Gothic Wet Slide

CB Avalanche Center 2020-21 Observations

Date of Observation: 03/03/2021

Zone: Southeast Mountains
Location: South face of Gothic Mtn.
Aspect: South
Elevation: 12,000-11,000

Avalanches: Skier triggered shallow, slow moving, long running wet slide running on a hard crust 12 inches deep.

Weather: Sunny with little to no wind. Temps reaching upper 30’sF.

Sand Box

CB Avalanche Center 2020-21 Observations

Date of Observation: 03/02/2021
Name: Evan Ross Zach Kinler

Zone: Southeast Mountains
Location: Slopes near CB
Aspect: North East
Elevation: 8,900-9,500

Weather: Blue bird and sunny. Snow surfaces stayed cold where we traveled.

Snowpack: The sandbox is trying to come back, but thankfully it’s just the surface snow for now. The top 20cm of the snowpack was faceted and weak. That made for some nice soft turns, slippery skinning, and fuel for small loose snow avalanches.

We were hunting for a below treeline, NE facing snowpack, with a total snowpack height in the 100-120cm range. That’s just what we found and the end goal was to get more data about the current persistent slab problem. The PSa structure across an individual slope was variable. Sometimes complexly weak, and sometimes a 1F mid-pack above the 12/10 facets. So we could sum up that avalanche problem as “Isolated” in the terrain.

For test results. We observed no signs of instability while traveling on slopes in the mid-30 degree range. We tried doing the standing jump thing, hitting some other jumps, taking a ski off and punching… quiet. We dug two pits at locations with 1F mid-pack over the lower layers of concern. ECTX and ECTP 22 on 12/10 interface. We would estimate the sensitivity to fit “Stubborn” more than “unreactive”. Put a bunch of snowmobiles or skiers on the same slope and there are a couple of spots that they may just produce a large slab avalanche.

Skier triggered slides on snodgrass

CB Avalanche Center 2020-21 Observations

Date of Observation: 03/02/2021

Zone: Southeast Mountains
Location: 3rd Bowl
Aspect: North East
Elevation: 10,800

Avalanches: Triggered a couple small sloughs and a small slab approximately 15 ft wide 8” deep crown in the more northerly trees knocking over a skier.
Weather: Pretty rapid warming through the morning

Anthracite Mesa near Washington Gulch TH

CBAC 2020-21 Observations

Date of Observation: 03/01/2021
Name: Eric Murrow

 

Zone: Southeast Mountains
Location:
Aspect: North East, East, South East, South
Elevation: 9,400′ – 10,600′

 

Avalanches: nothing new observed
Weather: Clear skies, moderate temperatures, and light winds.
Snowpack: Traveled through an area that has a snowpack depth near the median for the Crested Butte area – not as deep as areas further west/north and not as shallow as terrain further east. Snow surfaces on the south half of the compass became moist by early afternoon, but no wet snow concerns developed in this area. Melt/freeze crusts 4 to 6cm thick on sunny features, but still slightly soft not fully supporting skis without breaking. Ice columns from warm period at the end of last week pushed up to 8 inches below the surface – liquid water will need to move about an additional 30cm down, or more, to reach weak interfaces. Dug a test profile on an east aspect testing Persistent Slab problem and did not get results in ECT, but PST results continue to fail well before 50% of cut length. The persistent Slab problem appears very stubborn on this below treeline terrain.

 

Photos:

War Zone in the SE

CB Avalanche Center 2020-21 Observations

Date of Observation: 02/26/2021

Zone: Southeast Mountains
Location: Cement Drainage
Aspect: North East, East, South East, South, South West
Elevation: 10,300′-12,100′

Avalanches: Everywhere in sight, especially E facing terrain. D1-D2+ on virtually any alpine feature which took on drifting recently, along with some unusual NTL/BTL features which normally wouldn’t be suspect. Most of the recent avalanches we observed today have already been reported, but not all of them. Basically, if you looked below a cornice on a leeward aspect, it went big. Sorry, no pictures.
Weather: Windy. Steady and swirling winds, mainly out of the W/SW at 10-20 mph all day. Probably was gusting to 30+ at higher elevations based on the flagging we observed off many of the surrounding peaks. Air temp wasn’t as cold as we expected this morning. My car read 18F at TH at around 9am. Apart from the consistent and gusty strong winds, air temp seemed pretty mild for the majority of the day.
Snowpack: Mainly traveled on W/NW BTL and NTL, but also had a quick transition on a southerly aspect NTL. Snowpack depth was relatively uniform. Pole probes went to ground at 110cm-130cm. On the ridgeline, where the wind has stripped the majority of the season’s snowpack, depth was around 30cm. Snow was supportive on all aspects we traveled, with a ski pen of around 3-6.” Once we stepped off our equipment though, boot pen went to ground with full weight. For the most part, the skiing was surfy and supportive. However, variable crusts exist on the sunny aspects and wind-affected terrain, of course.

 

Keepin it Snoddy

CBAC 2020-21 Observations

Date of Observation: 02/26/2021
Name: Zach Guy

Zone: Southeast Mountains
Location: Snodgrass
Aspect: North East, South East
Elevation: 9500 – 11,000′

Avalanches: Shallow facet sluffing in steep terrain
Weather: Moderate winds, minimal snow transport. Cool temps. Few clouds.
Snowpack: Quick look at snow surfaces below treeline ahead of the next storm. Melt-freeze crusts start on east aspects (1 to 2 cm thick) and get thicker wrapping to due south (at least 8 cm thick). There were small grained facets below the crust, but not above. Northerly tilts have widespread small-grained near-surface facets, and some protected areas have small surface hoar growth.
One pit produced propagating results on all of the prominent weak layers in the lower half of the snowpack, but only after additional loading steps (about 35 hits). The 1/19 facets were down 80 cm and the 12/10 depth hoar down 110 cm, with a 1F midpack.
We rode several steep pitches where the snowpack is wind protected and uniform with no signs of instability.

