Pro Field Report
Basic Information
Observation Details
Observation Date:
December 12, 2022Submitted:
December 12, 2022Observer:
SAC - Chris Lundy, Tanner HaskinsZone or Region:
Banner SummitLocation:
Langer (7100-8700', SW-S-E-NE)Signs of Unstable Snow
Recent Avalanches?
YesCracking?
None ExperiencedCollapsing?
IsolatedSnow Stability
Stability Rating:
FairConfidence in Rating:
ModerateStability Trend:
SteadyBottom Line
The November weak layer is buried beneath a 2.5-3' thick, dense slab in this area. Snowpits revealed a very poor snowpack structure and yielded unstable results. We're trending towards a deep slab problem in this zone, with avalanches becoming more difficult to trigger but with high consequences. Bouts of moderate NE winds were transporting snow and creating fresh wind slabs.
Advanced Information
Weather Summary
Cloud Cover:
OvercastWind:
Moderate , NENew/Recent Snowfall:
Settled HST since 12/8 seemed to be ~45cmPartial clearing threatened around noon, but then it socked back in and the wind increased from the NE. The wind was intermittent, but blowing at moderate speeds and moving snow.
Avalanche Observations
| # | Date | Location | Size | Type | Bed Sfc | Depth | Trigger | Photos | Details |
|---|---|---|---|---|---|---|---|---|---|
| 2 |
Dec 11, 2022 (+/- 1 day) |
Across from the Stanley RS W 7200ft |
D1.5 | SS-Soft Slab | N-Natural |
|
Report |
We had fairly poor light and didn't get good eyes on much terrain, but we did not see avalanche activity on the few slopes we did see. Given the flat light and that crowns may be partially filled in, we easily could have missed some.
Snowpack Observations
Riding off trail at lower elevations, I observed the snow falling out of trees 30-50' ahead of me - I'm almost positive this was due to collapsing. We had only isolated collapsing once we climbed off the valley floor - likely due to the increasing slab depth and stiffness.
@7100', flat: HS 105cm. Slab depth by probing was around 75cm down to 11/27. We confirmed this measurement by burying the track of one sled.
Found a very thin crust at the 12/8 interface 45cm down on one low elevation solar slope. In other pits, we could not find any sign of 12/8.
@7800', S: HS 130cm. 11/27 down 90cm. 11/27 presented as 4F FC below a 4cm K MFcr. ECTX but got a P result with nonstandard force, failing below the crust.
@8300', E: HS 120cm. 11/27 down 90cm. 11/27 was a thin layer of 4F FC. ECTP13 which was a bit alarming for such a thick/hard slab.
In both pits, the weak layer was buried beneath a stiff slab, with the bottom half P to 1F atop a soft 4F weak layer.
Avalanche Problems
| Problem | Location | Distribution | Sensitivity | Size | Comments |
|---|---|---|---|---|---|
Persistent Slab
|
|
Layer Depth/Date: 75-90cm Weak Layer(s): Nov 27, 2022 (FC) Comments: Weak layer looks the worst on shady slopes, and that's where we received the worst test results. Solars still look suspect though. Trending towards a deep slab problem. |
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Wind Slab
|
|
Layer Depth/Date: 20-40cm Comments: NE winds were moving snow today, creating fresh slabs and drifts. The terrain we were in wasn't conducive to estimating sensitivity, but I would have been even more concerned about freshly loaded slopes. |
With little sign of a 12/8 weak layer or other poor interface, storm slabs did not seem to be an issue.
Terrain Use
We avoided avalanche terrain.