Pro Field Report

Basic Information

Observation Details

Observation Date:
January 19, 2021
Submitted:
January 20, 2021
Observer:
SAC - VandenBos
Zone or Region:
Galena Summit and Eastern Mtns
Location:
Fourth of July Drainage (6,800-10,700')

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Isolated
Collapsing? 
Isolated
Isolated, short cracking in fresh wind drifts. Experienced a single collapse in sheltered, shaded terrain at 9,500'. Suspect there were quite a few more but didn't feel them on the sled.

Advanced Information

Weather Summary

Cloud Cover:
Clear
Wind:
Light , NW

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
1 Jan 13, 2021
(+/- 1 day) 		Fourth of July
W 10000ft 		D2.5 O-Old Snow N-Natural
Slab avalanche that failed during our last storm near the 4th of July Creek Drainage in the White Clouds.
Report
3 Jan 13, 2021
(+/- 1 day) 		Fourth of July
E ft 		D3 O-Old Snow N-Natural
Slab avalanche that failed during our last storm near the 4th of July Creek Drainage in the White Clouds.
Slab avalanches that failed during our last storm near the 4th of July Creek Drainage in the White Clouds.
Slab avalanche that failed during our last storm near the 4th of July Creek Drainage in the White Clouds.
Report
Link
12 Jan 13, 2021
(+/- 1 day) 		Fourth of July
N ft 		D2 I-New/Old Interface 1.5ft N-Natural
Slab avalanche that failed during our last storm near the 4th of July Creek Drainage in the White Clouds.
Slab avalanche that failed during our last storm near the 4th of July Creek Drainage in the White Clouds.
Report
Fourth of July
Fourth of July
Fourth of July

Widespread activity on middle elevation shadies and on all aspects at upper elevations during 1/13 storm.

Snowpack Observations

Dug at middle/upper transition near crest of the range, on SE and NNW. October snow is preserved here (on shadies). A very thin, zippery rain crust exists up to almost 10,000'. I'm not sure if this is from 1/13 or 1/17. Hunch would be 1/17, based on earlier observations of 1/13 rain crust topping out around 7,800-8,000'. I didn't find this crust the day before in Banner area, will continue to hunt for it across region.

NNW at 9,500': HS=125cm. 12/11 FC down 65cm under F- to 1F slab (increasing density with depth). 12/11 presents as F FC up to 2mm. 11/17 is 35cm off ground, 4F decomposed MFcr. 10cm of cupped, striated DH xtals (dry), 4-6mm. ECTNs with hard force on 12/11, CPST 23 and 30/100 END, PST 29 and 30/100 END, all on 12/11.

SE at 9,500': HS=100cm. 12/11 down 60cm under F- to 1F slab (increasing density with depth). 12/11 presents as 2-3cm decomposed MFcr capping F FC. FC are 4F and moist at ground. ECTP 24 and 28 on 12/11. CPST 25 and 28/100 END on 12/11. PST 29 and 32/100 END on 12/11.

Based on earlier observations and the appearance and distribution of crowns further west in the range (on shaded slopes along the drainage) I suspect there is a difference in character between the heart of the range and the foothills. Difference is driven by snow depth and slab thickness on top of 12/11.