Final Fireside Chat of the Season! Tuesday, April 13 at 7 p.m.

CBAC Backcountry Notes

Our final Virtual Fireside Chat of the season is this Tuesday.  Dr. Erich Peitzsch, with the U.S.G.S., will be joining us from Glacier National Park, where he has been conducting research on wet avalanches, using drones to study the snowpack, avalanche fatality trends in the U.S., and more.  Join us at 7 p.m. on April 13th at this link: https://zoom.us/j/94179033141

Wet slab that ran during last weekend’s wet cycle on Avery Peak. 

Off season for avalanches

CBAC 2020-21 Observations

Date of Observation: 04/11/2021
Name: Zach Guy

Zone: Southeast Mountains
Location: Mt. Emmons
Aspect: North East, East
Elevation: Below treeline

Avalanches: Skier triggered a couple of shallow wet loose slides in very steep terrain. They didn’t run far or entrain more than the top few inches of mush.
Weather: Another beautiful day. Light winds below treeline. Temps in the 40’s. Clear skies.
Snowpack: Early afternoon tour on suspect below treeline slopes to assess the effects of last night’s warming trend. Ski cut wet sluffs were confined to very steep terrain and are still not entraining volume or gouging deeper than the top few inches. The snowpack is wet throughout with drainage to the ground now well established where we traveled. The snow was supportive to skis but boot pen is thigh deep.

 

Corn

CBAC 2020-21 Observations

Date of Observation: 04/10/2021
Name: Zach Guy and Eric Murrow

Zone: Northwest Mountains
Location: Upper Slate
Aspect: East, South East
Elevation: 9600 to 12500’

Avalanches: Nothing new.
Weather: Clear skies, mild temps, light ridgetop winds.
Snowpack: Nothing noteworthy. Good freeze overnight, surfaces started softening mid morning on easterly aspects. The top few inches were soft by noon. Found a few very steep or rocky terrain features late morning where the snowpack was weaker and mushier but ski cuts couldn’t get any wet sluffs moving. Snow now has dust on the surface and has developed some sun textures and runnels on sunnier aspects.

 

Photos:

Hunting for normal caution

CBAC 2020-21 Observations

Date of Observation: 04/09/2021
Name: Zach Guy and Zach Kinler

Zone: Southeast Mountains
Location: Copper Creek
Aspect: South East, South
Elevation: 9500 – 13000′

Avalanches: Nothing new today. Documented more D1 to D2.5 wet activity and cornice falls from the recent cycle; see photos of the most noteworthy slides. Also crossed a couple of the larger debris piles (D3.5+) I’ve come across from one of the February cycles; one knocked over a few mature trees.
Weather: Cool and breezy up high kept surfaces frozen at ridgetop. Clear skies.
Snowpack: Snowpack looks and feels like a May snowpack. No signs of instability or avalanche problems noted throughout the tour. Snow surfaces stayed frozen or thawed to ideal corn near and above treeline by 12:30 or so. The snowpack stayed mostly supportive to skis below treeline this afternoon, although some valley locations became punchy and unsupportive. Ski cuts on steep pitches where the snow was getting too sloppy didn’t produce anything.

 

Photos:

Normal Spring

CBAC 2020-21 Observations

Date of Observation: 04/08/2021
Name: Evan Ross

Zone: Northwest Mountains
Location: Ruby Range Near Irwin
Aspect: East, South East, South
Elevation: 10,500-12,600ft

Weather: Overcast sky became partly cloudy. Moderate westerly winds on upper elevation ridge lines. Light winds at lower elevations in the AM hours.
Snowpack: Normal spring, not much to say. We skied SE to E around noon. The top couple inches of the snowpack was nice and soft. On real steep slope angles you could just get that dirty 2-3″ of snow to start pushing down hill.

A few more from the recent wet cycle

CBAC 2020-21 Observations

Date of Observation: 04/08/2021
Name: Zach Kinler
Zone: SE/NW Mountains

Avalanches: Flew around the forecast area looking for notable avalanches from last weekend’s wet cycle not yet reported. I Estimated an additional15-20 large Wet Loose avalanches running out of steep terrain generally from E-S-W near and above treeline. Around 8 new Wet Slab avalanches were observed, all in the D2 range on a variety of steep, sunny slopes.

Snowpack: Turning brown.

 

 

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West Side Kebler Check In

CBAC 2020-21 Observations

Date of Observation: 04/07/2021
Name: Evan Ross

Zone: Northwest Mountains
Location: West Side Kebler and East Beckwith
Aspect:
Elevation: 9,000-10,500

Avalanches: Old avalanche activity was similar to other locations around our greater forecast area. Loose wet avalanches or rollerballs on all aspects except some high north. Some loose wet avalanches also gouged deeply into the snowpack or triggered wet slab avalanches. Only noticed a couple of proper wet slabs. No fresh avalanche activity from today.

