Snow Conditions in the Buttermilks / Mt. Humphreys

SNOWPACK OBSERVATION
Mt Humphreys Approach / NE Couloir
Submission Info
Sunday, January 19, 2020 - 1:00pm
Red Flags: 
Whumphing noises, shooting cracks, or collapsing
Mt. Humphreys 37° 16' 13.8036" N, 118° 40' 25.6836" W
Snowpit Observations
More detailed information about the snowpack: 

A group of four skiers headed out to the Buttermilks to check out Mt Humphreys, with the objective of skiing the NE Couloir.  We had some information on the road conditions and snowpack from a friend who had ridden Basin Mountain the day before.

 

Buttermilk road is in decent shape, and one can drive quite a ways up with a high clearance vehicle.  There are a few tricky sections that are navigable with a bit of skill / bravery. We ended up parking at the point where McGee Creek crosses the road at about 6:45a, skinning by 7a.  We skinned up the road to the bench below Peaklet and started up the gulley near the creek.

 

While skinning in the lower sections of this gully, we experienced a disconcerting amount of whumphing.  Some digging into the snow showed about 6” fresh loose snow on top of a semi-supportive melt/freeze crust, on top of facets.  The weight of a skier was easily collapsing this structure. I have never heard whumphing like this on the eastside, so we took note.  Given the low angle of these slopes there was no immediate danger. We cautiously continued up the canyon to see how the snow in the higher elevation areas compared.

 

Once above 10,000’ the snowpack changed dramatically.  There was evidence of more surface wind effect and the crust that was collapsing down lower became quite robust.  We dug a hasty pit at the base of the bowl that leads to the upper moraine, just past Longley Lake. Snow depth in this location was 165cm.  We found 20cm of fresh snow on top of a knife hard layer that was at least 20-50cm in depth. We could get a probe through this layer, but it was a tremendous amount of work to try to shovel (required more force than my entire 180lb bodyweight).  We could not find evidence of any significant faceting in this location. The top 20cm was a bit wind effected but was well bonded to the knife hard layer. We continued up the bowl, using frequent probing to evaluate the strength of the underlying crust and hand shears to evaluate the windslab.

 

Reaching the upper moraine at about 12p, the group ate lunch and then headed over to the base of the NE Couloir to assess the snow.  With no loading from wind, sunlight, or significant temperature rise (it was near freezing), we determined that any potential slabs above us would require an additional trigger to move.  We skinned to the base of the rocks guarding the line, we noticed that there was a small exposed crack underneath the rocks on the climbers right, possibly part of the bergschrund. We crossed the snowbridge and got above this point.  The group anchored into the safest place possible while we dug a pit at about 12:45p.

 

Snow depth in this location was 245 cm, the deepest measurement I have made so far this season.  This pit looked much different from our pit at the base of the bowl. We were able to dig down to about 100cm without hitting the robust crust.  We found 30cm of fist/4F hard new snow on top of 50-70cm of near-same density 1F snow. Below these layers was knife hard snow/ice that was penetrable by the probe but difficult to shovel.  At the top of the new snow there was a density change that was worth checking out.

 

We performed an ECT to check how the top layer of snow was bonding to itself/the snow below it.  Repeating the test twice we saw ECTN 13 and ECTN 14. With no propagation, this looked like a fairly standard and safe profile for an alpine couloir given the recent snowfall.  The group decided to continue up the line and evaluate frequently with hand shears. Specifically, we were looking for any areas where the uppermost layer of the fresh snow grew denser, thicker, and less well bonded.  Booting conditions were variable and somewhat wallowy.

 

At 1:30p and about 300’ from the top of the couloir, the snow changed again.  The skier leading the bootpack started to encounter a hard, icy layer just below the new snow.  A hand shear in this location was able to move the top 15cm of snow, which was about 4F hard, with light/moderate force.  This layer broke on underlying loose snow (fist) on top of the icy crust (knife). The bonding was weak and there was not much holding things together above the hard crust.  Knowing that the slab was likely to get thicker near the ridgeline, the group decided to pull the plug. We figured the risk of triggering something above was not high, but that a stubborn windslab could break and cause serious problems this late in the afternoon on moderate consequence terrain.

 

We transitioned and skied back to the car, which was enjoyable and the right call.  The skiing conditions were quite good, although a bit wind impacted up high. Back to the car just before 4p.

Weather Observations
Blowing Snow: 
No
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Above Freezing
Wind Speed: 
Calm
Precipitation: 
None
Air temperature trend: 
Warming
Accumulation rate: 
None
More detailed information about the weather: 

Thin high clouds with the sun poking through frome time to time, temps warming from below freezing to just above freezing in the alpine

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