Pro Field Report
Basic Information
Observation Details
Observation Date:
January 11, 2020Submitted:
January 11, 2020Observer:
SAC - LundyZone or Region:
Banner SummitLocation:
Copper MtnSigns of Unstable Snow
Recent Avalanches?
None ObservedCracking?
IsolatedCollapsing?
None ExperiencedSnow Stability
Stability Rating:
FairConfidence in Rating:
ModerateStability Trend:
WorseningBottom Line
Main stability issue was fresh wind slabs - the moderate west winds were transporting lots of the low density new snow and forming sensitive drifts at the top. Persistent weak layers in this area were more than 3 feet deep in most spots, and over 4 feet in some. Especially with additional snowfall coming, we are trending towards a deep slab problem in our deeper snowpack areas in the Banner Summit and Sawtooth/W Smoky zones.
Media/Attachments
Advanced Information
Weather Summary
Cloud Cover:
ObscuredTemperature:
n/oWind:
Moderate , WStorm day. S1-2 during my short tour from 11:30-15:00. 4-5cm fell while I was out, with the storm total around 30cm. Snow was around 6-7%. Light winds in exposed mid elevations, and steady moderate winds at ridge level. Drifting was significant at the summit. Snowfall lessened as you came back towards Stanley.
Snowpack Observations
At low and mid elevations, the primary weak layer is the 12/31 layer which is the top of the thin/faceted snowpack that existed before the new year. It looked worse on shady slopes, but didn't look terrible on either solar or shady aspects. There does not seem to be any prominent weak layers above the 12/31 interface.
@7300', SW: HS 120cm. ECTX on 12/31. Facets were 4F. Decent looking snowpack overall. 12/31 facets on a NW aspect near this location were a bit weaker (F+/4F-) but did not break cleanly during a hand shear.
@8100, W, 22*: HS 155cm. ECTNs in the top 100cm, but nothing dramatic. The 12/31 interface could not be located. 12/7 SH was present but very faint and 120cm down - see photo. Main weak layer was the 11/26 FC on top of a crust above welding DH - this was 135cm down. A non-standard deep ECT just above the deeper layers produced an ECTP21 on 11l/26.
Avalanche Problems
| Problem | Location | Distribution | Sensitivity | Size | Comments |
|---|---|---|---|---|---|
Wind Slab
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Layer Depth/Date: 30-80cm, today Comments: See photo below. Both stiff and soft drifts were present. Where I could stomp them safely, they seemed touchy. |
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Persistent Slab
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Layer Depth/Date: 12/7: 120cm, 11/26:135+cm Comments: The older weak layers are trending towards a deep slab problem and becoming hard to trigger. Based on limited data, the SH layer seems to be less of a concern than the basal DH. |
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Persistent Slab
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Layer Depth/Date: 12/31: 80-100cm. Comments: I didn't specifically observe the lower elevations but I suspect it exists there as well. The 12/31 facets don't seem particularly bad. I didn't see anywhere where a crusts exists at the 12/31 interface, but that could make it more reactive. |
Terrain Use
Mindset was stepping back and I avoided avalanche terrain. This may have been a bit conservative based on what I saw, but I certainly would have kept it in the low 30s and under, and avoided any wind loaded slope.