Date of Observation: 03/12/2021
Author: Jared Berman, Zach Guy
Zone: Crested Butte Backcountry
This week we saw many different avalanche types from wet slabs to dry slabs. Learn all about why this happened and what this means down the road in this week’s Weekly Summary.
Date of Observation: 03/11/2021
Name: Jack Caprio, Evan Ross, Zach Kinler
Zone: Northwest Mountains
Location: Skooks
Aspect: North, North East, East
Elevation: 9,000-11,400
Avalanches: No new avalanches observed.
Near ridge line, we initiated collapses along with radiating cracks on recently loaded NE to E facing start zones.
Weather: Broken skies for most of the day. Periods of S-1 snowfall. Light winds.
Snowpack: We went hunting for information on our recently buried March weak layer ahead of this weekends storm. Below tree line, the weak layer is buried by 4” of recent snow. On easterly facing slopes around 9.5k, the interface consisted of a soft 2” thick MF crust resting on top of 1-2 mm facets. Quick shovel shear tests at this site produced easy failure results just below the crust. As the compass tilted north-east the crust became softer and weaker. On due north slopes the interface consisted of 1-2 mm near-surface facets. As we gained elevation we continued trying shovel shear tests that produced failure both above and below the crust. We saw some cracking and got a couple collapses on leeward slopes just below ridgeline where 12″ or more of new snow had drifted over the weak new/old interface.
We also tested the 12/10 interface at a deeper, near tree line site. At this site, the 12/10 interface was buried 110 cms below the surface and consisted of 4F 2-4 mm DH. A pencil hard 110 cm slab is resting on top of this interface at this location. A PST test resulted in unlikely propagating results (80/110 END down 110 cm). The 12/10 depth hoar was moist and seemed to be showing signs of rounding and sintering.
Date of Observation: 03/10/2021
Name: Alex Tiberio
Zone: Southeast Mountains
Location: Gothic
Elevation: 9500
Photos:
Date of Observation: 03/10/2021
Name: billy barr
Zone: Southeast Mountains
Weather: Obscured and with off and on snow starting towards midnight. Strong wind has made for drifting snow and blizzard conditions. There was 4″ new snow and water 0.39″ with 44″ on the ground. Wind has been generally moderate with strong gusts up to around 40 mph. Currently obscured with light snow but wind continues, though gusts down to 25 now. Yesterday high was 44F and the current is 16F which is the morning low. It is generally blizzard conditions.
Date of Observation: 03/07/2021
Name: Ian Havlick
Zone: Southeast Mountains
Location: Red Coon Glades
Aspect: East, South East, South, South West
Elevation: 9000-11,200
Avalanches: Only fresh avalanche observed today was the D1.5 wet loose in Red Lady Bowl.
Weather: Solid inversion this morning with valley temps in teens and 12,000 not dipping below 25F. Very light westerly winds, rapidly warming temperatures between 8:30 and 10:30am. Overcast skies for most of the day aided the greenhouse effect and snow surface warming.
Snowpack: Snowpack started with a decent freeze below 10,500ft, but quickly softened on southerly facing BTL and NTL terrain by 10am, especially above the inversion (~10,500ft). Persistent slab structure in all south facing elevations today, but not until the more open “Red Coon Glades” that we found alarming, punchy, wet snow. After pole probing tipped us off to the poor, unconsolidated structure, I jumped to demonstrate to the level 1 students how punchy the snow had become and initiated a large “whumph” across the whole 24º steep meadow. We pulled the plug on the rest of our ascent after I dug a subsequent test pit and got an ECTP14 SC on moist large grained depth hoar 80-100cm deep (near ground, Dec 10th DH). On a small south facing test slope near the parking lot, initiated a 10’x10′ wet slab to fail and slide 4-6″ in a relatively shallow snowpack area, ~38º in steepness.
Factors that lead to turning around:
1. recent wet slab avalanche in nearby Coon Basin, similar aspect and elevation
2. Signs of instability, whumph
3. Propagating extended column test with moderate loading step on moist depth hoar near ground
4. Poor re-freeze above valley inversion
5. rapid temperature rise, and 3-4th day of above average temperatures.
