Speedy dry sloughs near treeline

Location: Kebler Pass Area
Date of Observation: 04/03/2019
Name: Eric Murrow

Subject: Speedy dry sloughs near treeline
Aspect: North, North East
Elevation: 9200′-12000′

Avalanches:

Observed several natural, tree bomb triggered, dry loose. Skier triggered numerous dry loose in steep, NTL terrain.

Weather: Cloudy skies with periods of snow, heavy at times. New snow accumulations at 12,000 feet, 1pm was 4 inches. Winds were lighter than expected, under 15mph while in open terrain at 12k. Visibility was limited but hung out for 30 minutes in open ATL terrain and observed almost no transport.

Snowpack: Visibility was too poor to venture into terrain with possible Wind Slab development. Skiing in steep NTL protected terrain produced fast moving shallow sloughs. Sloughs were able to entrain just a small amount of old snow at NTL elevation. Snow surface remained dry on northerly slopes down to about 10,400′ before becoming moist.

Photos:

Greenhousin’ and wet snow

Location: Kebler Pass Area
Date of Observation: 04/02/2019
Name: Eric Murrow & Zach Kinler

Subject: Greenhousin’ and wet snow
Aspect: North, North East, East, South East, South
Elevation: 9200′ – 11500′

Avalanches:

A couple natural D1 wet loose avalanches on southerly slopes near treeline. Easily triggered D1 wet loose slides on southerlies in the top couple inches of snow running on a crust – entrained little mass. Northerly slopes near treeline also produced skier triggered shallow loose avalanches in steep terrain – the snow was just slightly moist.

Weather: Partly cloudy skies in the morning with a mix of thin high clouds. Temperatures warmed near the freezing mark up to 11500′. Winds were out of the west blowing light with occasional moderate gusts. Skies increased to mostly cloudy around 2pm with a few flurries.  Snow surfaces warmed more than expected from good solar input in the AM along with the mild temperatures.

Snowpack: Less than an inch of new snow overnight, no accumulations during the day. Snow surfaces became moist at valley bottom and southerlies by 1030am and by 130pm, it was easy to trigger shallow, slow-moving wet loose avalanches on southerly slopes at 11,500 feet. North facing slopes became slightly moist up to around 11,500′. Shaded slopes had around 10 inches of snow resting on the 3/29 interface near treeline.

Photos:

Mt Emmons

Location: Crested Butte Area
Date of Observation: 04/01/2019
Name: Eric Murrow and Zach Kinler

Subject: Mt Emmons
Aspect: South East, South, South West
Elevation: 9,000-12,343

Avalanches:

Only a couple very small skier triggered loose dry in steep and extreme terrain.

*Received at a report of a skier triggered wind slab on a south aspect at 12,500′, 8 to 10 inches deep* – this came in the evening via test message, not from Mt. Emmons

Weather: Morning fog and low clouds burned off by mid morning with partly cloudy skies and strong solar following. WNW winds were moderate at times with stronger gusts at ridge top. Temperatures remained in the lower to mid 20s.

Snowpack: Trace to 2″ new snow on supportive MFcr that was 5 to 8cm thick on SE-S aspects above treeline. Winds were moving small amounts of snow onto leeward slopes in the alpine.  Drifting up to 10″ deep was found on SE slopes above treeline immediately below ridge tops and cornices.  Very minor cracking in drifts.  Snow surfaces remained cold on southerlies near and above treeline where temps remained below freezing and cold winds prevented warming. On a quick check of a Cornice triggered slab avalanche in Red Lady Bowl, we found the avalanche failed in a layer ~60 cm from the surface and stepped down another 60 cm or so. Perculation columns were found in the area of the first failure layer.  It is unknown if those were recent and contributed to this avalanche or if they occurred during the warming last week and the avalanche was solely a product of the weight of the cornice overloading dry weak layers.  This slope also had avalanched catastrophically during the early March storm cycle.

Photos:

RMBL Study Plot

Location: Crested Butte Area
Date of Observation: 04/01/2019
Name: RMBL

Subject: RMBL Study Plot
Aspect:
Elevation: 9500

Avalanches:

Weather:

Snowpack:
Photos:

Red Lady Cornice Slide

Location: Crested Butte Area
Date of Observation: 03/31/2019
Name: Brooke Warren

Subject: Red Lady Cornice Slide
Aspect: South East
Elevation: 12,400

Avalanches:

A Sprinter van-sized cornice was accidentally triggered when a snowboard was placed in the snowpack during transition at the flags at the top of Red Lady bowl. The cornice triggered an avalanche directly below the drop that propogated about 10-15 meters wide. The avalanche was about 80 cm deep, to the ground, exposing rock and grass. The debris slid to the rollers at the bottom of the bowl. One person’s pack and poles were lost in the debris, but the pack was found on top of the debris at the base of the slide.

Weather: Overcast, slight wind and light snowfall.

Snowpack: Snow conditions ranged from crusty to icy with a thin layer of fluff.

Photos:

Fresh Very Large Avalanche Paradise Divide

Location: Paradise Divide Area
Date of Observation: 03/30/2019
Name: Evan Ross

Subject: Fresh Very Large Avalanche Paradise Divide
Aspect: North East, South East, South West
Elevation: 9,500-12,940

Avalanches:

Skier triggered a very small surface slab just off a high summit and some sluffing. All easy to manage and small in size.

