I skied in Rogers Pass last weekend Feb 4-5, finishing off an ARAC
course.
Synopsis
Large avalanches continue to run and surprise professional avalanche
forecasters, enforcing the lesson that events are unpredictable right
now but when they happen they come out huge.
Windslabs a meter or more thick and deeper instabilities are causing
avalanches to start at treeline and in the alpine. They run to the
valley bottom, with ski lines at lower elevations being hit. Travel in
any terrain exposed to large treeline or alpine slopes is not
recommended in the next while, even with the improving weather.
Snowpack tests and the feel of the snow under your skis and with
probing indicates a reasonably stable snowpack below treeline, but the
threat is from any open slopes above that can run down into the trees.
Of note is that the huge avalanche that occurred off Macdonald West
Shoulder on Saturday only cleaned out part of the start zone. Hectares
upon hectares of snow was left up there above the 2 m deep fracture
lines.
Terrain
Heavy trail breaking but awesome skiing in the trees. Poor skiing at
and above treeline. Recommended routes would be Grizzly Shoulder and
Bostock Creek tree lines.
Areas visited, on Saturday - Illecillewaet (part way up to the glacier
on climbers right, well away from large slopes); on Sunday - Grizzly
Shoulder. Max elevation gained was 1900 m on both days. Although other
skiers have been travelling through and even skiing in the lower parts
of avalanche paths, I decided against travelling beneath any runouts,
including. Most major paths in Connaught have not run and although the
Mousetrap in Asulkan got hit a week ago nobody knows how much snow is
left above there.
Avalanches
A size 2.5 ran naturally late last week into the trees (into ski lines)
in Dispatchers Bowl. On Saturday a size 4 triggered naturally and hit
the road, off Macdonald West Shoulder. Another size 3.5 was triggered
by artillery shortly after that, with all other artillery shots only
triggering small avalanches.
Snowpack
There was an average of about 2 meters of snow on the ground. The top
40 cm was unconsolidated and it got gradually denser up to the Xmas
crust, which is down 150 cm. Strengthening facets in the bottom 50 cm
of the pack. Weaknesses (compression test moderate and hard, sudden
planar shears) present down 40 cm and 75 cm but they were unreactive to
skis below treeline. In Grizzly shoulder a very thin weakening crust is
present down 100 cm (Jan 13 crust). Both this crust and Xmas crust were
unreactive to compression tests, but had hard sudden planar shears with
deep tap tests. Reports of skiers who ventured to treeline on Sunday
indicated "upside down" slabby surface snow layers (and poor skiing).
Weather
Snowing hard on Saturday, max temp near 0 degrees, calm. Snowing
lightly on Sunday, max temp about -1, moderate winds from the west
transporting lots of snow at ridgetops. Close to 25 cm snow
accumulation over the weekend.
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