Date of Observation: 03/07/2021
Name: Justin Blair
Zone: Southeast Mountains
Location: Red Lady Bowl
Aspect: South East, South
Elevation: 12,000
Avalanches: As advertised, some wet slides this afternoon in Red Lady Bowl. Unsure of how triggered.
Photos:
Date of Observation: 03/06/2021
Name: Ben Pritchett
Zone: Northwest Mountains
Location: Heli flight along the Elk Mountains Grand Traverse route
Aspect:
Elevation:
Avalanches: Remarkably few recent avalanches. Only observed one fresh Wet Slab avalanche, and no previously unreported Wet Loose avalanches. We saw numerous large Persistent Slab avalanches seen from the mid-February avalanche cycle, but these were primarily restricted to near treeline, in areas of generally weaker, shallower snow cover. High alpine terrain showed few signs of large to very large avalanches. Those Persistent Slab avalanches seen tended to be wind-loaded features lower on the mountain in areas with weaker snow cover. The big alpine paths in the Star Pass area have not yet gone through a major avalanche cycle this season.
Weather: Hot and calm
Snowpack:
Photos:
Date of Observation: 03/06/2021
Name: geo bullock
Zone: Southeast Mountains
Location: North side of coon Basin
Aspect: South East
Elevation: 11,500
Avalanches: I triggered an avalanch 8-18″ deep and 70′ wide, ran 500′ vertical to the bottom of coon basin.I traversed under the cornice intending to take an easier route and quickly went from dense snow to shallow wet snow and rocks (see picture).went for a ride maby 200′.managed to stand up on my skis (see dirt spot) and let it pass. the intention was to ski down the ridge not coon basin. I was too late in the day to be on that pitch. the slope angle at the trigger point was at least 40
Weather: high overcast light breeze 40 degrees
Snowpack: 65cm wet snow
Photos:
Date of Observation: 03/06/2021
Name: Andrew Breibart
Zone: Northwest Mountains
Location: GMT Reduction (East River-Paradise Divide-Washington Gulch)
Aspect:
Elevation: BTL, NTL
Avalanches: didn’t take pictures of the wet loose avalanches on south aspects of Baldy and east aspects of Gothic.
1. Mt Belleview-NTL on W/SW aspect: slab avalanche (D1 to D2) CBAC NOTE – reported 2/22 ob here
2. Mt. Baldy-NTL on SW aspect wet slab
3. Coneys-BTL on E/NE aspect: slab (D0.5-D1) CBAC NOTE – reported 3/2 ob here
Weather: Temperatures remained lower than yesterday’s sauna due to thin cloud cloud cover. Calm.
Snowpack: snow is transitioning rapidly on southern aspects BTL as a melt freeze crust develops.
Photos:
Date of Observation: 03/05/2021
Name: Ben Pritchett and Bo Torey
Zone: Southeast Mountains
Location: Upper Cement Creek and Upper Taylor River
Aspect:
Elevation: up to 9,000-12,400′
Avalanches: 3 small wet loose avalanches ran above treeline on steep rocky south-facing slopes in the Upper Taylor River headwaters. Surprisingly no other wet loose avalanches observed. Numerous roller balls seen, but none that gouged or spread into a pushy wet avalanche.
Weather: Ridgeline Wind Speed: Calm
Temperature: 43 F
Sky Cover: Clear
Depth of Total Snow: 150 cm
Weather Description: Warm, calm day. No blowing snow observed.
Snowpack: The upper snowpack is gaining strength and making it more difficult to influence weak snow below. Average snowpack in the upper Cement Creek and upper Taylor River headwaters area ranged from 130-160cm. Multiple ECT’s failed to produce propagating results in the normal loading steps. Removing part of the slab, and slamming on the remaining thin slab did produce a propagating result in one profile. East to south to west-facing slopes with a lot of sun have grown crusty, with rills developing in the snow surface near and below treeline. We experienced a pair of collapses, with long-running shooting cracks, over 50′ long, in the valley bottom. Alpine surfaces are highly variable, with a few inches of fresh snow obscuring highly textured and dense old wind textures. Near treeline shady surfaces were soft, but dense enough for reliable sled and boot support.
Photos:
