Northern Gallatin

We skied the ridge north of Blackmore (Tomahawk Ridge?) traveling between 6800' -9200' on SE-NE aspects. We dug two pits. one at 8000' on a NE aspect, HS 170cm fair structure, good strength. ECTN24 @ 45cm below the surface. With loupe and card I could find a few SH feathers on the failure plain. 

Second Pit. 9200', NE, previously loaded. HS 210. ECTN28@ -40cm. similar structure but bed surface was much harder (P) old wind board. Couldn't find any surface hoar but found .5mm NSF on failure plain. 

On the ridge above, ~9400' on a NE aspect there was a natural avalanche, maybe cornice failure, probably same timeframe as the Divide slides. ran ~600'.

HS-N-D2-R2-O

Wide spread surface hoar on top this morning. Sun was knocking it down on solar slopes by 11:30. Snow (S1) started at ~12:15 

I went for a walk up to divide basin today and noticed two slides that occurred on high, steep, north facing slopes last night (Tuesday night) when the wind picked up 

I went for a walk up to divide basin today and noticed two slides that occurred on high, steep, north facing slopes last night (Tuesday night) when the wind picked up 

We toured into Hyalite Peak to investigate a large, skier-triggered avalanche that occurred on Saturday (avalanche details and photos). The avalanche broke 750' wide, ran 650' vertical and broke 3-5' deep. It failed on a layer of sugary facets buried 95 cm (3 feet) deep. This layer had not been producing avalanche in the weeks prior to this slide. We measured 8.3" of snow water equivalent contained in the slab overlying the weak layer. We tested the weak layer in the eastern most part of the crown and got an ECTP26.

Additionally, we found a very weak layer of facets and surface hoar buried 1-1.5 feet deep. This had nothing to do with the large avalanche. The party reported triggering some small wind slabs near the summit, these may have been related but we don't know for sure. This layer failed with at ECTP13 and ECTP20. We looked for it again on our exit from the basin and came up empty. It is certainly something that we will look for in the coming weeks, but the primary driver of our decision-making will remain the deeper instability for now. 

While investigating an avalanche that failed on a weak layer of facets buried in January, we notice a new layer that we will be looking for and testing as we move forward. Photo: GNFAC

Investigating a recent avalanche on Hyalite Peak. Photo: GNFAC