 

Photos:

Mountain Snowpack-Cooperative Snow Survey Program for NRCS

CB Avalanche Center 2020-21 Observations

Date of Observation: 02/26/2021
Name: Andrew Breibart

 

Zone: Southeast Mountains
Location: Red Lady Glades and CB Nordic Trail
Elevation: BTL

Weather: Keystone snow course/Red Lady Glades: obstructed skies and strong winds. colder temperatures before 9AM
Crested Butte snow course/CB Nordic Magic Meadows yurt: few clouds and light winds with moderate gusts and warming temperatures between 10 AM and 12PM.
Snowpack: Keystone snow course: 2.54 cm (1 inch) melt-freeze crust on the surface. Snow depth ranged between 68 and 112 cm (27 and 44 inches) across 41 meter (135 foot) transect with 5 samples.
Crested Butte snow course: depth ranged between 86 and 107 cm (34 and 42 inches) across N to S transect of 122 meters (400 feet) and W to E transect of 74 meters (244 feet). melt freeze crust 61 cm (24 inches) below surface (1/19 or 2/5 interface?).

 

Photos:

Upper Cement Creek Drainage

CBAC 2020-21 Observations

Date of Observation: 02/25/2021
Name: Eric Murrow & Ben Pritchett

 

Zone: Southeast Mountains
Location: Cement Creek drainage to head of valley near Tilton
Aspect: North, North East, East, South East, South, South West, West, North West
Elevation: 9,000 – 11,600′

 

Avalanches: Observed a good number of previously unreported avalanches from the last significant loading event around February 13th or later from wind-loading. Below treeline there were a few natural avalanches on east through north features. Near and above treeline previous avalanche activity was observed on west, northwest, north, northeast, east, southeast, south and southwest aspects. Wind-loading was able to overload weak structures around the compass at upper elevations. Many of these avalanches were in terrain features that were frequent runners, but several of the avalanches were in paths that have not run in many years. Continue to expect the unexpected.
Weather: Clear skies, light winds in valley bottom, and mild temperatures. No snow transport observed
Snowpack: We observed a mostly quiet snowpack. Two small collapses, one that produced localized cracks. Lower down in the valley, the snowpack remains mostly faceted, without well-developed slabs. In these areas, if a storm delivers a rapid load of new snow wide spread avalanching like what was seen in mid February could be expected again. For now, it’s just weak, poor structure, with little avalanche concern except where slabs are built in wind-drifted features. Further up in the valley, from around 10,500′ upwards, the mid-pack slabs are much more mature, thicker, and dangerous if triggered. Basal weak layers connect across terrain features. Propagation potential remains high, and potential avalanche size remains large. The upper snowpack is a mix of very stiff wind board and wind slab, as well as numerous melt freeze crusts, with thin layers of facets laminated in between. The upper snowpack slabs are generally stiff. The weak layers are fairly discontinuous. Together that adds to a picture where triggering has grown stubborn in this area; that said, the consequences remain scary. We chose to travel under some paths that avalanche recently and had not refilled, and chose to alter our route to avoid some paths that had not yet run.

 

Photos:

Cement Mountain loop

CB Avalanche Center 2020-21 Observations

Date of Observation: 02/23/2021
Name: Jack Caprio and Eric Murrow

Zone: Southeast Mountains
Location: North Cement Mountain
Aspect: North, North East, East, West, North West
Elevation: 9,000′-12,200

 

Avalanches: Observed a number of avalanches on Cement Mountain of varying ages from the past month.  Included images for avalanches that likely failed around the Feb 13/14 time frame.  Most of these avalanches failed on drifted features with two below treeline on non-drifted slopes.  Looking around leeward features in Southeast Mountains did not see any other recent avalanches.  While driving pavement in afternoon, I spotted a couple very small loose avalanche on Gothic Mountain coming out of steep, rocky southerly features.
Weather: A cold early morning in the canyon quickly gave way to warm, sunny weather. Above treeline, W and NW winds blew at consistent moderate speeds with high gusts.

Snowpack:  Toured up and over Cement Mountain.  This is a relatively shallow snowpack area as it is in the Southeast Mountains and receives less snow volume than other areas in Southeast Mountains due to its location.

Below 10k, the snowpack consisted of generally 80 cms of thin crust/ facet combos. When HS was less than around 80 cm, ski pen was to the ground. As we increased in elevation to about 10K-ish, HS increased above 80 cms to around 100cm and the snowpack thankfully began to support the weight of a skier while breaking trail. We didn’t get any alarming signs of instability as we were making our way up through the trees on N aspects below treeline.

As we got near and above treeline, we continued to see W and N winds transport snow onto leeward start zones. A snowpit test on a slightly windloaded, NE-facing aspect near treeline produced moderate propagating results. We did get one large rumbling collapse while traveling on ridgeline, adjacent to the NE facing start zones. The collapse did not produce any cracks but it was loud enough to hear over the blustering winds. Much of the avalanche paths we traveled above had already slid during the last 3 weeks. Most of the bed surfaces had not refilled enough to slide again. We chose not to ski any of the slopes that had previously avalanched because of the low quality of skiing, not necessarily avalanche hazard.  Briefly touched a few below treeline sunny slopes that were moist but not wet enough to cause Wet Loose concerns due to winds keeping surfaces relatively cool.

 

Photos:

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