Level 2 Class

CB Avalanche Center2016-17 Observations

Location: Crested Butte Area
Date of Observation: 01/23/2017
Name: Donny Roth
Subject: Level 2 Class
Aspect: North East
Elevation: 9,600’ to 10,800

Avalanches: photo is of a human triggered avalanche by another party – not my group. It happened at about 2PM at about 10,200’ in the trees to the skier’s right of the main Coney’s bowl.
Weather: Mostly cloudy to overcast.  No new snow.  Light NW winds throughout the day.  Temps in the teens and low 20s.  
Snowpack:

A couple natural avalanches (D2 – R1) on the east aspect below Long Lake.  One appeared to be a harder slab, on a wind loaded slope.  The other was thinner and looked to have more moisture – maybe failing due to radiation and gliding on a melt-freeze crust.
Our column tests were dramatic.  Compression test produced repeated CTM (12) SC on the 1/19 SH layer buried 35cm down. We had ECTP (8) SC.  Our PST result was PST 20/100 End.  The “slab” above the SH is only 4F-.  It does not feel like a slab.
At the end of the day another group shared photos of a skier triggered avalanche in Coney’s Glades.  The slide appears to be 10m wide and ran 50m or so.  The slope doesn’t look to be more than 35º.  It failed on the 1/19 SH.

A human triggered avalanche by another party – not my group. It happened at about 2PM at about 10,200’ in the trees to the skier’s right of the main Coney’s bowl.

coneys

Schuylkill Ridge

CB Avalanche Center2016-17 Observations

Location: Crested Butte Area
Date of Observation: 01/22/2017
Subject: Schuylkill Ridge
Aspect: North East, South East
Elevation: 9,500-11,400

Avalanches: Noticed several small pockets along the skin track that appeared to have slid naturally within the past 24 hours. These were very soft, storm slabs and were on isolated terrain features. Noticed a slightly larger, potentially skier-triggered soft slab (10-12″ crown) at the first main opening that the skin track traverses that was 20 feet wide and ran approximately 100 vertical feet; entraining enough snow to knock someone over or push them hard against a tree. As we were gaining the ridge on the more south-easterly portion of the climb, a pocket of snow between switchbacks on a slight convexity slumped and moved downslope an inch or so and a crack propogated 10 feet beyond the extent of our kick-turn. We descended the ridge feature at the northern edge of Birthday Bowl and had some sloughing on the buried surface hoar that was channeling deeper into the snowpack but not quite moving as a slab.
Weather: 8AM. Clear skies, little to no wind. A nice window between storm systems.
Snowpack: Still mostly unconsolidated storm snow from Friday. At lower elevations and on sun-exposed aspects, snow seems to be forming a more cohesive slab. At higher elevations and more shaded aspects 16+” of low-density storm snow is not bonding with the buried surface hoar. Seems like with a little more time, wind and/or snow load we will have some pretty touchy conditions.

CB Avalanche Center2016-17 Observations

Location: Cement Creek Area
Date of Observation: 01/22/2017
Name: ADB
Subject:
Aspect: South West, West
Elevation: BTL

Avalanches: just a few pin wheels off the skin tracks.
Weather: Clear skies and calm transitioned to scattered skies and calm. Temperature fell a little bit. This all occurred before 1PM.
Snowpack: Above the caves, west facing slopes had about 5 inches of fist hardness. No change in the snow while touring.

SW and S facing slopes developed a sun crust pretty quick this morning.

On a south west facing aspect, found one area near the aspen/blue spruce transition, where there was a 2 inch sun crust overlying 3 inches of fist hardness snow on top of another sun crust.

Tricky to find Surface Hoar

CB Avalanche Center2016-17 Observations

Location: Crested Butte Area
Date of Observation: 01/22/2017
Name: Evan Ross
Subject: Tricky to find Surface Hoar
Aspect: East, South West, West
Elevation: 9,500-10,700

Avalanches: Intently skier triggered several D1s on westerly aspects at 9,500ft. Slabs pulled back to slope angels of about 35 degrees. Propagated about 10 to 30 feet wide in small terrain above a drainage.

Good views of the peaks around the area. No other recent avalanche observations. Other then some previous loose snow avalanches from last week.
Weather: Clear skis east of Paradise Divide, became overcast in the afternoon. Calm winds with a few snow plums off random high peaks. Sun was warming snow surfaces.
Snowpack: On the January 19th surface hoar hunt. Surprisingly , mostly didn’t find it where expected. Multiple pits on 25-35 degree, easterly aspects had little for layers of concern in the upper snowpack. Test showed some failures within the storm snow, but not much for persistent grains at the 1/19 snow interface. Further expected to find it on some northeasterly rolls, but similar results as above. Some pits in the area had small NSF at the area, but these were random and isolated. This was open terrain to down valley winds. Maybe the SH had been blown away?

One pit on a more protected norther easterly aspect at 10,500ft had the surface hoar present. The SH wan’t visible in clean pit walls and column tests where needed to identify the layer. The snow above was still very soft and about 40 cm thick.

The only more obvious sings to instability was on collapsible crusts or facets on crusts. South easterly slopes had a thing and soft crust that was producing muffled collapses while traveling through the terrain. Small facets where below this crust. The most notable results where westerly slopes at 9,500ft that had small facets on a thin soft crust. Slopes over 35 degrees where reactive and some could be remote triggered up to 10′ away. These slabs where F+ hard and about 35-40cm thick.

Intentionally skier triggered soft slabs about 35 to 45 cm deep. failing on small facets above a soft crust. 1/19 interface.

IMG_2671

Intentionally skier triggered soft slabs about 35 to 45 cm deep. failing on small facets above a soft crust. 1/19 interface.

IMG_2112

Persistent Slabs BTL

CB Avalanche Center2016-17 Observations

Location: Paradise Divide Area
Date of Observation: 01/22/2017
Name: Nick Hill
Subject: Persistent Slabs BTL
Aspect: North East
Elevation: 10,000 ft

Avalanches: Saw 2 slabs release on the 1/19 SH layer (crowns about 50cm deep), on steeper slopes under convex rollovers. First was remote triggered by a skier about 15 ft away SS-A-R1-D1-I. Second slab either ran naturally, or was triggered at a significant distance from above. SS-N-R2-D1.5-I.

The second slide highlights how touchy the snow has already become. If we did trigger this slab, it was from a significant distance. If it ran naturally, it was likely from the solar effects this morning. Either way, the pack is unstable before this next storm moves in.
Weather: Calm sunny skies early, becoming overcast after noon.
Snowpack: Knee deep ski pen, waist deep boot pen. Did not notice obvious signs of instability while skinning. 1/19 SH layer found about 50 cm deep.

AIARE 2 Avy Course

CB Avalanche Center2016-17 Observations

Location: Crested Butte Area
Date of Observation: 01/11/2017
Name: Donny Roth
Subject: AIARE 2 Avy Course
Aspect: North, South, South West, West, North West
Elevation: 8,900’ to 9,900

Avalanches: On our descent, on a SW aspect at 9,300’ I intentionally ski cut a small convexity and managed produce a D1-R1 soft slab avalanche that ran on the crust. The crown was 15-cm deep, about 10-meters wide and started on a slope we measured at 43º. It ran about 50-meters down a 35º slope and the debris stopped at an aspen grove. We proceeded to attempt to duplicate this and got a few smaller results on slopes over 40º, but could not get anything to go on slopes in the 30s.
Weather: Broken skies with a period of high thin clouds and strong solar radiation. Light snow, starting at about 1430, no significant accumulation. Calm to light, SW winds. High temp of 0ºC recorded at 9,500’ at 1300.
Snowpack: New snow had settled to between 15 and 20 cm. We measured 30cm of new in this zone the previous day and estimated an HN24 of about 8cm, so settlement was obvious. Snow on solar aspects was becoming moist quickly in the afternoon. On S-SW aspects the new snow is on top of a 2cm, 1F melt-freeze crust. SH was evident on all aspects. A series of small column tests produced easy results on a SW aspect at 9,580’. CTE (4) SC @ the 1/19 SH later 17cm down. This same layer produced an ECTP (1) that propagated across the column. On the north aspect at this same elevation, the small column tests were similar and we got a PST (70/100) End. In both cases the above slab was still a soft slab, but the southwest aspect was moist snow.

AIARE 1 Avy Course

CB Avalanche Center2016-17 Observations

Location: Crested Butte Area
Date of Observation: 01/21/2017
Name: Tim Brown and Chris Pruden
Subject: AIARE 1 Avy Course
Aspect: North, South, West
Elevation: 8,900’ to 9,500′

Avalanches:
Weather: Overcast skies with a short period of high thin clouds and strong solar radiation, Light winds from SW, no Blowing Snow, Air Temp ~ 20*F, short period of S2 with 5cm total accumulation of rimed new snow.
Snowpack: Observed no new avalanches, cracking or collapsing. The 20cm of storm snow since Thursday was F hard and its bond to the old snow surface varied with aspect: poorly bonded to 5mm SH above a 2cm thick 1F hard crust on S aspects, well-bonded to the crust on W aspects (found no SH here), and semi-well-bonded to 3mm SH on a N aspect ~9500′.

A profile on a S aspect at 9,200′ with HS 150cm and PF 20cm revealed a 20cm thick, poorly-bonded soft slab of F hard storm snow over 5mm SH overlying a 2cm thick, 1F hard layer at the old snow interface (CTE SC, ECTP5). Compression tests showed Moderate SC results on 2 more interfaces, one just below the crust on a layer of 1mm FC and another down 34cm from surface. Neither of these interfaces showed a propensity for propagation in ECTs (both ECTN 15 and ECTN 17). We found 3 more buried crusts, but snowpack tests produced no alarming results on these or the 4F hard, 2mm moist basal facets.

Compression tests on the W and N aspects produced no sudden results.

The snow surface quickly warmed and formed a soft (4F hard), 2cm thick crust on S aspects that was quickly covered by an additional 5cm of new snow by 2pm.

CB Avalanche Center2016-17 Observations

Location: Cement Creek Area
Date of Observation: 01/21/2017
Name: ADB
Subject:
Aspect: North, North East
Elevation: BTL

Avalanches: No instabilities.
Weather: Broken skies and calm before 130PM
Snowpack: Less than 2 inches new snow/24 hours

Variability in SH distribution

CB Avalanche Center2016-17 Observations

Location: Kebler Pass Area
Date of Observation: 01/21/2017
Name: Evan Ross
Subject: Variability in SH distribution
Aspect: North, North East, South West
Elevation: 10,000ft to 11,000ft

Avalanches:
Weather: What happened to the storm, bummer. Snow showers on and off adding up to a few inches through the day. No wind down low and poor visibility of higher terrain. Thin clouds allowed for green housing on southerly slopes.
Snowpack: Traveled on below treeline terrain up to 11,000ft. The 1/19 surface hoar was both difficult to identify in pit walls and spatially variable. Surprisingly in one location at 11,000ft on a northerly slopes it wasn’t there. Test results where within the storm. 10,500ft northeasterly aspect the SH was small and difficult to identity. 40cm of recent storm snow was still very soft and had little cohesion. Southwest at 10,000ft the SH was about 2mm tall on top of a 1cm crust. Storm snow above was about 40cm and F+ hard with green housing helping with settlement. Snowmobile and ski tracks on good test slops looked to have no results or cracking.

tipping point

CB Avalanche Center2016-17 Observations

Location: Kebler Pass Area
Date of Observation: 01/20/2017
Name: jeff banks
Subject: tipping point
Aspect: East, West
Elevation: 9,200-12,200

Avalanches: SS-R3-D1.5/2? (poor visibility) W facing, 9,600ft, ~270ft wide opposite the R.L. skin track in gulley feature, anything steep ~40* had a distinct crown with ~10cm refill

SS-R1-D1.5/D2 (poor vis)~150ft wide E facing ~@ 11,300 E facing just right to skin trick ~38-40* ~10cm refill~ unknown amount of debris below in forest, still a good amount of “slumped” snow on the bed surface.

and a few small D1 pockets on Kebler road
Weather: S1-S2
West light to Mod
Snowpack: exposed areas 20-30cm drifts in skin track in short period of time
fresh cornice development

easy shears under HST ~30-35cm in FC/SH layer on crust. besides the 2 avalanches, , no propagation seen underfoot.