Pro Field Report

Basic Information

Observation Details

Observation Date:
December 26, 2021
Submitted:
December 26, 2021
Observer:
SAC - Scott Savage - OFF DUTY REC DAY
Zone or Region:
Galena Summit and Eastern Mtns
Location:
Galena Summit - Cross (E-SE, a little bit of NE: 8400-9200')

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
None Experienced
Saw several small, shallow, narrow (less than 40' wide) D1-1.5 natural slides in the foothills from Hailey-Greenhorn/East Fork turn-off. E and W aspects, predominantly in wind-affected terrain but not true wind slab avalanches. Several were fresh and happened late this morning. The cracking I experienced was at ridgeline near 9200', relatively shallow (10-15cm), and did not travel very far.

Bottom Line

No obvious signs of instability in terrain lacking the old October faceted snow, but impressive amounts of new snowfall. Obvious wind effects at/near ridgelines at the higher end of middle elevation terrain. Mid-storm and pre-storm instabilities were not much of a concern in this particular location this afternoon.

Advanced Information

Weather Summary

Cloud Cover:
Obscured
Temperature:
Single digits F
Wind:
Light , SW
New/Recent Snowfall:
HN=12-18" (30-45cm) of low density snowfall since yesterday afternoon? settled HST=~24-36" (65-85cm)

Mostly S1 while we were out from 1-3:30 PM. Winds were light, gusting moderate, and erratic/inconsistent. Previous wind-loading at exposed ridgelines with some variable wind-stiffening in upper 10 cm in treeless terrain up to 300' vertical below ridgeline, but not much in the way of true wind slabs. Not much active wind transport at this location while we were out. An impressive amount of low-density snow is available for transport.

Snowpack Observations

No formal snowpits, recreational day. Just probing, pole probing, and hand pits/tests.
HS=130-165cm
Storm snow comprises the upper half of the snowpack (65-85cm)
Top 30-45cm=F low density PP Ski Pen=up to 45cm
Mid-storm interface between lower density HN24 and denser 4F>>1F storm snow: could be an issue in very steep terrain and especially where wind loaded/stiffened. This is a non-descript, subtle layer that should be short-lived.
Denser settling storm snow=4F>>1F PP/DF to about 60-80cm above the ground depending on snowpack depth
12/19-22 crusts or facets were not easily identifiable here, but there is a 5cm thick layer at the interface between the current storm and the mid-Dec storm. Probably need to be in steeper W-SW-S-SE to see better-developed crusts/FC (given the sun's low angle of incidence when this layer/layers formed).
Below that=mid-December storm snow, not directly observed but did not feel any Oct snow near the ground while probing. Generally well-graded snowpack increasing in hardness with depth.

Avalanche Problems

These comments only apply to slopes WITHOUT old October snow: No real avalanche problem where we traveled. An increase in wind-loading could easily create a wind slab problem and possibly a persistent slab problem. The snowpack where we traveled generally lacked stiffness at the surface; I would be wondering about persistent issues with 12/19-22 on steep solar slopes (>35*) with more of a slab at the surface.

Terrain Use

To keep things simple, we chose a location where it was easy to stay out of all avalanche terrain. Upper elevations and all shady slopes that could have old Oct snow at the base of the snowpack were off-limits no matter where we would have gone. We would have felt comfortable today in non-wind loaded terrain up to about 35* where Oct snow did not exist, but we stuck with our plan and stayed out of all avalanche terrain.