CNFAIC LogoCNFAIC Logo

Observations

Region: Summit
Location: Tenderfoot
Observer:
Date:

Route & General Observations

Toured up Tenderfoot ridge to 3100′. Facetting surface snow over a stout crust made for good meadow skiing. Snow conditions at/above tree line were a variable mix of sastrugi, windboard, anti-tracks and wind slabs due to the north winds. Our main goals for the day: 1) determine how the surface snow was bonding to the rain crust immediately below and 2) determine the reactivity of the basal facets in the snowpack in the alpine.

Red Flags

Obvious signs of instability

Recent Avalanches?NoCollapsing (Whumphing)?NoCracking (Shooting cracks)?Yes

Observer Comments

Likely older wind slab avalanches observed on S aspects of Butch Peak below corniced ridgelines, appeared to be naturally occurring. Active pluming on surrounding peaks due to gusty N winds, and moderate wind loading on leeward (south) aspects on Tenderfoot.

Weather

Weather

11:00am - Summit Snotel @ 1400' - 26*F, partly sunny, calm winds
2:30pm - Tenderfoot ridge @ 3000' - partly sunny, N winds gusting from calm to 30 mph

Snow Characteristics

Snow surface

Below treeline: 4-6" of facetting snow sitting on a stout ice crust. This facetted snow showed poor bonding to ice crust below, as evidenced by difficult skinning and shovel tilt tests.

At treeline: wind effect very present at treeline, with variable conditions ranging from pockets of soft snow to windboard to windslabs on S aspects.

Alpine: Variable conditions based on aspect. Conditions changed from small slabby pockets on the northerly aspects to stripped sastrugi/anti tracks on westerly aspects to ~1'+wind slabs on southerly aspects due to the N wind. Any loose snow above ~2500' has been transported by the wind.

Snowpack

Below treeline: hand pits indicated a multitude of different supportable crusts within the snowpack

Alpine: Snowpack depth varied greatly based on aspect. At 3100', N aspects depth ranged from 70-100cm, stripped to ground along ridgelines, and S aspects ranged from 180-200cm.
We dug one pit at 3100', N aspect, 30* slope, HS 70cm. See picture below for pit composition.
Pit results:
1 compression test: CT11SP down 60cm at melt freeze/basal facet interface
2 extended column tests: 1st: ECTX. 2nd: ECTP 25 down 65cm within basal facets (depth hoar/basal facet transition). Note that the depth hoar crystals in which the ECT failed upon were cupped and 3-4mm in size

Photos & Video

Photos



USFS SNOW AND AVALANCHE HOTLINE (907) 754-2369
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
© 2018 Chugach National Forest Avalanche Information Center. All rights reserved.
FCNFAIC
Donate
If you think a public avalanche
center is important then we urge
you to become a member & donate.


PickClickGive