Weather: Partly cloudy and winds helping keep the snow cool. Down low on the east side of Kebler pass the cold winds where holding a steady breeze. Down low on the west side of Kebler Pass the winds were calm.

Snowpack: Snow surfaces softened in the afternoon on all aspects below treeline. On northeast to east slopes around 10,000ft by east beckwith you could push small loose wet avalanches on steep terrain in the top 2″ of the snowpack. Not really much of a problem unless in bigger terrain maybe. Snowpack stayed supportable to boots on a variety of aspects down low. Dug into some NE to E aspects around 10,000ft near east beckwith with an HS in the 100 to 120 range. These couple of holes didn’t show any wet slab issues with water having already drained through the snowpack or the old depth hoar had at least become wet, and changing grain type. In the end, nothing too notable.

Punchy Cement Creek

CBAC 2020-21 Observations

Date of Observation: 04/06/2021
Name: Eric Murrow Zach Kinler

 

Zone: Southeast Mountains
Location: Cement Creek drainage
Aspect: East, South East, South, South West, West, North West
Elevation: 9,000′ – 11,400′

 

Avalanches: Several gouging loose avalanches below treeline on east and west aspects (see photos). Views into the upper elevation terrain of Brush and Cement Creeks revealed far less recent wet avalanche activity than areas closer to Crested Butte. Did not observe any obvious Wet Slab activity, even on terrain features that had the same characteristics of observed Wet Slab avalanches nearer to Crested Butte.
Weather: Mostly clear skies transitioning to partly cloudy by mid-day. Moderate westerly winds at ridgetop. Temperatures cooled throughout the day.
Snowpack: Traveling on snowmobiles in the AM was fairly straightforward off-trail with minimal trenching, but as the sun softened, but never fully broke down, surface crusts in the afternoon, snowmobiling off-trail became a challenging task with relentless trenching. Traveled off-trail at 11,100′ and produced a collapse that traveled about 150′ causing around an inch or so of vertical displacement in the snowpack (see photo). Boot penetration in this area was consistently to the ground (see photo). Ski penetration was mostly supportive on surface crusts.

Dug a quick profile on a northwest aspect at 10,800′ with a depth of 100cm (similar snowpack to large collapse) and found meltwater had descended around 50cm down stopping just short of the weak bottom half of the snowpack. The upper 50cm of the snowpack was composed of a 15cm surface crust with 35cm of 4f+ slab (with ice columns present) resting on weak, moist depth hoar. I performed an extended column test and it failed on isolation. The bottom half of the snowpack was moist but did not appear to have been flooded with meltwater yet. Surface crusts on all terrain traveled remained intact during the day; some softened on sunny aspects, but a thin “egg shell” remained which helped to limit Wet Loose avalanche potential. Shoulder and shady aspects below treeline continue to have enough slab structure in the upper snowpack to present future Wet Slab concerns once the meltwater faucet turns back on.

 

Photos:

More wet avalanches

CBAC 2020-21 Observations

Date of Observation: 04/06/2021
Name: Eric Murrow Ben Pritchett

 

Zone: Northwest Mountains
Location: Slate River corridor to Angel Pass area
Aspect: North, North East, East, South East, South, South West, West, North West
Elevation: 8,900′. – 11.600′

 

Avalanches: Numerous recent wet avalanches on northeast through east through south through west aspects. Many were small, but some were large, gouging Wet Loose avalanches. A couple of recent Wet Slabs were observed as well. Two fresh avalanches occurred today on northeast slopes of Schuylkill Ridge – a full-depth Wet Slab below treeline and a gouging long-running Wet Loose avalanche.
Weather: Very warm temperatures with thin high clouds passing by through early afternoon. Light winds from southwest below ridgetop.
Snowpack: Spring transition is well underway, with no dry snow observed on any snow surfaces. Near treeline on a north facing slope, we found about 2 inches of wet polycrystals on the snow surface, with a moist snowpack below that showed signs of yesterday’s meltwater percolating down around a foot and a half deep. The recent meltwater was frozen into widespread horizontal ice lens, likely around old melt-freeze crust buried in mid March. We dug a profile adjacent to a 48 hour old Wet Slab avalanche. The avalanche and our test profile were located on steep southeast-facing slopes with signs of light wind-loading. We measured a 230-300cm deep snowpack. The top of the crown was around 12,000′ and our profile was at a similar elevation to the middle portion of the slab that released (~11,700′). We found a pooled layer of meltwater 50cm below the snow surface that had spread horizontally through an old layer of large-grained facets below a melt-freeze crust. This layer corresponded to depth of the avalanche’s flanks. The slab broke deeper (up to ~100cm) near the crown, higher on the slope. Snowpack tests were not relevant as too much water had flowed through the snowpack since the avalanche released. Generally, the snowpack was pencil hard, with a few harder layers of frozen melt water. We couldn’t determine the hardness of the wetted weak layer since it was a frozen mixture of previously weak facets, an old crust, and newly frozen horizontal and vertical ice masses.

 

Photos: