Observations

Date of Observation: 12/15/2022
Name: Evan Ross

Zone: Southeast Mountains
Route Description: Mt Emmons. N to E. 9,000ft to 11,400ft.

Observed avalanche activity: Yes
Avalanches: Lots of old avalanche activity in the terrain, but nothing new or notable that doesn’t fit the mold.

Weather: Mostly cloudy, calm wind, cold.

Snowpack: Climbing up through the terrain the snowpack transitioned from weak and shallow, to deep and stubborn. Somewhere in the middle, there was a narrow band where the persistent slab avalanche problem may have been reactive. Only a few collapse with notable effort. A couple of those shook trees but didn’t produce on the nearby steep slopes. Overall the snowpack structure remains poor and has just become less reactive or stubborn.

9,600ft. NE aspect, 35-degree slope. HS 60cm. ECTN. The mid-pack slab was 4F over the F November Facets. Facets are developing throughout this snowpack and the mid-pack slab was losing its ability to propagate a collapse. Near this pit, I found some recently formed wind drifts that added structure and made that specific snowpack reactive.

11,000ft. ENE aspect, 30-degree slope. HS 100cm. ECTX, CT21 SC on the November facets. Here the mid-pack slab was 1F .8mm rounded grains over the F 2.5mm faceted grains. Poor snowpack structure. No amount of jumping or punching ski boots to the weak layer was producing a collapse.

Somewhere between those two locations, it felt like there should be a sweet spot where the persistent slab avalanche problem would be more reactive. I couldn’t put my finger on where exactly that is.

11,200ft. NNE aspect. This slope had previously avalanched. Below the bed surface, there was about 10cm of well-developed facets. Above the bed surface, there was 25 to 30cm of new snow that was faceting and losing strength.

Photos:

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Date of Observation: 12/15/2022
Name: Benjamin Schmatz

Zone: Southeast Mountains
Route Description: RMBL Snow Study Plot in parking lot in front of Dining Hall

Observed avalanche activity: No

Weather: Light Snow, overcast, and cold ~15deg

Snowpack: At this location we do not see any old snow problems. The first few storms of the season melted out and did not stick. The bottom layer here was created by the 11/28 storm cycle and has built up since then. Relatively stable considering the lack of faceted snow at the bottom. It was difficult to even discern a layer delineation in the snow pack, but we determined that grain size and hardness deserved a boundary designation. ECTX. no result from an extended column test.

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5755

Date of Observation: 12/15/2022
Name: Turner G

Zone: Southeast Mountains
Route Description: Seen from 135

Observed avalanche activity: Yes
Avalanches: M face of whetstone. Natural early this am. Finally cleared up again to kind of get a photo.
Weather: Windy, cold, socked in.
Snowpack:

Photos:

5754

Date of Observation: 12/15/2022
Name: Travis Colbert

Zone: Southeast Mountains
Route Description: Standard ascent through the forest to the top of First Bowl. Descended skier’s right edge of the bowl. NE aspect; 9,600-10,800 feet.

Observed avalanche activity: No

Weather: Brisk and overcast with light, intermittent snow and temps in the single digits to low teens. Light to moderate W & NW winds at the ridgetop.

Snowpack: Plenty of fresh windslabs have formed along the ridgetop and in the open terrain. The persistent slab seems to be getting stiffer and more stubborn to trigger. It seems like if triggered, there is a good probability of wide propagation and hard slabs. All of the old crowns have filled in with new wind-driven snow. Best turns were down low in the protected, gladed terrain.

Photos:

5753

Date of Observation: 12/14/2022
Name: Evan Ross Zach Kinler

Zone: Northwest Mountains
Route Description: Slate River Valley. NE 9,000-10,800.

Observed avalanche activity: Yes
Avalanches: A recent large avalanche in the Climax Chutes that likely ran last night. At 10am the crown was blown back in while the avalanche debris looked fresh. This was a cross-loaded terrain feature below 10,800ft.

Weather: Cold. Generally, calm wind except for a few gusts down in the open valley. Mostly cloudy. A few flakes, but no real accumulation.

Snowpack: Obvious signs of instability were rare. A few collapses with notable effort and a couple of localized shooting cracks.

HS varied between about 90cm to 135cm on average. We targeted two test profiles on NE aspects, one with an HS of 90cm at 10,000ft and one with an HS of 125cm at 10,700ft. In both locations the snowpack structure was poor. Thick slabs to 1F or P, over F to F+ November Facets. The change in grain size at the interface was about 1.5mm. ECT results were ECTP22 in the lower location and ECTX at the upper location where it took several full-strength whacks after the standard test to get through the slab and produce a failure.

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5751

Date of Observation: 12/14/2022
Name: Zach Guy

Zone: Southeast Mountains
Route Description: Viewed from Mt. CB

Observed avalanche activity: Yes
Avalanches: One fresh-looking D2 persistent slab off of the north side of Barcelona Bowl, likely ran yesterday. Saw a couple of small ones near Meridian Lake that might be older, or maybe they just got a bit drifted in if they ran yesterday. Poor visibility of anything beyond the donut hole.
Snowpack: Evidence of shallow wind slab formation (up to 8″ thick, 4F) in cross drifted near treeline slopes.

Photos:

5749

Date of Observation: 12/14/2022
Name: Billy Barr

Zone: Southeast Mountains
Route Description: Gothic townsite

Observed avalanche activity: No

Weather: Little weather here with just a trace of snow each of the past 2 days but no warming as yesterday’s high ws 14F and today’s low 10 with a steady wind bringing more blowing snow. No sign of sun and snowpack down to 23½”.

5748

Date of Observation: 12/13/2022
Name: Troy Hendrick

Zone: Northwest Mountains
Route Description: Coneys up to Anthracite Mesa ridge, setting far skiers left skinner instead of traditional semi-bushwacker skinner. We roped into the crown of the slide a few days earlier to get a close up as part of a course. Dug pits on due NE leeward slopes, kicked small cornices on the ridge and skied The Nose.

Observed avalanche activity: Yes
Avalanches: Nose Stake D1.5 which ran 12/10 and is listed infra in a separate observation.
Weather: Light snow, cold, somewhat foggy later, overcast
Snowpack: Roped into a D1.5 avy crown just skier’s left of The Nose Stake. The pocket ripped on 12/10. We tried to kick off hangfire as we roped in with no results. Skied Coneys on The Nose. Very good skiing, if a little windboard bounce. Dug pit on the far skier’s left skinner. 105 cm snowpack, NE aspect, 30 degree pitch 10,700′. Trashpile of 2mm depth hoar facets from ground up to 25 cm. This is the obvious layer where the 12/10 D1.5 failed. 28-30 cm is a crust. 4f up to fist through rest of snowpack to surface. Temp gradient across 1m is -8 Celsius. This was sortof surprising given the super cold air temps. We would expect further faceting but this snowpack is managing to stay rather warm.

Photos:

5747

The 12.2-12.9 Weekly Snowpack Summary is here. Two storm cycles kickstarted widespread natural avalanching. The week ended with high pressure moving in and excellent riding on lower angled terrain.

CBAC Weekly Summary December 2-9 (1)-compressed

Date of Observation: 12/13/2022
Name: Eric Murrow

Zone: Northwest Mountains
Route Description: Kebler Pass road to Horse Ranch Park then up Cliff Creek route to Beckwith Pass.

Observed avalanche activity: No
Avalanches: non observed, visibility obscured views of the east end of East Beckwith or any other steep terrain in the area.
Weather: Overcast skies, moderate winds blowing west to east down the Kebler Pass corridor, light snowfall from 11am to 3pm. Storm totals ranged from 9 to 12 inches from Kebler Pass to Beckwith Pass. Snowfall rates during the day were light enough to be offset by the settlement in the storm snow already on the ground.
Snowpack: Near Beckwith Pass, I measured 11.5″of storm snow with .75″ of snow water equivalent. I dug a couple of profiles below treeline and found a snowpack that ranged from 100 to 130cm. Snowpack tests showed moderate propagating potential on basal facets. Given that the slab at this location (see photo) was nearly pencil hard, I think the .75″ of water in the storm snow had made the Persistent Slab problem more sensitive to the weight of a person, but not nearly enough to produce natural activity outside of highly drifted leeward features at upper elevations. I didn’t experience any collapsing while snowmobiling or while stomping through the slab directly above suspect test slopes. Due to slab thickness, around 90cm, and with a hardness near Pencil at the bottom of the slab, I would not really anticipate signs of instability in sheltered terrain until I found a trigger point. I also did not find any buried surface hoar beneath the storm snow in several suspect locations. I was able to produce cracking up to 15 feet in fresh, shallow drifts on lee features below treeline.

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