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.

 

GMT course through Rock Creek

CBAC 2020-21 Observations

Date of Observation: 02/26/2021
Name: Jack Caprio, Zach Kinler, Jared Berman

Zone: Northwest Mountains
Location: From Top of the World, we descended rock creek drainage to gothic campground
Aspect: North, North East, East, South East, South
Elevation: 9,600-11,600

Avalanches: Fresh wind slabs on a cross loaded alpine south aspect above Rustler Gulch (see photo).

An older, persistent slab avalanche on an east facing slope about 200 ft. above the east river valley bottom (see photo).

Weather: Westerly winds and overcast skies made for a cold sled ride in the morning. As the day went on, the clouds cleared and temps increased making for a very comfortable weather day.

Snowpack: We dug below treeline on a NE facing slope a couple hundred feet above the Gothic campground. We found a very stubborn persistent slab problem. At this pit site, the January interface sits 75 cm below the surface, with a large 1F hard slab resting on top. The 12/10 layer, which consists of large grained (6 mm chained) depth hoar, makes up the bottom 35 cms of the pack, and doesn’t seem to be showing any signs of improving. Snowpit tests did not produce any failures even after a couple aggressive swings from the shoulder after proper ECT tests (CTN, ECTX, ECTX). An aggressive shovel shear after our ECT tests did produce failure at the top of the 12/10 depth hoar layer. We did not receive any feedback from the snowpack such as cracking and collapsing while traveling in previously untraveled terrain.

The snow surface continues the near surface faceting process on shady aspects (currently .3-.5 mm NSF). On solar aspects, the surface consists of a 1-2 inch thick MF crust capping small grained facets. Everywhere we traveled above treeline (NE, E aspects), the snow surfaces were very beaten up due to recent winds, and hold perfect faceplanting conditions.

 

Photos:

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.

 

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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?).

 

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Anthracites

CBAC 2020-21 Observations

Date of Observation: 02/25/2021
Name: Jack Caprio

Zone: Northwest Mountains

Location: Anthracites
Aspect: North, North East, East
Elevation: 10k-11.5k

Avalanches: 1 D2 slab avalanche on a S facing slope in ‘the playground’ which I believe released due to a cornice chunk falling.
A couple small, wet loose avalanches on sunny slopes near rock bands that likely ran over the past couple days of warm weather.
Weather: Calm day. Sunny. Comfy temps
Snowpack: We mostly traveled on established skin tracks below tree line on N and NE aspects. HS ranged from 160-200 cms. Where I dug, the first concerning weak layer was >120cms below the surface. Snow pit tests produced no results at this site. No collapsing/ cracking all day.

Recent N winds produced noticeable scouring of surface snow in N facing exposed areas, and large cornice building/ loading on S facing start zones. In protected areas, small near surface facets continue to develop.

 

Photos:

The basement is still cluttered with junk

CBAC 2020-21 Observations

Date of Observation: 02/25/2021
Name: Zach Guy

Zone: Northwest Mountains
Location: West side of Ruby Range
Aspect: East, South East, South West, West, North West
Elevation: 9,700 – 11,700′

Avalanches: Nothing recent apart from a handful of very small wet loose sluffs. Plenty of previously undocumented large avalanches from the last widespread cycle (~February 13) at all elevations. We crossed a debris pile that was easily D3+ off of the southwest face of Ruby that only had about 6″ of snow on it, so I’m guessing it ran February 16. See photos.
Weather: Light westerly winds, no transport. Few clouds.
Snowpack: Targeted below treeline test pits hoping to see evidence that basal weak layers are gaining strength now that they have been buried by a deeper pack for a few weeks. Unfortunately, that doesn’t seem to be the case. The 12/10 layer is still large grained and angular, showing little signs of hardening or sintering. All test results propagated with sudden collapses, ranging from very easy to hard (ECTPV, ECTPMx2, ECTPH), 70 to 90 cm deep on depth hoar or large-grained facets on a crust. If there is anything improving the current structure, it is that the upper slab is faceting on shady aspects and meltwater is moving into the pack on sunny aspects, which should add some integrity when it re-freezes. I jumped on a few small, steep test slopes with no feedback, and we didn’t see any obvious signs of instability throughout the tour underfoot.

 

Photos:

Some good, some bad, all hot

CB Avalanche Center 2020-21 Observations

Date of Observation: 02/25/2021
Name: Wallace Cleaver

 

Zone: Northwest Mountains
Location: Slate
Aspect: North East
Elevation: ATL-BTL

 

Avalanches: Couple of wet slides that pulled out as point releases from below rocks on east tilt below treeline just above valley floor. Then all of the other ones documented in the area from a couple of days before. Of note, looked at the one in the palace and the avalanche had roared through some pretty dense trees causing some pause as to what true islands of safety really are.
Weather: Good, if you’re into sunny and warm. I prefer cloudy, snowy and cold though. Nuclear (or nucular as Dubyah used to say) in the valley floor.
Snowpack: NE aspect most of the way along the ridge had a serious windboard complete with that spooky hollow sound. Further down the ridge snow surface softened.
Below treeline soft with a couple clips of windcrust and easterlies had suncrurst. A lot of snow pulled out in the avalanches in the palace area, back to hitting some rocks toward the bottom, you know like back in December…

 

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:

More persistent slab action at Irwin

CBAC 2020-21 Observations

Date of Observation: 02/24/2021
Name: Zach Guy

 

Zone: Northwest Mountains
Location: Irwin Tenure
Aspect: South West
Elevation: NTL

 

Avalanches: Explosive triggered another large hard slab failing near the ground on a southwest aspect near treeline. The crown was 2 to 4 feet thick, failing on basal facets. HS-AB-R3-D2.5-O/G.
Also a noted a handful of smaller slabs in the Ruby Range that likely ran a few days ago during the wind loading event. They were relatively shallow slabs that broke in very steep, rocky terrain on easterly aspects above treeline (D1.5), likely on old layers as well.

 


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