Date of Observation: 12/23/2020
Name: E-Murrow, Z-Kinler, Da-Bum, E-Ross

Zone: Northwest Mountains
Location: Purple Ridge
Aspect: North, North East, East, South East, South
Elevation: 9,500-11,300

Avalanches: Remotely triggered a large Persistent Slab Avalanche. NE Aspect, 10,450ft. This avalanche failed on, or very near, an up route that is typically used to access the Purple Palace. The crown was estimated to be about 2.5ft thick, propagated a couple hundred feet wide and ran about 800ft to the creek below. SS-ASr-R2-D2-O
Weather: Cold, S-1 snow through the day, overcast and obscured sky. Strong winds picking up in afternoon and transporting snow throughout the tour at all elevations.
Snowpack: The terrain was less ravaged by the previous wind event than expected. Still plenty of wind erosion, and wind-loaded terrain features. Many of the bigger NE facing slopes that we traveled near, had previously avalanched earlier this winter and had about 20cm’s of snow on those old bed surfaces. Other NE facing slopes had wind erosion in their uppermost start zones where we could get close, and not holding the same snowpack that would be expected further down the slope.

Surface hoar was found below treeline in sheltered locations, just beneath the few inches of storm snow, that faced northeast and north, but was quite small, around 3mm.  Not particularly concerning moving into the future for terrain traveled. Did not find it on wind-exposed east slopes below treeline.

Obvious signs of instability have decreased as the upper slab consolidates and grows in size. Still plenty of large collapses and shooting cracks while traveling E to NE facing slopes with slope angles below about 34 degrees. Typically you need to jump to get a result now, versus just walking about. 1F slabs were failing on average 30 to 60cm’s deep on the 12/10 interface. In this area those Near Surface Facets were about 1.5mm in size, F hard, but not overall as week as the same weak layer found closer to Crested Butte.

We traveled a few SE and S facing slope. This had just a couple of inches of new snow on a breakable melt/freeze crust. These were not recently wind-loaded slopes and no current concerns were found.

New snow in the area was probably in the 3 to 4″ range.  Highly variable given all the recent winds.

Date of Observation: 12/23/2020
Name: billy barr

Zone: Southeast Mountains

Weather: Snow started late afternoon though was never more than very light.  Mostly blowing snow that let up by midnight with 1½” new and water 0.13″.  Wind gusts passed 40 mph at the station site and most certainly stronger up valley, though now a more reasonable 5-10 NW.  Currently cloudy with the temp. 4ºF (the morning low) after a high of 34F yesterday.  Snowpack is currently at 22″.  But today is 5 seconds longer than yesterday! (oh my, what to do with all that extra daylight!).

Date of Observation: 12/21/2020
Name: Eric Murrow

Zone: Northwest Mountains
Location: Sunnier side of Baldy
Aspect: East, South East, South, South West, West
Elevation: 9,500′ – 11,800′

Avalanches: While heading out Slate River Road noticed two unreported avalanches on the far end of Schuylkill Ridge and the sub-peak of Schuylkill Mountain. Both avalanches were easterly near-treeline features. I suspect they ran on Saturday or Sunday. Both D1.5’s
Weather: Sunny day, with mild to warm temperatures with light winds near and below treeline.
Snowpack: Recreational ski day just enjoying the sun. Southerly slopes near and below treeline had a soft melt-freeze crust at the surface in the morning that became moist throughout the day (exited terrain by 1pm). I suspect supportive melt/freeze crusts will develop from today and tomorrow’s forecasted mild weather on steep, sunny slopes near and below treeline. Lots of collapsing on low-angled south-facing slopes that are of little concern. More concerning was walking around the top of small east-facing, near treeline features, I was able to produce a collapse that shook a small wind-lip well over 100 feet away – slope was only 25 – 30 degrees steep so it did not slide (it took a bit of wandering around until I was able to produce the collapse, classic PSa behavior). Briefly moved over several west-facing near treeline features and produced a collapse on each but slopes angles were only about 30 degrees so nothing moved.
Skied several short steep south and southwest facing features without result, quick pole probing did not reveal any concerning structure.

Photos:

Zone: Northwest Mountains
Location: Ruby Range
Date of Observation: 12/20/2020
Name: Zach Kinler

Aspect: East

Elevation: Above Tree Line

Avalanches:

This picture from Baxter Basin was passed on to the CBAC sfaff.

2 large persistent slab avalanches on East aspects of Richmond Mt. Both of these initiated from ridgeline and quickly stepped down to weak layers in the lower snowpack. Debris from both avalanches triggered additional slab avalanches lower in the track.

Zone: Northwest Mountains

Date of Observation: 12/20/2020

Subject: Wind slabs

Aspect: South East, South

Elevation: N/ATL

Avalanches:

Spotted a few more recent persistent slab avalanches fitting the usual pattern.

Weather: Moderate ridgetop winds. High clouds thinned through the day.

Snowpack: Rec skiing on southerly aspects to take a break from looking at persistent slabs. We had to manage for small windslabs that were easy to identify and avoid. Wind drifted slabs were 8” to 10” thick near treeline, easy to produce cracking on moderate slope angles. Above treeline, wind slabs were up to 18” thick and harder (1F) and more stubborn. These were all cracking on lower density snow from earlier in the week. We also got several rumbling collapses on lower angle terrain where buried sun crusts (2 feet deep) are thinner than on steep aspects. The basal structure transitions from a strong crust on steep south to a thinner, weaker, more collapsible crust on ESE.   We avoided drifts and stayed on more southerly pitches with no avalanche activity.

Photos:

Zone: Northwest Mountains

Location: Kebler Pass Road and Anthracites

Date of Observation: 12/19/2020

Subject: Kebler

Aspect: North East

Elevation: BTL

Avalanches: A few more freshies to add to the list: Gibson Ridge (D1.5) and Kebler Pass Road (D1), both below treeline.

Weather: Moderate northwest winds through the day with drifting snow ongoing. Sunny skies gave way to mostly cloudy skies and light snowfall.

Snowpack: Limited travel off of skin track and debris today, be we got several localized collapses on open slopes. Test pits on shady aspects BTL produced easy to moderate propagating results on the 12/10 facet layer, buried by a two foot soft slab. On heavily windloaded terrain, that layer was up to 5 or 6 feet deep. Also got some shallow cracking in wind drifted features.

Zone: Northwest Mountains

Location: Irwin Tenure

Date of Observation: 12/19/2020

Subject: More action

Aspect: West

Elevation: N/BTL

Avalanches:

Worked primarily in the West today near and BTL. Paths still running full track with a whiff of a trigger. Ski pressure is more effective than explosives. Many rocks and logs. Full junk show

Weather: Wind up high. Solar aspects grew moist.

Photos: