Collapsing with diminishing propagation

CBAC2020-21 Observations

Date of Observation: 01/04/2021
Name: Zach Guy

 

Zone: Northwest Mountains
Location: East Beckwith
Aspect: North, North East
Elevation: 9,600 – 11,500′

 

Avalanches: Nothing fresh, some D2 slab activity from last cycle.
Weather: Few clouds, light winds.
Snowpack: Less than an inch of new snow overnight preserved large grained surface hoar on the near and below treeline slopes that we visited. There was enough wind in exposed locations to destroy it.
Still getting semi-frequent collapses below treeline and a few collapses near treeline. The latter triggered by second person on skin track or from hard stomps. The collapses didn’t produce much for shooting cracks, but judging off of how far away trees were shaking, it seems that most radiated less than 20 to 30 feet. This is a notable improvement from collapsing observed earlier in the week. We didn’t travel much near anything steep enough to avalanche; the few small test slopes below treeline that we stomped on didn’t produce any results. See attached photo for a profile at 10,600 feet, which produced moderate propagating results (ECTP14) 50 cm deep on 2 mm, fist hard facets.

 

Photos:

Valley bottom, Slate Rive Valley in the inversion zone

CBAC2020-21 Observations

Date of Observation: 01/04/2021
Name: Eric Murrow

 

Zone: Southeast Mountains
Location: Below Climax Chutes
Aspect: North, North East, East
Elevation: 8,900′ – 9,300′

 

Avalanches: Nothing new to report
Weather: Mostly clear skies, reasonable air temps, but guessing a fair bit cooler than areas above the inversion.
Snowpack: Very short tour walking about near valley bottom below Climax Chutes at the low end of Slate River Valley. Checked on snowpack where I would expect slabs to facet the quickest on shaded slopes. Ski pen was generally 6 to 8 inches with snowpack depth around 70cm (a bit more than 2 feet). Walked through areas with no previous traffic and only produced one notable collapse but stomped/jumped in many places looking for one. Many slopes in this area had previously cracked/collapsed this past week, likely during the loading event around the 28th or 29th. Slab is soft but still present even in the inversion zone, no propagating test results – see photo (profile location did not show evidence of the previous collapse but ya never know).

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Elkton

CB Avalanche Center2020-21 Observations

Date of Observation: 01/03/2021
Name: Ben Pritchett

 

Zone: Northwest Mountains
Location: Elkton area
Aspect: South East, South, South West, West
Elevation: Near and Above Treeline

 

Avalanches: One tiny fresh wind slab off the Treasury to Galena ridge.
Weather: Ridgeline Wind Speed: 10-20 mph
Ridgeline Wind Direction: NW
Wind Loading: Previous
Temperature: 15 F
Sky Cover: Few
Weather Description: Clouds increased late morning through the afternoon. Light to moderate northwest winds.
Snowpack: Travelled over alpine south and southeast-facing slopes. Near treeline we travelled on east through south to west. No cracking or collapsing observed. A week ago on a similar route in the same terrain collapsing was common near treeline, but not above. Overnight northwest winds transported snow only near alpine ridgelines. Drifts were soft and posed no threat.

Photo caption: Northwest winds scoured windward alpine ridges and built soft fresh drifts. January 3, 2021.

 

Photos:

Large Remote Trigger

CB Avalanche Center2020-21 Observations

Date of Observation: 01/03/2021
Name: Joey Carpenter

 

Zone: Southeast Mountains
Location: Ridge btwx West Brush Creek and Deer Creek trail
Aspect: East, South East, South
Elevation: 9.5k-11.1k

 

Avalanches: R2D2 unintentional remote trigger. About 150 feet away from low angle ridgeline. E aspect. 150 ft wide running 1200 vert. Avg crown 65cm with deepest portions reaching 95cms. Slope angle averaged 37 degrees but propagated onto angles as low as 34 in start zone. Shattering cracks on 31-32 degree slopes adjacent to slide path. Ran on 1-2mm facet capped crust. 1F hardness throughout majority of slab w/ 4f nearing the top from recent transport. This avalanche was small relative to the path but I am certain was unsurvivable. It ran through countless trees, rocks and other terrain traps. It snapped trees 3-4.5inches in diameter. The debris pile was 255cm deep at the bottom of the path and set up very firm. The unaffected snow adjacent to the debris pile was 70cm of fist hard facets to the ground which I’m certain the debris wiped out in the path, essentially making the debris pile over 8 feet deep.
Weather: Weather was sunny and warm around 10am at WBC/Deer creek junction with calm winds. Thin clouds filtered in from the southwest throughout the morning and by 1300 had made it 7/8 coverage with S towards gunnison still holding onto blue skies. Weather got progressively more unsettled making recording crown stats difficult due to snow, cold temps and 10-15mph ridge-top winds. S1- snowfall began around 2pm accompanied by continued 10-15mph sustained winds from the SW. A brief period of S2 came through but settled back out to S1-.
Snowpack: Spx on BTL S&SE tilting slopes was thin and weak. Below ~10.5k there was little slab structure if any. Collapses propagated short distances with minor cracking. As I gained elevation, cracking began to propagate further with more substantial cracking shooting ~70 feet and notable slab structure from pole probes. In attached photos of crown “profile” you can see the P- facet capped crust that acted as the bed surface. There was another P- crust below this with ~5cm of facets above and below. The spx from the 30cm to the ground started at 1f and slowly degraded to about F hard basal facets. The slab was 1F+ to 4f-, bottom up. The unpredictable nature of the avalanche problems this year are terrifying. Please be careful out there friends.

