Avalanche: Hatcher Pass

Location: Marmot

Date:
Observer:
Route & General Observations

Skinned up the SW ridge of Marmot, skied down the mid rib, skinned up mid rib, and skied down Rae Wallace Chutes. Several human triggered slab, cornice, wet loose, and dry loose avalanches observed across Hatcher Pass. Several natural long-running loose dry and wet loose avalanches observed during our tour. Strong sun affect in the afternoon.

Contact, Location & General Observations
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Forecaster Comments

Observations: Several days of wind, gusting E/SE 22-44 mph built wind slabs that were reactive 3/8 and 3/9. Slabs are becoming less reactive. 9" of new snow is covering slabs formed 3/8-3/9. It is still POSSIBLE to human trigger a soft slab 6-12" thick on SW through NE aspects on slopes above 35 deg at mid and upper elevation. Dry loose and wet loose could be larger than you think and funnel you somewhere you don't want to go, like a terrain trap.

Avalanche Details
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Trigger NaturalAvalanche Type Unknown
Aspect UnknownElevationunknown
Slope AngleunknownCrown Depthunknown
WidthunknownVertical Rununknown
Avalanche Details

Several human triggered avalanches today:
- 4 small (D1) persistent soft slab avalanches, 4500', 6-12 inches deep, on steep SW to W aspects of spines of Rae Wallace Chutes
- 2 larger (D1.5 to D2) slab avalanches, 3000-3500', estimated 6-12" deep on NW aspect of Arkose (Punk Spines ,due N of Stairstep), one of which looked to have sympathetically triggered another small slab avalanche below.
- Intentional skier triggered cornice triggering long running loose dry on SW aspect of Marmot N of mid rib
- Human triggered long running wet loose on SW aspect near weather station
- Intentional skier triggered cornice in Rae Wallace triggering long running dry loose; and several long running dry loose in Rae Wallace.

Natural avalanches observed during the tour:
- Long running dry loose on NE/E aspect of Skyscraper,4500', that ran from ridge into Eldorado Bowl about 700 ft.
- Wet loose running long distances on SW aspect of Marmot below Rae Wallace, above 3500', in the afternoon.
- Wet loose on Idaho Peak, 3000-4000', S>SW aspects
- Small wet loose on road cut at lower elevation, below 1500'

Red Flags
Red flags are simple visual clues that are a sign of potential avalanche danger. Please record any sign of red flags below.
Obvious signs of instability
Recent Avalanches?Yes
Collapsing (Whumphing)?Yes
Cracking (Shooting cracks)?Yes
Observer Comments

In addition to the natural and human-triggered avalanches mentioned above, we had one shooting crack on our way up the SW ridge of Marmot (~3500') and a few whumphs in the same area.

The sun came out and started cooking the slopes in the afternoon, resulting in roller balls and long running wet loose in southerly steep slopes.

Lots of long running dry loose on steep (>40 degrees) S aspects of Microdot and NW aspect of Microdot Ridge.

Weather & Snow Characteristics
Please provide details to help us determine the weather and snowpack during the time this observation took place.
Weather

Few clouds to clear skies, light SE winds, no precipitation, temps in teens and 20s F

Snow surface

9" new low-density snow measured at Independence Mine this morning. Less new snow noticed in some windward southerly aspects. Great ski quality. The snow surface on southerly aspects was moistening during the day and becoming heavier and not as nice for skiing by later afternoon.

Snowpack

On southerly aspects during our tour hand pits and test pits revealed 3-12" of snow sitting over near surface facets on top of a sun crust, or a 4F to 1F wind slab over facets over a sun crust. Cornices have grown in size and are sensitive.

Pit 1: Marmot off the standard uptrack up the SW ridge, 4000', WSW, ECTPV down 40 cm with the slab breaking 2 ft past the 90 cm column we tried to isolate. The slab failed on facets above a sun crust.

Pit 2: Marmot Catcher's Mit, 4100', SW, 40 degree slope, HS=140 cm, ECTP11 down 30 cm on 1cm of 0.5-1mm facets over a sun crust. The slab on top ranged from 4F wind slab to F hard new snow.

Pit 3: Marmot, 4150', NW, ECTN20 on new old interface (on top of 4 cm sun crust).

Photos & Video
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