Unstable layers in Sea to Sky corridor snowpack

[LeeLau]

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Message: 1
Date: Tue, 30 Dec 2008 09:41:34 -0800 (PST)
From: Public Mountain Conditions Report <mcr@informalex.org>
Subject: [MCR] Musical bumps
To: mcr@informalex.org
Message-ID: <1829.24.87.200.29.1230658894.squirrel@mail.sunbow l.ca>
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Went for a tour on the N side of Flute yesterday. A largely overcast day
with moderate SW winds and a few ?exquisite? sunny breaks in the
afternoon. The skiing in the upper alpine was quite wind affected and not
particularly great. As you approach tree line the surface conditions
improved along with the skiing.

Safe to say that we skied conservative lines and tip-toed our way around.
As reported by many the upper snowpack is quite interesting if not a
little unusual for the Coastal region. 15cm of low density (F) new snow
over a 15cm (4F) slab over 10cm of cold low density (F-) facets all
resting on the December 6th crust. Though this ?sandwich? made for
descent skiing it also made for very challenging uptracks as skies
continually collapse through to the December crust.

We experienced regular whumping especially in thin rocky areas and any
area peppered with small trees. Though there have been numerous reports
of Skier accidental and remotely triggered avalanches we were unable to
ski cut any features and saw little natural avalanche activity. Whistler/Blackcomb did produce numerous size 1-2 avalanches from ski
cutting on specific terrain features and from explosive control work

With forecasted precipitation and wind for the remainder of the week I
would expect the load and slab properties in the upper snowpack to
dramatically increase along with the hazard level. It is very likely that
the facet layer overlaying the December crust may be with us for a very
long time.



Keith Reid
ACMG/IFMGA Mountain Guide
Whistler BC
keith@reid.bc.ca


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Message: 2
Date: Tue, 30 Dec 2008 19:58:48 -0800
From: Public Mountain Conditions Report <mcr@informalex.org>
Subject: [MCR] Diamond Head/ Paul Ridge, South Coast
To: <mcr@informalex.org>
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Greetings West Coasters,



Considering the limitations of terrain that I would want to be on right now,
we opted to give bigger areas a miss today and do a short day tour up at
Diamond Head/Paul Ridge Area, thinking there could me more options for
skiing low angle terrain.



Just below the high point of Paul Ridge, the total snowpack depth was around
160 cm . We decided to have a look in the snow. About the sketchiest I have
ever seen it up there. At the site we dug our profile, we found 110 cm of
mostly unconsolidated snow sitting on 15 cm of ballbearing facets above the
hard crust that was buried in early Dec. We also found a (almost hidden)
3-5mm surface hoar layer down 75cm below the snow surface. The surface hoar
layer sheared easily with a 'pop', and the facet layer was so weak it was
almost falling out of the pit.



Even though the trail breaking was not difficult (skis only penetrated 25
cm), stepping out of the skis had us sinking almost up to our waists.



Heavy 'Whumfs' reverberating in the snowpack near ridgetop had me really
thinking about the terrain I wanted to be on. Sure enough, we were able to
trigger a LARGE size 2 avalanche (from jumping on safe terrain above the
slope, after I had someone watch from the side to make sure there was no
skiers/boarders below). It was at the top of the widest bowl off the north
side of Round Mountain (NE Side) for those that know the terrain. The
avalanche was 60-85 cm deep, 60 m wide, running 150m down almost to the
flats. Even though the failure plane was on the surface hoar, I think it
would have stepped down to the facets and crust if the terrain had been
bigger (wider and longer bowl), or the slab properties a bit stiffer.



There was plenty of blower pow to be had up there, but have to admit there
are many lines up there I wouldn't touch today.
Many groups heading into the Elfin Lakes hut for New Years. Good time to use
the designated 'winter route' with the orange stakes.



Keep in mind this weak snowpack is very unusual for the Coast, and is not
likely to heal quickly. Stick to low angle terrain, well away from avalanche
slopes above. If you are not really sure what this means, or have difficulty
holding back when you see those big powder lines, it might be best to enjoy
the in-bounds slopes for a while.



Brian Gould

Mountain Guide

[khyber.pass]

Thanks Lee.