Zone: Crested Butte Backcountry
Date: 1/15/2021
Name:Â Jared Berman, Zach Guy
This week’s action consisted of extreme winds out of the northwest from Wednesday night (1/13) into Friday morning (1/15). Here’s the weekly summary showcasing how this event impacted our snowpack.
Date of Observation: 01/15/2021
Name: Evan Ross
Zone: Northwest Mountains
Location: Kebler to Scarps Ridge
Elevation: 9,000-12,000
Avalanches: Nothing new observed
Weather: Few clouds, with continued moderate to strong winds
Snowpack: Covered ground and moved around, just trying to get a better idea of conditions after the wind event. Mostly just traveling on roads and looking at the terrain. In the big picture, there was way more wind erosion on the snowpack, then any actual wind-loading. I really didn’t see much of any lens-shaped, pillowy, or well loaded looking terrain. I’m sure there was some form of loading, maybe NTL behind some tree fences or something. Though I wouldn’t say you could claim there is specific terrain with common characteristics holding fresh wind load, and instead, any fresh wind-loading looked more isolated to non-existent. Lots of wind-board and sastrugi out there unfortunately.
I also spent a brief period in lower Elk Creek. Some of the snow surfaces down low had some texture in the protected areas, but the snow surface was still soft and more capable of a facet sluff than a slab problem. The views I had up toward the start zones looked more like wind texture and not so much for lens-shaped loading.
Date of Observation: 01/15/2021
Name: Mark Robbins
Zone: Northwest Mountains
Location: anthracites
Avalanches: one small wind slab in 1/2 bowl of axtell, see photo. Some cracking on the ridge approaching top of AMR, see photo, and one settlement on the ridge as well.
Weather: windy. Still very windy.
Snowpack: we had the opportunity to sample a variety of snow conditions. Breaker windboard, supportive windboard, impenetrable windboard, breaker sastrugi, impenetrable sastrugi, wind stiffened, and even some merely wind fondled in the most protected trees left of friendly.
Photos:
Date of Observation: 01/14/2021
Zone: Northwest Mountains
Date of Observation: 01/13/2021
Name: Zach Kinler Evan Ross
Zone: Northwest Mountains
Aspect: East, South East
Elevation: 9,600′-11,600′
Avalanches: No recent natural activity. Intentionally ski triggered 2 harmless D1 loose dry avalanches on a steep pitch near valley bottom where the snowpack was thin and mostly faceted.
Weather: Warm start to the day with temps near freezing, strong solar gain and calm wind. By early afternoon, high clouds drifted in and wind increased. Light to moderate NW winds blew on ridge top as well as open east aspects below tree line.
Snowpack: Many of the lower elevation slopes near valley bottom facing E and SE aspects are shallow and unsupportive to skis. There is much variability in depth and structure here with mostly weak over weak. Moving from lower elevations to 11K, the snowpack depths double with more of a supportive midpack over weak, faceted snow near the ground. This terrain is right in the heart of our stubborn Persistent Slab problem. We experienced no signs of instability or recent avalanches however we managed this problem by focusing on consequences, skiing short to medium-sized slopes up to but not greater than 35 degrees that were planer, had clean run outs and lacked obvious trigger points such as trees, rocks, and convexities.
Date of Observation: 01/12/2021
Name: Evan Ross
Zone: Northwest Mountains
Aspect: West, North West
Elevation: 10,600-11,300
Weather: Clear sky in the morning, with high thin clouds moving in for the afternoon. Calm winds. Cold and inverted temps.
Snowpack: Headed back to some west and northwest terrain that I had traveled through 6 days ago. Back then we produced some, far-running, shooting cracks on the early December facets, and kept it conservative while traveling through the terrain. Today started off appearing quiet. A quick test pit showed a snowpack structure that wasn’t drastically different than 6 days ago. An ECTN result also started looking promising. HS at that site was about 80cm and the 4F to 1F- slab just barely couldn’t support boot pen, but obviously still supported skis nicely.
Once I got onto a few slopes we hadn’t previously traveled on, the collapsing snowpack and shooting cracks started to show up again. These cracks were not running as far as a week ago, but they still didn’t inspire confidence to get closer to bigger slopes. All the slopes I traveled through were relatively small and supported.
Date of Observation: 01/12/2021
Name: Zach Guy
Zone: Northwest Mountains
Location: Slate
Aspect: North East, East
Elevation: 9,000 to 11,400′
Avalanches: In a path that ran in mid-December, we skier triggered a long-running facet sluff that gouged to the ground. It ran about 1,000′ vertical feet and entrained about a foot of weak faceted snow, about D1.5 in size. Good communication from partners watching from ridgeline prevented this sluff from surprising the skier. It started off very small and slow but picked up quite a bit of speed and punch by the end.
Weather: Inverted temps, thin broken cloud cover in the afternoon, calm winds.
Snowpack: In the windsheltered terrain that we traveled in up to 11,000 feet, the slab has mostly faceted away. There is some residual 4F or 4F- faceted midpack. Test results on this structure were unreactive.
We tested a windloaded terrain feature near ridgetop (11,300 feet). The slab is noticeably denser (up to 1F midpack), and the test produced hard propagating results.
In some terrain that avalanched in mid-December, the snowpack is entirely fist hard, large grained facets. The structure is quite weak, and now capable of producing full-depth sluffs in steeper terrain.
Photos:
Date of Observation: 01/12/2021
Zone: Northwest Mountains
Location: Cool place
Aspect: North, North East
Elevation: 10,000-12,000
Avalanches: None
Weather: sunny, warm up high, calm
Snowpack: I don’t speak freaky deaky snow science but I do know this. The snowpack heading up to the ridge on a NE aspect was encouraging where it was deeper (120 cm) with a pretty stout “midpack.” Less encouraging when it got shallower and not so encouraging “midpack” (more like “midpunch”) due north 11,50-10,500 in areas that had not seen the sun. Like pole punchy with a smidge of resistance about 10 inches down and then no resistance to the ground. By the final pitch it was a facetfest. Swiss cheese? Spatial variability?
Photos:
Date of Observation: 01/11/2021
Name: Eric Murrow & Zach Kinler
Zone: Northwest Mountains
Location: Purple Ridge standard up track area
Aspect: North East, East, South East
Elevation: 9,600′ – 11,600′
Avalanches: nothing new to report
Weather: clear skies, nasty cold at valley bottom along the slate gave way to pleasant conditions just a few hundred feet above valley bottom and above. Very light winds near ridgetop with no drifting snow observed.
Snowpack: Ascended generally easterly terrain to ridgetop. This is a snow favored area around Crested Butte with the deepest snow accumulations in the forecast area. No signs of instability noted like collapsing or cracking. Very little traffic in this area since the 12/29 storm. Near treeline probing revealed a snowpack around about 120cm or so deep with a very dense slab resting on top of the basal weak layer. See profile for a look at the snowpack in sheltered terrain in this area. The slab is dense, up to pencil hard BUT the weak layer remains uninspiring with minimal signs of improvement like rounding or increased hardness. Stability tests only confirmed the stubborn nature of human triggered avalanches, you would need to find a thinner spot in the slab to get a result, but if you did, sure would be an ugly avalanche.
Went to have a look at the large, natural avalanche from 12/29 on Purple Ridge to test adjacent slopes and identify how deeply it failed. Probing through part of the bed surface revealed that this avalanche failed very near the ground. Even with 20cm of refilled snow on the bed surface, the snowpack was generally only 30 to 50 cms deep in total. Tests adjacent to this slide produced an ECTP 16 on the same interface just 20 to 30cm above the ground. Probing hangfire showed 150 – 200cm right below ridgetop quickly tapering to 130cm-ish 30 to 50 feet below ridgetop. The slab in this drifted area was mostly pencil hard helping to insulate the weak layer from the weight of a person, but I was surprised at how poor the weak layer continues to look (4finger hard) and I still remain uninspired to test the waters on big, drifted terrain features. Definitely stubborn to trigger but not confidence-building assessments. Bed surface of this previous avalanche path consists of lower density, small-grained facets sitting on a slick, crusty bed surface….a recipe for certain avalanches once it is reloaded by a significant storm.
Photos:
Date of Observation: 01/11/2021
Name: Zach Guy
Zone: Northwest Mountains
Location: Schuylkill Ridge
Aspect: North East, East
Elevation: N/BTL
Avalanches: Minor sluffing
Weather: Strong inversion. Mostly clear skies. Calm winds.
Snowpack: Rec skiing – traveled on mostly existing skin tracks or terrain that avalanched in mid-December and saw no signs of instability until reaching flat terrain at valley bottom, where we got one large collapse that produced a shooting crack 150′ long. Widespread weak layers on the surface: surface hoar decreases in size and distribution at higher elevations. Near surface facets are widespread. The snowpack in terrain that avalanched earlier in December is noticeably weaker (often trapdoor skiing on larger grained, fist hard facets) and is set up to be a repeat offender whenever we get another slab-forming event.
Photos:
