Very small wind slabs and cornice falls

CB Avalanche Center2015-16 Observations

Location: Crested Butte Area
Date of Observation: 12/17/2015
Name: Evan Ross
Subject: Very small wind slabs and cornice falls
Aspect: East, South East
Elevation: 11,700-12,300

Avalanches: Several very small natural wind slabs and cornice falls on Mount Emmons and Red Coon.
Weather: Blowing snow for several hours around mid day, then quieting down in the late afternoon. Partly cloudy sky with clouds obscuring the upper slate river valley.
Snowpack:

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Quick Kebler NTL/BTL Snowpack

CB Avalanche Center2015-16 Observations

Location: Kebler Pass Area
Date of Observation: 12/16/2015
Name: Evan Ross
Subject: Quick Kebler NTL/BTL Snowpack
Aspect: West
Elevation: 10,600, 11,400

11,400ft NTL, west aspect. 4F Wind hardened recent storm snow over 4F 1.5-2mm facet. No results in CT tests and minor cracking with explosives. Slope had seen previous traffic before storm.

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11,600ft, west aspect, BTL. About 10″ resent storm snow over large fist hard facets. No slab, no results other then sluffing in steep terrain.

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Wind slab on Gothic

CB Avalanche Center2015-16 Observations

Location: Crested Butte Area
Date of Observation: 12/16/2015
Name: Zach Guy and Jimmy Buchanan
Subject: Wind slabs on Gothic
Aspect: South, South West
Elevation: 10,000 -12,500 feet


Avalanches: On a S/SW facing slope above treeline, we skier triggered a wind slab up to 10″ thick (4F) that ran on the melt-freeze crust interface. It was up to 250 feet wide, and ran 1,600 vertical feet. It entrained a significant amount of snow and gouged through the melt-freeze crust into facets halfway down the path. Given the terrain trap it was in, it would have buried or severely injured someone. SS-ASc-R2-D1.5-I.
We also noted several D1 to 1.5-ish looking debris piles in the Ruby Range on east aspects. Too far away to tell if these were loose or slab avalanches; presumably naturals.
Weather: Few increased to Scattered clouds. Light southwest wind with no transport. Cold temps.
Snowpack: 2″ of settle storm snow below treeline, over supportive melt-freeze crusts or dirt on S, SE aspects. Facets below the crust. The new snow was noticeably denser and more cohesive than yesterday. Above treeline, the new snow was drifted from 3″ to 10″ deep from northerly loading patterns, cracking under foot. SE, S, and SW appeared to catch most of the recent wind loading, as well as windloading events from previous storms. NW and NE aspects were bare, with plants/rocks/facets showing. E aspects showed a mix.

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Snodgrass Study Plot

CB Avalanche Center2015-16 Observations

Location: Crested Butte Area
Date of Observation: 12/15/2015
Name: Jimmy Buchanan
Subject: Snodgrass Study Plot
Aspect: North East
Elevation: 9,800

Avalanches:
Weather: See profile. No observed precipitation.
Snowpack: See profile. Mostly faceted snowpack with a harder layer of faceting/windpacked rounds.

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Anthracite Range

CB Avalanche Center2015-16 Observations

Location: Kebler Pass Area
Date of Observation: 12/15/2015
Name: Evan Ross, Zach Guy
Subject: Anthracite Range
Aspect: North, East, South
Elevation: 10,000-11,500

Avalanches: A few very small soft slabs that appeared to be about 4″ deep, failing within the storm snow, on a SSE near ridgeline. The crowns had started filling back in and estimations were tough. Several, small skier triggered sluffs in steep terrain.
Weather: Overcast sky. Snow showers were steady in the morning before tapering by 11am with a few short, heavy bursts in the afternoon. At ridgeline winds were westerly to northwesterly. Before noon they were light with moderate gusts, then increasing around 2:30 and becoming more steady at moderate speeds. Cold temps.
Snowpack: By 3pm, storm snow accumulations where in the 14-17″ of low density snow around 11,000ft.  Most of the accumulations came last night and early this morning.  Near ridgeline this snow was fairly evenly distributed between north, south and east, with little signs of recent loading.  A sparsely treed ridgeline in the distance  looked much more wind effected with snow being deposited on a SE-S aspect. Noticed a few isolated areas with some wind texture on the surface, but didn’t find signs of slabbiness in the new snow where we traveled. Column tests and hand pits generally crumbed away during isolation, and cracking was confined to a few inches on slopes up to 40 degrees.  Below treeline the old snow interface was generally very weak on north and east aspects. Valley winds were adding some texture to the snow surface in the late afternoon, increasing cohesion.  Found about 10″ of storm snow at 9,660 near splains Gulch at 4pm.

