Snodgrass study pit

CB Avalanche Center2020-21 Observations

Zone: Southeast Mountains

Location: E facing knoll on Snodgrass

Date of Observation: 11/26/2020

Name: Jack Caprio

Subject: Snodgrass

Aspect: East

Elevation: 10,000

Avalanches: None observed

Weather: Scattered clouds, sun coming in and out. Temps around 20’s. Light winds less than 10 mph out of the south.

Snowpack: I tested the snowpack on an east facing aspect below treeline. I found thin melt freeze crust at depths of 20 cm and 15 cm with F hard facets above and below. Sitting on the bottom of the pack are 15 cm of 1-1.5 mm facets

No exciting propagating results in stability tests. However, both the fractures on CT and ECT collapsed on the interface of old faceted snow and the melt freeze crust at 15cm. This weak layer crust has the potential to initiate, but it is unlikely to propagate.

Photos:

 

NE powder SW sun crusts

CB Avalanche Center2020-21 Observations

Zone: Northwest Mountains

Location: Poverty Gulch

Date of Observation: 11/28/2020

Name: Travis Colbert

 

Subject: NE powder SW sun crusts

Aspect: North East, South West

Elevation: 9,200-11,600

Avalanches:

Very slow moving sloughs (top 20cm) on 36-38 shaded slopes. Very slow moving shallow slough/slab (10cm sun crust) on 32-34 degree sunny slope.

 

Weather: Blue skies & very little wind. Single digits in the morning, warming to the lower 20s by afternoon.

Snowpack: HS 90-95cm on shaded NE slopes; upper 20cm unconsolidated new snow sitting on a soft crust. HS much lower (did not measure, but maybe 20cm) on sunny SW slopes; but compacted and supportable with 8-10cm soft sun on the surface.

Photos:

Poverty Gulch

CBAC2020-21 Observations

Zone: Northwest Mountains
Location: Poverty Gulch
Date of Observation: 11/28/2020
Name: Evan Ross

Subject: Poverty Gulch
Aspect: North East, East
Elevation: 9,500-12,000

Weather: Another beautiful weather day. Light winds at ridgeline and high temps felt like they reached into the upper 20’s to near freezing.

Snowpack: It’s sad to see the cold clear nights faceting away the upper snowpack. The mid-pack still had good support for now, and the combination of the weak upper snowpack and stronger mid-pack is keeping the skiing good. Unfortunately we are watching or snowpack go its typical Continental direction.

Focusing on the now, and not what we’re going to be dealing with later. Normal caution feels spot on. Or, good group travel techniques, while keeping an open eye out for something isolated that doesn’t look or feel right. It’s getting hard to call a specific or particular increased hazard to manage, but rather the standard general awareness and normal caution seem most appropriate.

There were several old sluffs in the terrain, and fresh skier triggered sluffs in steep terrain. These were to small to pose much of a hazard, but highlight the weakening snowpack all the way up to upper elevations.

Weak layer smorgasbord

CBAC2020-21 Observations

Zone: Southeast Mountains

Location: Snodgrass

Date of Observation: 11/28/2020

Name: Zach Guy

Subject: Weak layer smorgasbord

Aspect: North, North East

Elevation: 9400′ – 11100′

Avalanches: Skier triggered several loose dry (facet sluffs) on steep, shaded aspects, D1 in size, entraining the upper half of the snowpack.
Investigated the reported skier triggered slab from yesterday. The slab was about 10 feet wide, 18″ thick, on a very steep, convex rock feature. It was a soft slab that appeared to fail on 1.5mm faceted grains on the ground. It entrained weak, faceted snow as it ran downhill. SS-ASc-R1-D1-O/G

Weather: Clear, calm winds, mild and inverted temps.

Snowpack: Widespread weak layer growth on all aspects and elevations! 2 to 4 mm surface hoar is developing on shady aspects up to about 10,000′, and pockety above that. Near-surface faceting in the recent snow is rampant on all aspects. The near surface facets are above a melt-freeze crust on SE-S-SW aspects. The entire snowpack is getting noticeably weaker in the past few days, becoming unsupportive and faceted throughout. We did not observe any signs of instability other than facet sluffing today. The current snowpack will become a problematic weak layer when/if we get a significant load.

