Observations

Zone: Northwest Mountains

Location: Anthracites

Date of Observation: 12/11/2020

Name: Eric Murrow

 

Subject: Kebler Pass ski

Aspect: North, North East, East

Elevation: 10,000 – 11,500

Avalanches:

Intentionally triggered one dry loose avalanche that quickly gouged into old snow. Slope was small, but debris volume was bigger than you would expect with only 5 inches of new snow.

 

Weather: Overcast skies, consistent light snowfall with several short periods of moderate snowfall (S-1 to S2), and generally light winds with occasional moderate gusts from westerly directions.

Snowpack: New snow at Kebler Pass/Antracites was 4″ at 10am and reached 6″ by 3pm. Relatively low-density snowfall. Intentionally sought out terrain features without previous traffic and found loose avalanches were easy to trigger in the new snow that quickly gouged around 6 to 8 inches into old surface (see photo). While hunting for drifted areas was able to produce some cracking to the old snow interface, but propagation was no more than 10 feet and cracks only 6 inches deep. By 230 pm snow surfaces in open north-facing terrain showed more signs of cracking but only shot a ski length in front of you.

Photos:

 

Zone: Northwest Mountains

Location: The Deep Slate

Date of Observation: 12/11/2020

Name: J B

Subject: 20201211 Storm Obs

Aspect: North East, East

Elevation: 9400-11400

Avalanches:

Innumerable remote, natural, and ski cut triggered D1 avalanches within the storm slab. Crowns broke down to the old snow, but primarily slumped and stayed in place with the exception of the top 5-10 cms of new snow which did not run far. Avalanches were concentrated to convex rolls over 38 degrees. The largest slide was triggered by a ski cut near rocks on an old bed surface and piled up enough snow on the uphill side of trees to bury someone to their waist but would not have ended their days- larger D1 with a crown of 70m wide and 40cms deep (SS-AS-R2-D1+-I).

 

Weather: Steady snowfall 2-3cms/hour from 10am to 2pm. Clearing up around 2pm. Light winds. No observable wind transport of new snow or solar effect. Felt cold, 20 F?

Snowpack: 45 cms of new snow by 2pm!! That’s a foot and a half for you imperial goons. The new snow doubled the existing snow depth in spots. Old snow interfaces were a mixture of sun crust on E-S aspects and faceted dry shallow on anything with a hint of North to it.

Photos:

 

Zone: Northwest Mountains
Location: Skylkill Ridge
Date of Observation: 12/11/2020
Name: Evan Ross

Aspect: North East
Elevation: 9,200 to 11,200

Avalanches: Natural avalanche activity spiked mid-day during a period of heavy snowfall. Soft slabs of new snow failing on the very weak, faceted, old snow. Many D1’s near treeline and a few D1’s below treeline. About five D2’s and, one D2.5 near treeline. For the most part, these were very soft slabs that just slumped into the weak facets below, started moving, then stopped 50 to 100ft downhill. Others initiated the same way, but continued to gain momentum and entrain the full snowpack.

Not all these slabs propagated widely, but there were some standouts. Runaway Ski propagated across most of its start zone and continued all the way across Thanksgiving. Runaway Ski mostly just slumped and was D1 in size. While Thanksgiving ran nearly wall to wall and hit the bench. Even the skiers left shoulder in Runaway pulled 90% of that terrain feature.

Yogy’s had a soft slab propagate across 80% of its start zone. The skier’s right side mostly slummed and continued to run about 1/2 way to the bench as a D1.5. While the skier’s left side quickly entrained the full snowpack, and was estimated to be D2 in size, I couldn’t see how far the skier’s left side ran given poor vis.

The crown lines on these avalanches were already getting hard to see from a distance given their soft slumpy character, and the 15-30cm crowns were filling back in.

Weather: Fairly consistent snowfall from the time I headed out at 9:30am until 2:30pm. Mostly S1 to S2 with a period mid-day near S5. Mostly light winds at ridgeline, drifting snow during brief periods of moderate gusts.

