Pro Field Report

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Weather Summary

The morning started clear, bands of mid and upper level clouds began amassing on the western horizon by late morning but did not really begin preventing solar radiation until 1200 or 1300. Thick clouds moved over the Sawtooths briefly (looked like it may have been flurrying?), then pulled back a bit later in the afternoon. It was snowing S-1 on my drive back south. A steady, low end of moderate S wind blew for much of the afternoon

Avalanche Observations

Snowpack Observations

My objectives were to at the snowpack in this area (I've been nearby but not on Horton), to continue the hunt for mid/upper pack weak layers (12/8 and 12/19), and to see how much it snowed and look for recent activity.

I traveled on most aspects and through the elevation bands. I found a much thinner, not terribly pretty snowpack on the W side of the hill (unsurprisingly), a relatively deep and uniform snowpack on the E side of the hill, and reactive weak layers in the mid/upper snowpack on solar slopes at middle elevation.

7500', SW, HS 70-75cm: I had one large collapse at valley bottom, then continued up to this slope which also produced a large collapse. I stop and dug down to find our old friend 11/27 producing the collapses. This slope had a few thin, icy crusts at 12/8 and 12/19, and a strong 2-3cm crust beneath the new snow with 10-12cm of low density snow on top. 11/27 is down 60-65cm presented as 2-3.5mm facets with cups and striations. These are some of the larger facets I've seen here. There was a bit of moisture at the ground but the upper interval of 11/27 was dry. This layer produced ECTP 4, 7, and 12.

9200', ENE, HS 130-140cm: Snowpack looked considerably different on this sheltered ENE aspect. It was fairly difficult to distinguish individual layers visually, with the exception of 11/27 which was down 105-110cm. This produced ECTNs with non-standard loading steps, something like 33-35. I did a single CPST and didn't feel like I did a great job with the saw, CPST 40/110 END. In places, we are trending in the right direction with this layer, but it would be a clear mistake to take it off the problem list now. Where conditions are favorable (deeper snowpack, gentler gradients, more weight for crushing) this layer is very gradually healing. Where the snowpack is thinner/colder and the overlying slab is thinner this layer is not getting better (see 12/26 White Clouds remote triggered D2.5...). In this pit, neither 12/8 nor 12/19 produced unstable snowpack test scores.

9300', SSE, HS 90-95cm: I've been hunting these pesky mid-pack weak layers for the last week to 10 days, I'm growing increasingly confident that they are most problematic on solars where they present as a MFcr+FC. I am also suspicious of them where they present as standing SH, but the distribution on this seems to be fairly isolated, or maybe I'm just looking in the wrong places. I dug this pit looking for the MFcr+FC combos and found them. Both layers had a subtle (faceted) crust with small facets above. These produced ECTPs in all of my tests. 12/19: ECTP 12, 14, and 16 down 35-40cm. 12/8: ECTP 20, 21 down 50-55cm. As I stepped out of my pit onto my pit debris I managed to collapse the slope, likely on one of these layers. 11/27 was not terribly distinct here, there were some larger facets that were now well on there way to rounding and bonding to the icy crust that sat below and was glued to the ground. This entire package came out as a unit while digging.

We are on the road to recovery with the 11/27 weak layer, but we have a lot of road left in front of us. As we travel the road, the snowpack is becoming more complex for a backcountry traveler: there are slopes where triggering a slide is unlikely, but plenty of slopes where triggering one remains likely, and all shades of grey in between. This is an easy time to get caught with one's proverbial pants down.

Avalanche Problems

Problem	Location	Distribution	Sensitivity	Size	Comments
Persistent Slab	N E S W	Isolated Specific Widespread	Unreactive Stubborn Reactive Touchy	D1 D1.5 D2 D2.5 D3 D3.5 D4 D4.5 D5	Weak Layer(s): Dec 19, 2022 (FC) Dec 8, 2022 (FCsf) Comments: These layers seem to be showing a pattern of being at their worst where MFcr+FC combos exist. They have also produced avalanches on shady slopes as well, where standing SH was present, and I'm not ignoring them there.
Deep Persistent Slab	N E S W	Isolated Specific Widespread	Unreactive Stubborn Reactive Touchy	D1 D1.5 D2 D2.5 D3 D3.5 D4 D4.5 D5	Weak Layer(s): Nov 27, 2022 (FC) Comments: Distribution of the 11/27 problem is trending towards specific. In places where we are burying it deeply it is having time to heal, very gradually. In places where the snowpack has remained thin, the weak layer is not improving.