Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
March 24, 2020
Submitted:
March 24, 2020
Observer:
SAC - Savage
Zone or Region:
Banner Summit
Location:
Copper Mtn: 6900-9000', N-W-S aspects

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Isolated
Collapsing? 
None Experienced
Isolated cracking in upper elevation drifts - all cracks less than 10' wide.

Snow Stability

Stability Rating: 
Good
Confidence in Rating: 
High
Stability Trend: 

Bottom Line

Intermittent, gusty winds formed isolated 10-14" thick wind slabs at/near ridgelines above about 8500'. There were a few potential failure layers within the new snow, but these should "heal" fairly quickly (hours to days). Failures at the old/new interface and on a layer of dirty, facets from early March could take longer to fully stabilize. The lower elevations crusts below the new snow are still damp or moist and will probably present wet loose problems (the new storm snow sliding on the old crust) with even minimal sun tomorrow.

Advanced Information

Weather Summary

Cloud Cover:
Obscured
Temperature:
teens and 20s F
Wind:
Moderate , S

8-10" (20-25cm) new snow with about half of that falling during the day today. The snow was generally "right side up" with lower density snow on top of denser snow from the beginning of the storm. S-SW winds varied from light to moderate and were both gusty and intermittent; the skin track was gone above about 8500'. It was still snowing fairly hard (S2-3) when I left around 6 PM.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Comments Photo

None

Snowpack Observations

8-10" (15-20cm) new snow by 5 PM, well graded with light on top of dense.
Below 7500': old crust was still moist on W aspects, giving the new snow a "greasy" feel at the interface. It was almost ready to move as small WL slides on very steep slopes, but it wasn't quite there yet.
7500-8500': Not much going on - no/very few wind slabs, old crust was frozen on W and SW, and old crust was textured. The storm snow seemed to be bonding pretty well to the old interface.
Above 8500': Isolated wind-slabs on NW-N-NE (I didn't get a look at E aspects) at and just below ridgeline. Easiest failures were thin, very soft 10-20cm slabs (4-8" thick) formed in the lower density snow from today, failing on weaknesses within the new snow. Where slabs were stiff near the summit, some cracking on slopes <32* at old/new interface.
Stability tests: N, 8950' near summit in windloaded area: CT6-12 on layers within the new snow (Q1-2) and on dirty FC layer (Q1): ECTN4, ECTN6 on the new snow instabilities and ECTN13 on the dirty facets 45cm down.

(3-24-20) Snowpit on a wind-loaded slope near the top of Copper Mtn.
(3-24-20) Pit showing failure layers within the new snow and at the old/new interface near the top of Copper Mtn.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Wind Slab
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
Layer Depth/Date: 3-24-20: very soft 10-20cm (4-8") of lower density wind-blown snow on top of denser new snow, a few 20-35cm stiffer slabs involving the denser storm snow

No wet loose problem today, but it's coming soon.

Terrain Use

I avoided wind-loaded starting zones and very steep, consequential lower elevation starting zones in the late afternoon.