposure from any snow which the other
might release. Once down lower on the slope where the angle was mellow the
skiing was great, with about 15cm of evenly distributed fresh snow.
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| At the top of the "Ramp" with strong winds from the SW building cornices to the lee NE |
When we
reached Forsnesvannet we discussed the instabilities we had found on the “Ramp”.
With the predominant wind direction being from the SW and the small pockets
which released on NE aspects I deemed the primary avalanche problem to be
isolated pockets of wind slab on North through East aspects, with small
avalanches releasing within the newly wind transported snow. Going off the even
distribution of snow on West through South aspects which we had encountered on
the descent from 3de Toppen I made the decision that the Forsnesvatnetrenne which
faces West was relatively safe.
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| Bjarte descending the "Ramp" |
On the
lower part of the ascent we encountered a few isolated areas of exposed crust
where the wind had stripped the new snow away, but mainly the snow surface was
soft, with about 10cm of ski penetration into the new snow. As we gained
altitude and entered the gully itself the snow remained soft. As I skinned
upwards I noticed that a few isolated sections had a density inversion within
the new snow, about 10cm of slightly denser snow on top of approximately 20cm
of lighter density. I was concerned about the weak interface between these
layers in the wind drifted snow, but these areas of “upside down” snow were
isolated and not particularly large. At an altitude of 1000 metres a section of
more wind buffed snow with only 1cm of ski penetration made me stop and
question aloud whether it would be better to switch over to bootpacking. But up
higher the snow looked softer. Bjarte took over the lead and continued breaking
trail upwards on skins.
At 12.30pm,
when we were at an altitude of 1100metres, Bjarte was about 10 vertical metres
above me and 10 metres off to the skinner’s left. I heard a sound which made me
look up and I immediately noticed an avalanche had released about 40 metres
directly above me and off to the skinners right. My initial instinct was to
scream to Bjarte that an avalanche had released, I was halfway through doing so
when I looked over and saw that he was already engulfed in a wave of snow. I
immediately tried to point my skis downhill and across the fall line in an
attempt to ski off to the side of the path. This effort was totally futile as
within a second I was myself overrun by the avalanche. The swimming instinct
came automatically but gave little result as I tumbled downhill in the snow, completely
out of control. After a few seconds I surfaced temporarily, gulped some air and
glanced Bjarte a few metres above me. I called out to him and he called back to
me. I continued trying to fight the force of the avalanche and attempted to
self-arrest, this slowed me down and Bjarte came crashing in to me. Bjarte
called out in pain as he crashed in to me, and I inexplicably appologised for
the collision. The final period of the slide was marginally more controlled:
with my feet facing downhill and my head above the snow I was able to “swim”
and maintain this position and realized that a complete burial was not very
likely. We came to a stop at an altitude of 900 metres, having been taken by
the avalanche 200 vertical metres over what I estimate to have taken about
20-30 seconds. When we stopped both of us were only partially buried up to our
thighs in snow that was very soft and still unconsolidated, so it was easy to
dig ourselves out. I was about 30 metres uphill from Bjarte. We called out to
each other and asked each other if we were injured. Bjarte was uninjured,
whilst I had a mildly sprained ankle, with the adrenaline coursing through my
veins I didn’t think that my ankle was particularly badly injured though, and I
knew that I’d be able to ski out.
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| Photo taken minutes after the slide, from 900 metres looking up the path. |
After a
quick bear hug we took stock of our gear. We had both lost one ski each, Bjarte
still had one of his ski poles and one of mine had come to a stop just beside
him, whilst Bjarte’s other pole had come to rest just beside me. Given that the
avalanche had already cleared the slide path and without significant hazard
from hangfire above we decided to hike up the debris to try to find our lost
skis. We found Bjarte’s ski 20 metres above where I had stopped, and continued
up to 1100 masl. without finding any trace of mine. As we were walking back
down through the debris I stepped on my completely buried ski by chance. By
this stage my ankle was significantly more painful, but still weight bearing.
We put our skis on and began skiing back to Narvik via Forsnesvatnet and the
usual summer hiking trail.
Mistakes
made. Lessons learnt
- Effect of localised wind patterns: The predominant SW winds which I had noted throughout the tour blinded me to the fact that the winds in these mountains are obviously highly localized, and wind loading is possible on the same aspects which are not wind affected on neighbouring mountains. In this case the wind loading in the upper extremity of the gully was not so obvious lower down, but I should have taken more note of the what the predominant wind direction had been in the period leading up to the tour, and shown more caution before exposing myself on a slide path which is prone to rapid wind loading from localised wind patterns.
- Human factor: A false sense of security on account of familiarity with the terrain. This particular route is one which I follow multiple times each winter, and this familiarity along with all the positive reinforcement inherent in having traveled over a slope in more stable conditions resulted in my having a somewhat blinkered view.
- Human factor: I was making constant observations of the weather and snow conditions on the outing, and taking note of them in a log book to submit to the avalanche forecasting program. But I was simultaneously concerned with moving quickly and efficiently through the mountains in order to complete the tour in daylight hours. We were both on light weight randonee skis and both share a common passion of “light and fast” travel through the mountains. This has been my standard approach to backcountry skiing for the past few years, and I have always rationalized that covering more terrain on any given outing gives me more feedback about snow and weather conditions across a variety of altitudes and aspects. Indeed I believe that travelling faster and over a larger area means that I get much more clues about potential instabilities than anyone of the “heavy and slow” breed of backcountry skiers who typically make only a single ascent/ descent on a tour. As I sit here now however part of me cannot help but question how much this focus on speed and efficiency might have caused me to neglect a more thorough investigation of the snowpack. To a mild degree I would admit to being a little rushed (in the same way that I am always a little “rushed”, preferring to either be moving, digging a pit or taking notes in my logbook than simply standing around). I guess this human error could be considered a variation of the so called “Lion Syndrome”: a rush for first tracks or summit fever.
- Over estimating my ability to deal with the avalanche problem of the day. Having made my observations of recent and current wind loading on a particular aspect and seen small slabs release on that same aspect, I felt that I had successfully nailed my analysis of what were the most dangerous slopes for the day. I was, in a word, over-confident about my cognitive ability in regards to the instabilities of the day.
The entire
experience was really a blessing and a curse- a terrifying but necessary
reminder for me to practice more humility in the mountains.
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