 

Photos:

 

Slides on Snodgrass NE Lines

CB Avalanche Center2020-21 Observations

Zone: Southeast Mountains
Location: 2nd Bowl
Date of Observation: 11/26/2020

Subject: Slides on Snodgrass NE Lines
Aspect: North East
Elevation: ~11k

Avalanches: D1.5, hard slab, 18 inch crown, interface between facets at the ground and newer 4F stiffness snow:

Dropping into 2nd bowl to check out coverage, stayed on the rail skier’s Right. Suspect terrain evaluated before skiing was exactly what slide: small convex rollovers formed over rock shelves in the top 50 feet of the line. Used a ski cut on top of one of these terrain features to get the entirety of the snowpack–which was about 18 inches–to fracture. Ran about 500 feet, picking up lots of speed and snow. The crown broke and propagated over pretty obviously terrain features, stopping at the concave gut of the line.

We made another ski cut just to clear the remaining hangfire and got a smaller slide to go, running only about 200 and entraining much less snow. D1.

Weather: Slight flurries, alternating sun and high cloud cover, 25-30F, no wind.

Snowpack: Ranging from a few inches on South faces to 2.5 feet on NE lines, from the ridge down to Gothic Road. F-4F slab sitting on about an inch of 2-3mm facets.

 

Reno Divide

CBAC2020-21 Observations

Zone: Southeast Mountains

Location: Cement Creek Road to Reno Divide area

Date of Observation: 11/26/2020

Name: Eric Murrow

Subject: Reno Divide

Aspect: North East, East, South East, South, South West, West

Elevation: 9,000 – 12,250′

Avalanches:

none observed. Visibility was not great but viewed several north and northeast alpine features without evidence of recent activity.

Weather: Low ceiling with clouds clipping the tops of peaks in the Elks that were greater than 13k. Winds were very light while traversing a 12,000′ ridgeline. Air temps felt cold in valley bottoms, but pleasant at 12k. I could feel the cold air still sitting in valley bottom on return trip home at 330pm. Clouds increased through noon with light intermittent snowfall and slowly decreased through 4 pm. No accumulations in this area.

Snowpack: Shady terrain near valley bottoms felt weak, although grain size was small, the faceting process appears to be happening in recent days.

In Reno Divide area, at 11,000′, new snow from two days ago was around 6 or 7 inches, with snow height in shady, protected areas around 55cm, a bit shy of 2 feet. Wind redistribution from the past few days was less than expected at 12k.  Closer to 13k and above looked wind effected with modest stripping of windward aspects. Traveled across a 12k ridgeline with mostly easterly terrain and struggled to find much recent Wind Slab formation, very isolated and generally soft at this elevation. Windward areas of this 12k ridge had soft snow still available for transport if the winds ramped up.

Northeast features above 11,600′ had dry 1-2mm facets at the ground like much of the CBAC forecast area. Stability tests did not inspire confidence with ECTP moderate scores, but stomping on and above small, drifty features produced no collapses or cracking.

Southerly slopes around 12k had thin, weak crusts at the surface with faceted grains below. Without any significant incoming storm on the horizon, this structure may change before it is tested by a new load.

Skied easterly terrain with about 50cm of snow that was reasonably supportive and provided nice turns.

Photos:

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Upper Slate

CBAC2020-21 Observations

Zone: Northwest Mountains
Location: Purple Ridge
Date of Observation: 11/26/2020
Name: Evan Ross

Subject: Upper Slate
Aspect: East
Elevation: 12,000-9,600

Weather: Clouds decreased to partly cloudy during the mid-day, then started increasing to mostly cloudy again in the afternoon. Mild temps. Clam winds down low. Moderate wind at ridgeline with periods of snow saltation close to the ground. No plumes off the high peaks. Up to an inch of new snow today baby! Keeping it soft, better than nothing.

Snowpack: Traveled in this same area a couple of days ago. Not much change. The old wind-drifts at ridgeline were hard and didn’t give any signs to instability. Today’s new snow had formed some soft few inch drifts right near ridgeline.

Backcountry riders continue to step out and ride more and more terrain features. With conditions going mostly quiet I suspect we will see few observations come in.

