I did not observe any hard signs of instability like cracking or collapsing. I didn't receive propagating results in snowpack tests. All that said... on shaded slopes the snowpack structure is poor. The slab is thin enough (<1 m) that triggering a large and dangerous slab avalanche remains a possibility.
The sky was blue overhead all day. There was a thick bank of mid-elevation clouds lapping at the crest of the Pioneers from the Copper Basin side. There was also a Snake Plain inversion cloud bank. There is a moderate amount of snow available for transport with a strong NW or N wind event. The other aspects were either heavily winded or cooked down by the sun.
Mar 10, 2023
(+/- 1 day)
Mar 10, 2023
(+/- 1 day)
East Fork near Federal Gulch CG
I set out to find slab thickness and weak layer character at middle elevations in an area where I knew the weak layers were ugly and where I figured the slab would be relatively thin (<1 m). I walked off the ridge in undisturbed snow on S-SE-E aspects as well as many NW-N-NE aspects and did not observe any collapses or cracking. There are pictures of two middle elevation pits (N and NW) in the media shown above.
On W-SW-S-SE aspects, the "slab" above the February facet layer is mostly riddled with crusts and ranges from only 35-50 cm thick.
The picture changes quickly as you head north of WNW or north of E. The slab on these aspects is anywhere from 50-85 cm thick and very dense (P) in the lower half. These shaded aspects yielded multiple ECTXs. Propagation did occur but only after an additional 10 and 17 hits from the shoulder. This setup was concerning but seemed unlikely to trigger due to the stiffness at the base of the slab. I imagine there are some aspects and slope angles on the margins where the conditions are "just right" (slab thickness, weak layer etc) but it seems like this would be a narrow wedge of the compass.
Layer Depth/Date: 50-80 cm
Weak Layer(s): Feb 18, 2023 (FCsf)
Comments: Shaded where observed. Triggering a persistent slab avalanche seemed unlikely on middle elevation W-SW-S-SE.
There was no obvious sign of recent wind loading. Wet avalanches were not a concern. There was not enough HST to cause an issue above the (3/19) crust. Still, given the time of year I would have been cautious on sunnier slopes this afternoon anywhere that the snowpack is thin and rotten.
I avoided avalanche terrain. I would have entered avalanche terrain on W-SW-S-SE below 8,500' with a partner.