Irwin Cat Terrain

CB Avalanche Center2015-16 Observations

Location: Kebler Pass Area
Date of Observation: 12/15/2015
Name: Irwin Guides
Subject: Irwin Cat Terrain
Aspect: West
Elevation: 10,500-11,500
Weather: Storm was intense this morning with moderate to high winds but quickly calmed down for most of the day. Light snow, and light to moderate winds (westerly) most of the day. Snow and wind picked up around 15:00, and snow intensity increased.
Snowpack: Good Storm with about a foot of fresh. Signs of shallow windslabs in the UWW, but overall stable with no avalanches to report, though a few mini pockets.

Near Treeline: About 30cm’s of new snow with wind drifts & whales very evident. Ski cuts, hand shots, and 9lb airblasts produced widespread shallow cracking (5-15cm’s deep). The storm was a little upside down, probably the same density, though winds probably picked up early morning causing just the top bit to feel slabby. Cracking from shots propagated wide over 100 feet in places, which was surprising because it was only in the top 5-15 cm’s. Some shots and ski cuts produced shallow narrow crowns 10-30’ wide but never really ran. A few ran 50-100 feet.

Below Treeline: No signs of instability or windslabs, ski pen mostly to the ground on JA Steep. I thought we would see some sluffing but no signs of instability. Only a little traffic today in JA Steep Right side not left, but good traffic the past 4-days down in there, all weak snow, no slabs.

Anthracite Mesa

CB Avalanche Center2015-16 Observations

Location: Crested Butte Area
Date of Observation: 12/15/2015
Name: Zoe S. & Heather B.
Subject: Anthracite Mesa
Aspect: North, North East, East
Elevation: 10,500

Avalanches: No avalanches observed in the area toured, but observed some small point release avalanches across the valley on Whetstone.
Weather: Broken/ Scattered Clouds , No precipitation, Calm winds no evidence of blowing snow.
Snowpack: HS 50cm
Measured 15 cm of 0.5-1mm precipitation particles on top of 35cm of 1-3mm facets. Fist hard density throughout the snowpack. No evidence of wind slabs found in the area toured (glades south of coneys on anthracite mesa).
Ski Pen 40cm, Boot Pen 50cm. Snow was completely unsupportive off of the skin track.
Snow temperatures: Snow Surface -10C. 20cm down -3.5C. 40cm down -2C.

Snodgrass Weather Station

CB Avalanche Center2015-16 Observations

Location: Crested Butte Area
Date of Observation: 12/15/2015
Name: Ellie Southworth
Subject: Snodgrass Weather Station
Aspect: North
Elevation: 11,000 feet

Avalanches: None
Weather: Light snow in the AM, slight clearing in the afternoon . Light to moderate winds from the NNE.
Snowpack: About 3 inches of new snow sitting on top of 4F 2mm facets. Snowpack 67 cm on north aspect near the weather station.

Gothic

CB Avalanche Center2015-16 Observations

Location: Crested Butte Area
Date of Observation: 12/15/2015
Name: billy bar
Subject: Gothic
Aspect:
Elevation:

Snowpack: (7am observation) Gothic was missed again with just 1½” new snow and 0.10″ water. Steady wind, 5-12 with gusts to 24, gusting mostly in the past 4 hours. Most of the snow was before midnight. There is 15½” of snowpack. Little to report.

Irwin Cat Terrain Observations

CB Avalanche Center2015-16 Observations

Location: Kebler Pass Area
Date of Observation: 12/14/2015
Name: Irwin Guides
Subject: Irwin Cat Terrain Observations
Aspect: East, West

Weather: Overcast with Light snow, winds were Moderate SSW. Storm slow to start, at 3 pm it got going with S2. 1″ new.
Snowpack: East: Variable snowpack with lots of facets. Anywhere from 4 to 50 cms. Lots of rocks, grass and wind textured surface.

West: Variable snowpack with average HS 30-45cm’s, mostly weak faceted snowpack. Hard wind slab felt (10cm’s) but not reactive with ski cuts or shots.