 

Photos:

Hunting a Dragon

CB Avalanche Center2020-21 Observations

Date of Observation: 01/03/2021
Name: Ben Ammon

 

Zone: Southeast Mountains
Location: Far Side Coney’s
Aspect: North, North East, East, South East, South, South West, West
Elevation: Up to 11,000′

 

Avalanches: No new ones observed.
Weather: Mod winds NW
Morning sun had warmed S and SE surfaces
Snow flurries through the afternoon, no accumulation noted
Snowpack: Several collapses on untracked W-facing slopes BTL, none observed on the untracked E and NE BTL slopes we traveled on.
NE aspect at 10,800′ had HS of 85cm, but much greater if you looked for wind-loaded pockets right below the ridgeline along Coney’s.
ECTN24 down 50cm on 12/10 interface
PST 45/100 END down 50cm on 12/10 interface

 

Washington Gulch Crack

CB Avalanche Center2020-21 Observations

Date of Observation: 01/03/2021
Name: Andrew Breibart

 

Zone: Southeast Mountains
Location: Washington Gulch-Snodgrass T.H.
Aspect: West, North West
Elevation: BTL

 

Avalanches: NA. Didn’t hunt for slides on Gothic or Anthracite Mesa.
Weather: For the majority of the day, mostly cloudy and calm in our area.
Snowpack: cracking within 10 to 15 of new and old skin tracks on slopes <20 degrees. Cracks were less than 15 feet in length and not dendritic. Snow is not supportive as boot pen is about 14 inches. One whump was heard by group when moving from the road to the hillslope between the road and spruce fir forest.

 

Irwin Obs

CB Avalanche Center2020-21 Observations

Date of Observation: 01/01/2021
Name: Mike Barney

 

Zone: Northwest Mountains
Location: below Round Two, Irwin
Aspect: West
Elevation: 11,100′

 

Avalanches: SS-AS-R1-D1-O 50 to 60cm deep, 50′ wide, and ran 150′ triggered on Friday (1/1/2021)
Weather: Light to Mod southwest winds scattered clouds and around 17F.
Snowpack: NTL west aspect- 50 to 110cm HS, with a pencil to knife hard mid-pack layer and about 25cm of depth hoar on the ground. BTL west aspect sheltered from the wind- 80cm HS with 4F- mid-pack and about 25cm of depth hoar at the base.

 

Photos:

Faceted

CB Avalanche Center2020-21 Observations

Date of Observation: 01/03/2021

 

Zone: Northwest Mountains
Location: Anthracite Region
Aspect: North East
Elevation: 9200

Avalanches: No evidence of recent Avalanche Activity
Weather: Calm cold and Humid up high
Snowpack: Skiing 30 degrees or less and still whumphing in certain areas of the snowpack on the uphill .. our lovely persistant slab issue I suspect.

Widespread faceting and surface hoar:Faceted snow refers to snow grains within the snowpack that have transformed into larger, angular grains. Facets have weak bonds with neighboring snow grains.

If you don’t care about the consequences , get beyond yourself and consider the danger you put others in when you need to be rescued.

 

Photos:

Ruby Range

CBAC2020-21 Observations

Date of Observation: 01/02/2021
Name: Evan Ross

Zone: Northwest Mountains
Location: Ruby Range
Aspect: South East, South
Elevation: 10,700-12,600

Weather: Low clouds in the morning obscured the range, as those moved out a high cloud shield moved over for the mid day, with clearing in the afternoon. Increased winds were the main weather factor. Moderate speeds from the NW.

Snowpack: Snow surfaces that looked beautiful the last few days, had gotten affected by the recent increase in winds. In our case slopes that had the best SE to E tilt held soft snow surfaces, while some more southerly slopes had been blown back to old soft crusts or soft wind texture. Probably just due to the way the winds flowed through and around the terrain. In this area, there wasn’t much for new wind loading and the windward side of the terrain didn’t really have much snow for transport.

Several hand pits on S to SE facing slopes at upper elevations revealed no current avalanche problem. Never really found enough slab on the 12/10 curst to try and get a result. While skiing through areas that appeared to be more wind-loaded previously, also produced no results. Snowpack heights were measured were surprisingly shallow in the 40 to 60cm range on average. I wouldn’t have much trust in the snowpack structure observed during the next loading event. Those hand pits were on slope angles in the low 30-degree range. So the curst facet sandwich would be collapsible under new load with enough weight. Didn’t observe the thickness of those buried crusts on steeper slopes or the snowpack structure on the deeper looking sections of the slope.

Skier Triggered Slide on Axtel

CB Avalanche Center2020-21 Accidents, 2020-21 Observations

Date of Observation: 01/02/2021

Zone: Northwest Mountains
Location: First Bowl
Aspect: North, North East, East
Elevation: 11,350

Avalanches: 1 Skier Triggered D2 (red arrow). On our first lap (green arrow) we noticed no real signs of instability (no collapsing or cracking). Our stability tests were benign and our ski cuts produced no results. On our second lap while descending the ridge towards our intended chute, we noted that the snow seemed significantly more faceted and had a “trapdoor feel”. Skier 1 skied approx. 150ft into the chute before pulling out into the trees. Skier two followed and while making a final turn out of the chute to regroup with skier one, triggered the slide and was carried approx. 50ft downslope before skiing out of the path of the slab. The crown appeared to range between 1-2+ft and the debris ran approx. 700ft. The slab failed on October/November facets near or at the ground. There were no injuries. We are both incredibly thankful for the positive outcome.

Weather: Mix of sun & cloud. Light to moderate wind.
Snowpack: Unpredictable and frightening.
We also noticed surface hoar on every inch of terrain we traveled through, up to 5mm in size.

 

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