Pro Field Report
Basic Information
Observation Details
Observation Date:
February 5, 2020Submitted:
February 5, 2020Observer:
SAC - Martin StefanZone or Region:
Galena Summit and Eastern MtnsLocation:
South of Gladiator ckSigns of Unstable Snow
Recent Avalanches?
YesCracking?
IsolatedCollapsing?
None ExperiencedSnow Stability
Stability Rating:
PoorConfidence in Rating:
HighStability Trend:
ImprovingBottom Line
Went to investigate crown on avalanche from S side of Gladiator. It failed on a layer of facets buried under a stiff wind slab that most likely got overloaded during the wind event on Monday 2/3.
On the way up the ridge line, I spotted a fresh D1.5 avalanche down the south face of the ridge line and fresh wind drifts on leeward slopes were reactive and easy to trigger. Wind has now blown both from NE and NW with a bit of snowfall thrown into the mix, making wind loading patterns more complex to deal with.
Media/Attachments
Advanced Information
Weather Summary
Cloud Cover:
OvercastWind:
Moderate , NWBreezy up high, mostly overcast and S-1 to S1 all day. Lots of wind transport at higher elevations, loading S-SE faces. Hard to gauge accumulation up high due to wind, down at hwy level 2-3" by 3pm.
Avalanche Observations
| # | Date | Location | Size | Type | Bed Sfc | Depth | Trigger | Comments | Photo |
|---|---|---|---|---|---|---|---|---|---|
| 1 |
S of Gladiator Ck S 9600' |
D1.5 | SS | S-New Snow | 20cm | N-Natural | Crown depth tapers from 10 to 40 cm, looked like it slid the full path but low confidence due to bad visibility. Judging by the rate of wind loading and how crisp the crown was, I don't think it was more than a couple of hours old. |
|
|
| 1 |
Start zone S of Gladiator ck, west of earlier slide SW 10000' |
HS | O-Old Snow | 15cm (?) | N-Natural | The other half of the starting zone I went to investigate had slid sometime between yesterday afternoon and noon today, the area circled in the picture (taken yesterday). Slab was probably very thin and visibility was hit and miss, but I am fairly confident the northern half of the starting zone was gauged down to the same bed surface as the original slid, first observed on Monday. |
|
Snowpack Observations
Crown of original avalanche between 1,5m and 50cm, P-K hard. Failure layer is a 3cm thick layer of small facets, 4f hard, sandwiched between the hard slab and a K hard bed surface. The weak layer is continous along the whole crown, and my guess is that it got overloaded by wind drifted snow where the slab is thinner and propagated across, as opposed to being triggered by a cornice drop where the crown was thickest, but confidence not very high on that guess.
Crown in the first of the lower pockets on lookers right that got ripped out was thinner, around 30cm tapering down to under 20cm, HS approx 90cm. No results on ECT, PST55/100end
In the track 10-15m below crown HS around 20cm with rocks poking through in places. Mostly K hard wind crust around 10cm thick with well developed, stirated and sometimes chained DH below.
Lots of wind loading along ridge created touchy soft slabs, below approx 8600' a zipper crust could be felt under the new snow when nibbling on S side of ridge.
Avalanche Problems
| Problem | Location | Distribution | Sensitivity | Size | Comments |
|---|---|---|---|---|---|
Wind Slab
|
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Layer Depth/Date: 10-50cm, 2/5 and 2/3 Comments: Wind from both NW and previously NE makes loading patterns complex. |
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Persistent Slab
|
|
Unknown |
Layer Depth/Date: 20-100cm, weak snow near the ground or mid-pack Comments: It is clear that these layers are still in the mix, especially if loaded by fresh wind slabs. I did not perform any tests today, but the one fresh slide on an S aspect did not look like it stepped down. On the other hand, the thin snow on the lookers left of the starting zone seemed to have failed recently on persistent grains. |
Terrain Use
I avoided avalanche terrain including overhead hazard except for the bed surface in close proximity to crowns.