Avalanche: Hatcher Pass

Location:

Date:
Observer:
Route & General Observations

Independence Mine to Microdot

Avalanche Details
If this is an avalanche observation, click yes below and fill in the form as best as you can. If people were involved, please provide details.
Trigger NaturalAvalanche Type Soft Slab
Aspect South SouthwestElevation 3900ft
Slope AngleunknownCrown Depthunknown
WidthunknownVertical Rununknown
Avalanche Details

This avalanche happened between 2-3 pm. Trigger is likely to be radiant heat.

Marmot Mountain, above the Archangel Trailhead, in a large bowl feature which runs into a steep creek/terrain trap.

Avalanches on similar aspects at lower elevations (approx 3000-3500'), may have sympathetically triggered the upper elevation avalanche.

Estimated SS-Ny-D1.5-I/O, 0.5-1 feet deep, 100-200 foot wide, ran about 600 feet. The crown was located mid-slope, rocks were visible in the bed surface giving some indication of depth of weak layer.

Lower elevations avalanches SS-N-D1.5-I 0.5-1 foot deep, ~200' wide just above the creek bottom. see pics

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)?No
Observer Comments

Natural avalanche today on Marmot Mountain, SSW, 3500', D1.5, mentioned above
Whumphing in areas where new snow had been previously drifted during 2/12-2/14 [Valentines Storm], was cohesive, sitting over surface hoar and 4F facets, up to 60 cm deep.

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

Clearing in afternoon. Microdot at 4136', -6.5C, winds 0-2.3 mph Variable and East

Snow surface

At 3000'-4500' = New snow 15 cm overnight, 60cm total from 2/12 to 2/15
South Southwest aspects begining to feel the heat of the sun and form micro-crust

Snowpack

60 cm new snow, F (top) to 1F (2/12 came in with wind) / 4F 2.0mm Facets and Surface Hoar
New snow/old snow reactive in pits (PST 25/100 at SW, 4100', 1F wind slab/2.0mm facets) and producing whumphing, shooting cracks up to 15' long failing on new/old.

Photos & Video
Please upload photos below. Maximum of 5 megabytes per image. Click here for help on resizing images. If you are having trouble uploading please email images separately to staff.