Snowpack: The avalanche danger increased quickly sometime around 11am to 1pm. During the morning, test slopes were collapsing and shooting cracks up to about 15ft. As the day progressed that activity increased and many small avalanches were remotely triggered up to a couple hundred feet away. For the remote triggers that were further away I think it was an interesting chain of events with one small slab beginning to move, then sympathetically triggering another further away, and another… All the avalanche activity was silent and I never felt a collapse.

The entire snowpack was mostly unsupportive to skis making for scary downhill travel with all the hidden ground hazards. HS generally averaged 40 to 50cm’s down low and 80 to 90cm’s closer to 11,000ft.

HN was about 30cm at 11,000ft and 25cm’s in the valley bottom at 9,200ft.

 

Zone: Crested Butte Backcountry
Date: 12/11/20
Name: Jack Caprio/ Zach Guy

After a very long stint of high pressure, we finally have a storm system making its way into the Crested Butte area. Take a look at the weekly weather/ snowpack summary to see how our snowpack stacks up before this new loading event.

Zone: Northwest Mountains
Location: Purple Ridge
Date of Observation: 12/09/2020
Name: Zach Kinler and Eric Murrow

Subject: Sun and Serotonin

Aspect: North, North East, East, South East

Elevation: 9800-12,200′

Avalanches:

No new avalanches observed.

Weather: Brilliant. Cold in the valley, spring-like above the inversion with above freezing temps. Light westerly wind at ridge top. Whispy clouds moving in late in the afternoon.

Snowpack: Toured SE-E-N aspects enjoying the comfortable conditions while looking at surface conditions as we approach a loading event this weekend. East aspects were weakest in this area, as we have seen from other zones, with 15-20cm of large grain facets resting on weak crusts below 11k and a more supportive windboard/mid pack slab above 11K. Moving to North aspects above tree line, surface conditions reamin weak with 3cm of near-surface facets resting on a soft windboard which varied from 2cm to 10cm across the slope.

We got additional data from SE aspects which appear to be on the “naughtly list” as well. At 10,200′ a razor thin melt-freeze crust caps 15cm of faceted grains which are resting on a Pencil hard melt-freeze crust. This will provide an efficient weak layer/bed surface combination for future avalanches.

Photos:

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Name: Jack Caprio

Zone: Northwest Mountains

Location: Baxter Basin

Date of Observation: 12/09/2020

Aspect: North, North East, East

Elevation: 9,500-11,500

Avalanches: Old natural and skier triggered dry loose avalanches on East, Northeast, and North Facing aspects above treeline. Some naturals were initiated due to solar warming near rock bands on east-facing terrain.

Weather: Just lovely. Little to no wind and sunny skies.

Snowpack: We toured primarily on North, Northeast, and East facing aspects from 9,500′ to 11,400′. At 10,000 feet, we found about 10-15 cm of 2-4 mm fist hard facets on the top of the snowpack. Below that, we found 30 cm of 1 finger dense snow down to the ground. As we gained elevation, we toured primarily on the northern quadrant of the compass.

At 11,400 feet, on an open north-facing aspect, the snowpack depth was 75 cm. The upper 25 cm of the snowpack was fist hard facets, while the next 40 cm had a 1 finger density.  This particular area held 10 cm of old late October snow at the bottom of the snowpack. This old October snow showed significant signs of rounding. After a couple of non-propagating test results, we skied 35-38 degree NNE facing slopes with no signs of instability.

Photos:

 

Zone: Northwest Mountains
Location: Anthracites – standard skin up and east bowl down
Date of Observation: 12/08/2020
Name: Eric Murrow & Zach Kinler

Subject: Kebler Pass obs

Aspect: North, North East, East

Elevation: 10,000 – 11,250′

Weather: clear skies, mild temperatures, and light wind. Do clouds form here?

Snowpack: Went for a quick tour around the Antracites looking at north and easterly slopes checking on snow surfaces and the loose snow avalanche problem. On a northeast-facing slope at 10,700 we found 70cm deep snowpack (a bit more than 2 feet) with 20cm (8 inches) of fist hard, weak snow at the surface and 1 finger snow below that.  2 inches below surface a Surface Hoar layer was identified and had faceted grains chained to it (see photo). Any loose snow avalanches in this type of snowpack would remain small and generally not much of a problem. On a north-facing slope at 11,200′ weak snow was around 20cm thick at the surface but looking through a magnifying lens the faceting was much more subdued with far fewer sharp angles. Again 1 finger snowpack below that was very supportive to skis. Descended east-facing terrain from 11,200 feet with a snow depth of 60cm (2 feet) and found noticeably weaker snow at the surface. Faceted grains were larger and well-formed with Surface Hoar layer mixed in a few inches below surface sitting on a 1 finger hard snow below. East-facing slopes continued to weaken on the descent down to 10,000 feet. The take-home point from this tour was east slopes seem to have weaker, and more developed facets near the surface than similar north slopes.

Photos:

 

Zone: Northwest Mountains

Location: Kebler Area

Date of Observation: 12/06/2020

Name: Cam Smith

 

Subject: Kebler Area

Aspect: North, North East, East, South

Elevation: 10 – 12k

Avalanches:

Small broken cornice in the entrance to a south facing gully. A few spots where surface facets had rolled down but really nothing to shake a pole at.

Weather: Calm, sunny, but didn’t feel nuclear hot this morning up high.

Snowpack: Skied one narrow NE facing chute that was obviously cross loaded but the surface snow was not cohesive. Top inch or two would stuff off. Just as one might expect with very weak facets on top, total trap door at the bottom, and soft snow between. An adjacent wider N facing chute actually seemed more scoured. The top few hundred feet felt more like a supportable solid wind crust before turning into more the mixed bag we’re all seeing.

Melt freeze crust on a steep high southerly was solid to the ground. All the joys of spring skiing, just with 1-4” of snow.. if you’re into that kind of thing..

Zone: Northwest Mountains
Location: East bowl of Schuylkill Peak above Pittsburg rollers
Date of Observation: 12/6/2020
Name: Zach Kinler, Jack Caprio

Aspect: North, North East, East, South East

Elevation: 9,400′- 11,600′

Avalanches:

Observed 6 older Loose Dry avalanches on steep E-N slopes initiating from shallow areas around rock outcrops near tree line. All D1 in size confined to surface snow.

Triggered 4 Loose Dry avalanches from ridge line in similar terrain, running 200-300 vertical feet. D1 in size. These avalanches are easy to avoid as they are starting quite small and narrow and only gaining harmful momentum mid to lower track as the terrain funnels and confines the debris.

Weather: Amazingly pleasant. Sunny skies, calm winds, temps in valley around 10F to start with 11K temps near or above freezing.

Snowpack: Toured primarily E-N aspects up to 11,600′ paying close attention to near surface conditions and any Loose Dry avalanche concerns in the Northwest zone.  Snowpack depths are 40-60 cm with the upper 15-20 cm heavily faceted. Below 10,500′ its trap door with faceted snow or weak crusts/facets to ground. Moving above 10,500′ and into more open terrain, there is generally a meager 1F midpack offering ski support and a shallow bed surface for any Loose activity. The upper 15-20 cm is faceted similar to lower elevations however.

Stomped on a few N/NE near tree line features with October facets(3mm) near the ground with no cracking or signs of instability. Slabs are not present across terrain features.

 

Photos:

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Zone: Northwest Mountains

Location: North Pole Basin

Date of Observation: 12/05/2020

Name: Ben Pritchett

 

Subject: Schofield area

Aspect:

Elevation: Above treeline

Avalanches:

Mid morning we watched a few cinnamon rolls come out of southeast facing cliffs.

Weather: Warm and calm.

Snowpack: We found highly variable, soft wind-textured snow surfaces. Average snowpack depth ranged from one and half feet on east to south facing slopes, with and average just over two feet deep on north to east-facing slopes. The snowpack remains essentially right-side-up, with denser stiffer snow near the ground and weaker faceted snow near the snow surface. Ski penetration averaged ~4 to 6 inches deep. In shallowly snow-coved wind-swept areas the snowpack was less supportive with ski penetration to the ground.

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