Location: Crested Butte Area
Date of Observation: 03/20/2020
Subject: Gothic Obs
Aspect: North East, East
Elevation: 9500-10500

Avalanches:Skier triggered a R1D1 storm on a 37 degree rollover. Propagated about 150ft wide, but only ran 50ft downhill

Weather: On and off snow all morning. Sometimes heavy

Snowpack: 14” from the storm when we left up to 17” when we got back

Photos:

Location: Kebler Pass Area
Date of Observation: 03/19/2020
Name: Ben Pritchett
Subject: Red Lady Ob

Avalanches: On slopes steeper than about 35 degrees it was easy to trigger Storm Slab avalanches underfoot and remotely down-slope and on adjacent features 200-300 feet away. Slabs were slow and pushy, generally between 1-2 feet deep, but gather a pretty good head of steam given the dense new snow. Given the terrain we were testing, most avalanche remained on the large side of D1, but where small slides ran into steeper connected terrain below, the slides easily grew to D2’s. Where the old snow surface was crusted, triggering was easy, failing on small facets above the crust. These facets were difficult to isolate on a card and identify given the sticky snow, but no question the sunny slopes had facets failing below the storm snow. On shadier slopes, the storm snow was stubborn to trigger. It was difficult to trigger slabs on steep northeasterly-facing slopes with soft old-snow surfaces, but once avalanches initiated on crusted slopes impacted the shady slopes, they would break too.

Weather: Ridgeline Wind Speed: 20-30 mph
Ridgeline Wind Direction: W
Wind Loading: Moderate
Temperature: 25 F
Sky Cover: Obscured
Depth of New Snow: 28 cm
Depth of Total Snow: 140 cm
Most Significant Precip Rate: S5 – 5 cm/hr
Weather Description: Very snowy day. Started around 3am, didn’t let up until around 6pm. Picked up over a foot of snow, with over an inch of water near Crested Butte. Snowfall reports from riders coming back from around Kebler Pass reported over 20″ new snow. Winds picked up after sunrise, and stayed strong through mid-day.

Snowpack: Snowpack Description: Thick, dense new snow fell on faceted crusts on E-S-W facing terrain. This may be a new Persistent Slab problem.

Photos:

Location: Kebler Pass Area
Date of Observation: 03/19/2020
Name: Eric Murrow
Subject: Anthracites obs
Aspect: North, North East, East, South East, South
Elevation: 9,200′ – 11,500′

Avalanches:
Observed several natural Storm Slabs prior to noon along the Kebler Pass corridor prior to TH, small, steep northerly-facing slopes. around 6 inches deep, below treeline.

Skier triggered around 5 Storm Slabs in the afternoon 12-18″ deep on north and northeast facing slopes in the Anthracites, D1’s, near treeline.
Intentionally skier triggered two Dry Loose avalanches on steep south/southeast facing slopes. D1 in size but fast-moving on the old crust. No propagation observed while running.

Observed a natural avalanche that ran through the “friendly finish” area of the Anthracites. This failed sometime in the afternoon. Could not see crown due to visibility but presumably failed in the drifted start zone above. Although debris was shallow, it was able to run to the valley floor, east facing.

Weather: Obscured skies between 1130am and 430pm out Kebler Pass corridor. Westerly winds transported some snow near ridge top, but less than I would have predicted. Wind speeds at this location generally remained below 20mph at ridgetop. Snowfall was continuous all day with rates between S1 and S3.

Snowpack: New snow accumulations at 11,300′ around 4pm were about 20″ with 1.4″SWE. The new snow was settling to some degree while it was accumulating during the day. New snow was relatively low-density with exceptional ski quality. There was an interface around 2 or 3 inches up in the new snow that was easily identifiable in hasty hand pits that I would suspect was responsible for most of the skier-triggered Storm Slabs in the area (only stuck my mitts into two crowns).

Terrain features that were being pressed or loaded by the wind started to feel top-heavy at the end of the day. Cracks up to a ski length became more common towards later in the day as the snow continued to settle.

Photos:

Location: Crested Butte Area
Date of Observation: 03/19/2020
Name: Evan Ross
Subject: Climax Storm Slabs
Aspect: North East, East
Elevation: 9,000-11,300

Weather: Calm wind with a couple strong gusts during our short stay at 11,000ft. We headed out after the peak precipitation in the morning, so S1 throughout our tour.

Snowpack: Let’s start small to large. We struggled to get out of easterly tilted slopes in this generally NE facing terrain. Where there was a crust at the old snow surface, the storm slab avalanche problem was reactive on 40+ degree terrain. 30-degree terrain would produce some cracking but wasn’t steep enough to get things moving unless the slope was unsupported. These slabs broke below skis and didn’t propagate very wide. They never pulled down from above. Initiation was at or just above the crust. More northerly facing slopes that didn’t have the crust at the old snow surface were more stubborn to trigger and didn’t run as well on the softer bed surface. HST and crown height was in the 25 to 30cm range. These avalanches were all D1 in size until reaching near treeline start zones. A couple of natural D1’s were also observed.

Getting up to the 11,000ft elevation and into steep NTL start zones, terrain avoidance was obvious given the instabilities found at lower elevations. A simple ski cut produced a wider propagating Storm Slab with a crown in the range of 30 to 40cm range. This crown didn’t propagate horizontally through the terrain, but in a steep downslope frown that was difficult to see how far across the slope it went. Debris from that avalanche were later observed 2,000ft below. This is perfect terrain for producing long-running avalanches.

We worked our way down on ribs in the terrain where you could shred pow above where the small Storm Slabs would initiate. Given the consisted and steep slope angels of this terrain features, the small slabs accumulated mass and kept running to near valley bottom. This terrain is also one of those places to find some of the worst-case avalanche problems in the CBAC FX Area. We found just that when a small Storm Slab stepped down and triggered a larger Persistent Slab failing at the ground in a shallow weak snowpack. That avalanche stepped down on the 3 rollers in the terrain it passed through. Each added mass and produced a D2.5 avalanche by the time it got close to the valley bottom. I don’t think we could have human triggered one of these deeper Persistent Slab Avalanches, and the bigger mass of an avalanche was needed to start gouging things out.

Location: Crested Butte Area
Date of Observation: 03/19/2020
Name: BA
Subject: Sluffs and Small Storm Slabs
Aspect: North, North East, East, South, South West, West
Elevation: 9,400′-11,000′

Avalanches: 3rd bowl Snodgrass – Multiple D1 storm slabs and small, slow moving dry loose triggered on NE, mostly small terrain features steeper than 35 degrees. Storm slabs were 4F/4F- and breaking on the new interface or within the storm snow. Dry loose were all within storm snow. We avoided any large terrain features that would have held potential for larger storm slabs.

Weather: Snowing all day with lots of variation in snow types and density throughout the day. Winds increased around 2pm, but not enough to transport significant amounts of snow in our sheltered areas.

Snowpack: Variable amounts of new snow and significant accumulations throughout the day, up to 30cm in places by afternoon. No signs of instability anywhere besides 3rd bowl. Skiing was excellent.

Location: Crested Butte Area
Date of Observation: 03/19/2020
Subject: Snodgrass Storm Slab
Aspect: North East
Elevation: 10,500

Avalanches: Skier triggered a couple storm slabs on 3rd bowl crown was 6 to 8” deep

Weather: Moderate snow and low visibility most of the day

Snowpack: New snow wasn’t bonding very well with the crust below