Elkton Knob remotely triggered avalanche

CBAC2020-21 Observations

Date of Observation: 01/29/2021
Name: Eric Murrow

 

Zone: Northwest Mountains
Location: Elkton area
Aspect: East, South East
Elevation: 9,400′ – 11,200′

 

Avalanches: Remotely triggered a small, D1, avalanche on a steep east-facing slope at 11,100′ with previous drifting.
Weather: Mostly cloudy day, but with a few bits of sun and greenhousing. Winds picked up dramatically just after noon. Snow transport was visible across near and above treeline terrain throughout the Ruby Range for a few hours.
Snowpack: Experienced a few small, quiet collapses on drifty near treeline terrain. Dug a test profile adjacent to a remotely triggered avalanche. Slope that avalanched was around 38 degrees (measured from the side not on bed surface might be a bit steeper). Steep, previously drifted slopes remain a concern and seem sensitive to human triggering on the upper Persistent Slab interface.  This interface will likely be a real concern with the incoming storm. Descended a 25-degree southeast-facing slope at about 10,400′ feet that had dry surface snow….noticed a few rollerballs on a steep more southerly feature.

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January snow 2017-2021

CB Avalanche Center2020-21 Observations

Date of Observation: 01/29/2021
Name: Andrew Breibart

 

Zone: Southeast Mountains
Elevation: BTL

Weather: calm, near and above freezing. partly cloudy
Snowpack: sticky snow with snow clumping on skins.
See attached for snow depth and SWE comparison (2017-2021).

 

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Large Remotely Triggered Avalanche

CB Avalanche Center2020-21 Observations

Date of Observation: 01/29/2021

Zone: Northwest Mountains
Location: Purple Ridge
Aspect: East
Elevation: 11,600ft

Avalanches: Remotely triggered a large avalanche from a lower angled slope, connected to a steeper slope. After no signs to instability all day, finally found just the right spot to punch through the slab, into the weak layer, and get a collapse. No shooting cracks in the terrain where the collapse occurred, but within a few seconds the larger bowl started to avalanche. The avalanche ran on the slower side, no powder cloud. It was large in size and propagated widely. This slope has avalanche previously this season. The crown is estimated to have averaged about 40 to 45 cm, while the deepest part of the crown where it broke into a cornice was closer to 110 cm.

Weather: Mostly cloudy to overcast sky. Warm temps. Alpine winds picking up in the afternoon and transporting snow.

Snowpack: No other signs to instability. A few roller balls on steep S and SW aspects at lower elevations.

Watching for the persistent slab to wake up below treeline

CB Avalanche Center2020-21 Observations

Date of Observation: 01/29/2021
Name: Jared Berman and Zach Guy

Zone: Southeast Mountains
Location: Coon Basin / Climax chutes
Aspect: North East, South East
Elevation: 9200′ – 11300′

Avalanches: Nothing new
Weather: Warm temps all day. Snow showers early in the morning before skies opened up and the sun popped out for a while. The afternoon brought cloudy skies again and strong winds above treeline from the southwest with visible plumes off of the high peaks.
Snowpack: Traveling through wind-sheltered terrain near and below the treeline, we found slab structures ranging from 30-40cm on southeast and northeast aspects.

On southeast aspects, slabs from new snow were not as deep averaging about 30-35cm resting on top of a melt-freeze crust that varied in thickness depending on aspect and slope angle. One snowpit dug at 11,000′ on a southeast aspect and 28-degree slope revealed a Fist-4 Finger hard slab resting on top of a thick 4.5cm pencil hard crust. The crust is resting on top of weak facets 1mm in size. This was the only pit we dug that showed propagating results (ECTP21). We also got one collapse on a SE slope where the crust was thinner

On northeast aspects near treeline, the slab was slightly larger ranging from 35-40cm which is resting on top of 60cm of completely faceted snow. Slabs on these colder aspects are also Fist-4 Finger minus in hand hardness. Two test pits did not show propagating results. However, once we added additional load to the slab, extended column tests showed full propagation (see video below). We skied steeper terrain on northeast aspects with no signs of instability, but steered clear of possible crossloaded terrain.

As we moved lower in elevation below treeline on northeast aspects, the slab steadily became softer and softer until we reached 9500′ where snowpack structure is essentially all facets to the ground, with only 15cm of recent snow on top.

 


Photos:

Cream

CB Avalanche Center2020-21 Observations

Date of Observation: 01/28/2021
Name: Zach Guy

 

Zone: Northwest Mountains
Location: Washington Gulch
Aspect: South, South West
Elevation: N/ATL

 

Avalanches: Nothing new that wasn’t reported yesterday morning.
Weather: Thin overcast to broken, greenhousing. Light summit winds.
Snowpack: Rec skiing so we spent the day traveling in terrain where we didn’t expect to find instabilities: non-windloaded, south and southwest aspects. The 1/19 crust (over facets) is about 5cm thick and did not produce any signs of instability on steeper terrain. On flatter slopes, we got a couple of collapses where the crust was thinner. There’s about 45 cm slab up to 4F on the 1/19 layers.

 

Quiet Shallow Weak Cement Creek…kind of

CBAC2020-21 Observations

Date of Observation: 01/28/2021
Name: Eric Murrow

 

Zone: Southeast Mountains
Location: Cement Creek to Reno Divide for photo & glassing then tour on Hunter Hill
Aspect: North East, East, South East
Elevation: 9,000 – 11,800′

 

Avalanches: Observed a number of avalanches in the Cement and Brush Creek drainages…all from drifted terrain features. Two slabs in North Bowl on Cement Mountain D1.5s, D1.5 on very drifted NTL feature on Hunter Hill southeast aspect, good size D2 near White Mountain on east aspect ATL(looks to have failed near ground), 5 D2ish slides on east-facing slopes ATL in Twin Lakes drainage(long-distance view – some looked shallow, some looked deep failing)
Weather: Largely cloudy skies but often thin cloud cover with sun visible through clouds. Air temps were mild enough to moisten snow surfaces on south and southeast slopes below 11K. Winds were generally light – no observed transport off high terrain.
Snowpack: Traveling along Cement Creek corridor snow depths of 60cm near Deadmans TH at 9400′ and ~90cm at 10,800 near Hunter Hill’s east side. Skinning between 10,600′ and 11,800′ ski penetration was generally 8″ with support coming from windboard created by 1/13 wind event – occasionally in sheltered areas ski pen reached deeper than a foot or so. No signs of instability below treeline in sheltered areas (see test profile photo of east BTL slope). Wandering through a near treeline basin I was able to produce a few collapses with one being large, but not rumbling. I dug a profile on a slope adjacent to collapse with recent and previous drifting and found a poor looking structure. Two interfaces can produce avalanches – one below the recent storm snow (failing in facets below a windboard) and large-grained Depth Hoar near the ground (see photo). Applying this test profile to observed avalanches in the Brush and Cement Creek drainages it seems to fit well….shallow avalanches failing at the most recent storm interface and deep avalanches failing near the ground. The features that looked most concerning were near treeline or above treeline but immediately below ridges that allow for good loading and limit scouring…highest terrain (greater than ~12,500′ or so) often looked beat up by the wind. A deep, good looking leeward slope in these areas might be more or at least as concerning to similar slopes in Northwest Mountains/Ruby Range because weak layers look worse out east.

 

 

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Avy 2 Observation Tour-Washington Gulch

CB Avalanche Center2020-21 Observations

Date of Observation: 01/28/2021
Name: IAN MCDONALD

 

Zone: Southeast Mountains
Location: Washington Gulch – a little past Coney’s
Aspect: North East
Elevation: 10500 ft

 

Avalanches: None observed
Weather: Temperature: 30F
Sky: Broken
Wind: Calm
Precip: None
Snowpack: Our group dug 3 pits, height of snow ranged from 125-109cm.
Easy CT results: (3,8,9) SC
Moderate ECTP results: (10,11,16) SC
PST END (40/100,45/100, 65/100)
All results were on the same layer that ranged from 40-45cm depth from surface on the interface of the recent storm.
We observed 3 collapses on flat terrain during the day.
Skied terrain in the lower 30 degree range.

 

Photos:

Ruby Range Wind Loading

CBAC2020-21 Observations

Date of Observation: 01/27/2021
Name: Eric Murrow

 

Zone: Northwest Mountains
Location: Baldy south ridge up to southeast ridge down
Aspect: North, North East, East, South East, South, South West, West, North West
Elevation: 9,400 – 12,600

 

Avalanches: A handful of fresh avalanches with crowns looking sharp. D2 in the Martini on Richmond, D2 near Martini on an unsupported slope that triggered slope below, D2 near Ohbejoyful Peak, D2 Afley peak – all northeast and above treeline. A lil’ family of D1 Storm Slabs near Elkton below treeline on a steep east-facing feature from this past weekend (several inches of snow subduing crown and bed surface)
Weather: Mostly clear skies before noon then mostly cloudy in the PM over the Ruby Range – very light snowfall as well when clouds rolled in. Moderate westerly winds transported snow above treeline for most of the day (some near treeline but not as consistent). Loading looked reasonably efficient on many alpine peaks/ridges in the Ruby Range. Looking to the east towards White/White Rock massif noticed very little drifting (not sure if winds were relaxed or there is just less available snow for transport in the area)
Snowpack: I moved through a variety of southeast and easterly terrain features near and above treeline without signs of instability. Only jumped on smaller slopes or those close to 30 degrees or less. Minimal cracking on small drifted features even with active loading – snow felt a bit top-heavy. Was able to kick off a few human-sized cornice chunks on an actively loaded ESE alpine face without result – snow felt top-heavy but still soft and fist hard. Dug a profile on a drifted easterly-facing feature near treeline without propagating results, but the structure looks untrustworthy at the 1/19 interface (see photo). SE slopes in this area had a poor-looking facet/crust weak layer below that past week’s snow, but I wasn’t able to find more than 12″ of fist hard snow resting above so I did not perform any stability tests.

 

Photos:

 

Pow day

CB Avalanche Center2020-21 Observations

Date of Observation: 01/27/2021
Name: Steve Banks

 

Zone: Southeast Mountains
Location: Red Lady Glades
Aspect: South East, South
Elevation: 9,800-12,000

 

Avalanches: Noticed a small fresh looking windslab release from the center of RLB. D1 and maybe a bit older but the crown still looked fresh as compared to this mornings ski tracks. Looks like something significant in 4th bowl of Axtell, though my guess is cornice fall and/or windslab release and not persistent slab.
Weather: Sunny, cool and breezy up high. Snow surface stayed dry despite strong solar. Lots of snow moving near and above treeline. Temps stayed cold as new cloud layer came in after noon.
Snowpack: It’s getting supportive! HS roughly 135 cms as average around the terrain we traveled. More like 90 cms well below treeline. Could feel the old buried crusts in a couple spots, and the pack became quite weak at lower elevations.