The outlier: I came across a freshly triggered very large avalanche on the way home. S to SW aspect at about 11,800ft. A snowmobile track entered and exited this very large avalanche. The track appeared to go through a thin spot in the slab near some bushes and raised ground. The track further appeared to have splatted on the crown face but had enough momentum to keep going up. I checked out two parts of the crown that were near where the snowmobile track exited. The first was to the lookers right. HS was thin and about 80cm. Basal depth hoar was massive and estimated at 5mm. An ice lens capped these facets and they were also moist. The next quick crown profile was closer at about 20 ft to the looker right of where the track exited. Here HS was 180cm. The crown was 90cm. The basal facets where smaller, also moist and again an ice lens capped these facets. The avalanche appeared to have failed at this ice lens or at the interface with the basal facets. Shortly after getting to that location water started running like a faucet out of the new/old snow interface and I quickly packed up and left. Slope angles were estimated to be near 40 degrees where the snowmobile track left the crown. Crown hight averaged an estimated 70cm. The crown appeared to propagate into a deeper snowpack area.

Weather: Partly Cloudy over the greater forecast area, but my face will tell you that I was in an area that was in the sun all day. Convective clouds where moving very slow, keeping some areas in the clouds and other hanging in the sun all day. Calm winds. Strong Solar.

Snowpack: The March sun was doing its thing and warming snow surfaces. Storm totals were only about 1″ down in the valleys and about 5 to 6″ at upper elevations. The new snow posed little avalanche issues. Sluffing in steep terrain and some deeper drifts to stay mindful of.

Red Lady Glades

Location: Crested Butte Area
Date of Observation: 03/29/2019
Name: ADB

Subject: Red Lady Glades
Aspect: South
Elevation: BTL
Snowpack: Snow Survey at Keystone:

Depth 62 inches or 5 feet
SWE: 22 inches
Density: 30%

Ice lens near the ground.

West Brush Below Treeline Observations (Grand Traverse Course)

Location: Brush Creek Area
Date of Observation: 03/27/2019
Name: Ian Havlick

Subject: West Brush Below Treeline Observations (Grand Traverse Course)
Aspect: East, South East, South, South West
Elevation: 8500-9500

Avalanches:

no avalanches triggered, however thought with the collapses I observed/triggered so close to steep terrain that remote triggering could be possible. Did observe D2 Gibson Ridge wet slab failing between 1300-1530 yesterday. Steep, easterly BTL terrain that previously slid this year. Also numerous fresh glide avalanches low angle, east facing in Brush Creek, on Mt. CB massif.

Weather: Extremely warm, t-shirt weather, no gloves even on snowmobile. Light SW breeze but barely noticeable. Intense solar despite high clouds. Thicker cirrus around 1500.

Snowpack: Only traveled southerly BTL in Brush Creek yesterday. Boot pen was 20cm off skis, but if “dropped weight” foot would plunge to ground.- illustrating pronounced slab structure remains intact. Traveled intentionally late in the afternoon to observe characteristics of wet, warm snowpack. Snowpack is wet, large grains in upper 30cm, and below that, remains colder, moist, finer grained more midwinter snowpack. Numerous rolling collapses, dropping 3-5cm in places and propagating over 200ft on 20º terrain.

Photos:

Large Avalanche Debris on Cement Creek Rd

Location: Cement Creek Area
Date of Observation: 03/27/201

Subject: Avalanche Debris on Cement Creek Rd
Aspect: East, South East
Elevation: ~9,300ft

Avalanches:

Wet Avalanche Debris on Cement Creek Rd in the lower pinch, above the campground. From the observer: “Looked like it started in the cliffs. Didn’t see an obvious crown.

Other Than Surface Issues, The Deep Snowpack Was Holding Up Ok.

Location: Paradise Divide Area
Date of Observation: 03/27/2019
Name: Evan Ross

Subject: Other Than Surface Issues, The Deep Snowpack is Holding Up Well.
Aspect:
Elevation: 9,500-12,500

Weather: The high temperatures can speak for themselves. The high clouds thicker in the afternoon helping to cap the warming, but they may have helped green house some slopes. At the highest elevations traveled winds were generally light, with some moderate gusts. Couple rumbles of Thunder in the late afternoon.

Snowpack: More or less the same story on a different day. The snow surface is transitioning, so there appeared to be less natural loose wet avalanche activity today. However wet snow could still be human triggered on steep slopes in the upper 30 degree range. A wet or moist snow surface is making its rounds at all elevations and has stretched into some NE slopes.

Never ran into something that felt like Wet Slab conditions. The layer of snow deposited by the early March Storm is thick, strong and will need time for water to move through it. Probably going to need a shallow snowpack area like a repeater avalanche slope or steep cliffy terrain, or other below average thin snowpack areas, somewhere that water can get through that otherwise thick layer of snow.

Dug in a very snow favored part of our forecast zone. 28 degree, South aspect at about 10,700ft. Protected slope that felt like a solar oven. HS 275. Wet snow was down to 40 cm, with boot pen close to the same at 1pm. Below that wet snow there was a couple of ~3cm layers of large grain moist snow in the next 30 cm’s of the snowpack. The 2/28 interface was non problematic and 110cm’s below the snow surface.

Dug again in Washington Gulch on the flank of Gothic Mountain. SSW aspect, 28 degree slope, 10400ft. HS 305. Wet snow was down ~25cm and again boot pen was similar. There were some thin ice lenses in the upper snowpack, but again the water was far from impacting the deeply buried 2/28 interface.