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: 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.

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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.

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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.

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Date of Observation: 01/09/2021
Name: Jared Berman & Jack Caprio

Zone: Northwest Mountains
Location: From Splains Gulch ascended the West face to the summit of Axtell. Skied South facing bowl before traveling back up S/SW ridge where we then skied the West face of Axtell back down to sleds
Aspect: North East, East, South-West, West
Elevation: 10,100ft – 12,500ft

Avalanches: None observed.

Weather: Broken clouds throughout the day and light winds from the NE. Several short periods of very light snowfall accumulating only trace amounts near and above treeline.

Snowpack:

The snowpack is still showing clear signs of instability on many aspects. However, collapsing and shooting cracks are only happening on specific terrain features and have started to become more stubborn.  Slabs are slowly faceting away but there are still many areas that hold a dangerous persistent slab structure.

While ascending a westerly aspect below treeline, we felt periodic collapsing in open meadows where we found soft slabs resting on top of depth hoar (12/10 interface). These collapses were almost always initiated by the third skier. HS on west aspects is shallow near and below treeline averaging about 75cm.

Near treeline on a SW aspect produced collapsing as well. One snowpit at this elevation/ aspect showed a 4F slab resting on top of Fist hard weak faceted snow. An Extended Column Test produced at ECTN21 at this location.

Moving around the compass to NE aspects we continued to experience several occasions of collapsing near and above treeline. Recent northerly winds did a number on start zones of the NE facing bowls of Axtell. These winds have created thin snow cover just below ridgetops that will surely weaken and become a problem at our next significant loading event.

We spent little time on east aspects, but experienced the most exciting results in these areas. A large collapse was observed with shooting cracks that ran about 30ft on a small East facing convexity at 10,000′. A snowpit dug adjacent to the collapse yielded our only propagating results of the day (ECTP 14). These failures were initiated on a thin MF crust sitting on top of the depth hoar (12/10 interface).

Continuing to a Southerly aspect, the skiing was surprisingly great with the exception of areas with a stiff sun crust on steeper slopes. Lower angled sunny slopes continued to ski great.

Bottomline: Many suspect slopes are weakening as slabs are faceting out. Obvious signs of instability are becoming rarer although they are still present.  W-N-E facing slopes below treeline slopes continue to maintain a persistent slab structure, while East seems to be the most concerning.

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