Bit of this bit of that

CBAC2020-21 Observations

Zone: Northwest Mountains

Location: Poverty Gulch – around easterly side of Mineral Point

Date of Observation: 11/25/2020

Name: Eric Murrow Zach Kinler

Subject: Bit of this bit of that

Aspect: North East, East, South East, South

Elevation: 9,500 – 11,650

Avalanches:

Several small (D1) wind slabs observed on east and northeast above treeline slopes. One below ridge top, others mid feature on small inset portions of the feature.

Weather: Cold temps at valley bottom gave way to warm, pleasant. conditions on sunny terrain features. Light winds near and below treeline; some blowing snow and loading above treeline on to southeasterly slopes.

Snowpack: Sunny slopes had several inches of moist snow resting on supportive crusts. The snow on warm features wetted to old crust and refroze to old surface once the sun left the terrain below treeline.

East facing slopes remain dry below and near treeline in this area. Evidence of some wind redistribution near treeline, but really no hazard from Wind Slabs in areas traveled. We were able to produce some minor cracking on the most suspect drifts, but nothing more.

Stomped around on several small drifts behind tree fences on northerly terrain and got one localized collapse on an obvious wind whale but it didn’t produce any cracks. Probing showed weak faceted snow at the ground, but outside the wind whale there just wasn’t much of a slab.

Photos:

Small sluffs and slabs at upper elevations from the past 48hr’s

CB Avalanche Center2020-21 Observations

Zone: Northwest Mountains
Location: Upper Crystal Watershed
Date of Observation: 11/25/2020
Name: Evan Ross

Subject: Small sluffs and slabs at upper elevations from the past 48hr’s
Aspect: North, East
Elevation: 11,000-12,000

Avalanches: Maybe 20’ish small avalanches at upper elevations, mostly releasing from wind-loading, but a couple coming out of rock bands. A few from today, others were slightly older. Mostly sluffs, or maybe small cornice chucks coming down. Few small crowns. There could have been more crowns that were either too small to see, or had blown back over. These avalanches were observed on west,  north and east aspects, with easterly having the most activity.

Weather: Clear, mild temps. Moderate ridgetop winds with light transport. Mostly calm conditions at lower elevations.

Snowpack: North 11-12,000ft: Skied a couple different laps and a couple different skin tracks. HS was generally in the 60 to 80cm range. We traveled on new snow over old wind-board, to a general 70cm snowpack over a thin layer of dry facets, and through many transitions from the supportive slab into shallow a less supportive snowpack. All and all the snowpack was mostly quiet outside of a couple of small collapses. Those collapses didn’t seem to collapse big parts of the slope. The layer of facets at the ground is fairly thin and maybe there was too much ground roughness.

Easterly 11-12,000ft: Great riding conditions on east with the new snow over a supportive snowpack. Tilt a little SE and the snow-surface was becoming moist. We climbed into the start-zone of an easterly bowl right below a ridge. Sections of the bowl were stripped of the new snow by NW winds. Other sections had more of a cross-loading pattern. We moved through a few thick cross-loaded drifts on 35-degree slopes. Those drifts were thick and not giving us any feedback to instability.

All and all, we found good stability and some lovely turns.

Also noticed several ski tracks of folks skiing some large bowls on the northerly side of Baldy, and on both easterly and northeasterly bowls off Purple Ridge. Looked like some folks got some good turns.

 

Stubborn wind slabs

CBAC2020-21 Observations

Zone: Northwest Mountains

Location: Augusta

Date of Observation: 11/25/2020

Name: Zach Guy

 

Subject: Stubborn wind slabs

Aspect: East, South East, South

Elevation: to 12,500′

Avalanches:

Two small natural windslabs on easterly aspects near and above treeline that likely ran Tuesday morning. A dozen or so small loose dry avalanches on steep northerly terrain in more sheltered basins, likely similar timing. All D1s.

Weather: Clear, mild temps. Moderate ridgetop winds with light transport, a brief period of moderate transport this afternoon.

Snowpack: About 4″ to 6″ of settled storm snow, generally on a stout melt-freeze crust on the sunnier aspects that we traveled on. The snow saw a fair amount of redistribution from northwest winds at near and above treeline elevations – drifts up to 18″ thick. Wind slabs were quite stubborn today; minimal feedback from stomping on test slopes. Got one crack after undercutting a steep, wind-loaded feature and then stomping on it from above (See photo). Skied terrain up to 38* with no instabilities.

Photos: