Northern Gallatin

A skier triggered an avalanche on the SE face of Mt. Blackmore near the ridge on the morning of 1/19/24.

From text:  "Hard to with the visibility but it ran almost all the way to the skin track (~800 vertical). It definitely broke 8 inches deep and 50 ft wide, but it might've gotten a little wider and deeper."

From obs: "About 50' from our pit we remotely triggered two D1 slab avalanches which broke on the roll over 150' above us. Crowns looked between 1-2' and 20-30' wide. The larger of the two ran 100' more or less." Photo: S. Lowe

From obs: "About 50' from our pit we remotely triggered two D1 slab avalanches which broke on the roll over 150' above us. Crowns looked between 1-2' and 20-30' wide." Photo: S. Lowe

Was attempting to find a few small safe powder pockets up in hyalite today. Was pretty unsuccessful, collapsing was happening the entire ski up but didn’t seem to be super unstable. Soon as I got the some open low angel area I had a major collapse probably 50 foot circle around me that was very loud. At this point I turned around. Snow was very different depths all the way up. Areas I could put my poles (110) almost under the snow other places the snow was only inches. Also noted a hard layer about 6 inches down that was good snow with light powder on top and sugar underneath. 
 

(Was skining up the road to the strip east of the peak.)

We skinned up towards Hyalite peak today to see how the snowpack was adjusting to this new load. While we did see some point release on the canyon walls during our approach, there was no collapsing and minimal wind effect below 9000 feet. As soon as we topped out into the hyalite lake basin, a northerly wind picked up and there were supportable wind drifts scatted about. Got an ECTx on a northern aspect at 9200' before deciding to ascend a 25 degree adjacent slope. About 50' from our pit we remotely triggered two D1 slab avalanches which broke on the roll over 150' above us. Crowns looked between 1-2' and 20-30' wide. The larger of the two ran 100' more or less. Yikes, time to bail! The low angle tree skiing along the skinner was quite nice.

Moderate to Strong, SW winds were picking up this evening at Lick Creek, resulting in moderate snow transport along the ground. Previous drifts were building in leeward aspects and small terrain features, and I noted several areas of very dense wind board while skiing and touring. I also observed some local collapsing of these wind slabs around my skis, and would expect this issue to be exacerbated higher elevations by increased wind transport and the widespread presence of pwls. I was surprised by the amount of snow available for transport, especially at the relatively low elevation, and was glad to be in simple, low-angle, terrain.

On my tour up the main fork of Hyalite today I noticed two slides near Divide Peak caused by wind loading.  There was a wind skim on all snow surfaces in the Basin and I experiences a bit of collapsing while walking across the basin in the flats on small wind loaded pockets

We toured into Mount Blackmore and up the standard route on the southeast-facing shoulder. Winds at higher elevations resulted in some drifting and there were pillows of recently drifted snow evident on the east face of Blackmore. We did not experience any collapsing, shooting cracks, or obvious signs of instability on our tour.

We dug at the top of the shoulder with unremarkable results (ECTN5 5" below the surface on a hardness change). The structure is very weak but it lacks a cohesive slab in many areas to push it over the edge toward instability. It is possible to trigger an avalanche on slopes with recent wind-drifting or where a thicker slab is resting on persistent weak layers. Avoid wind-loaded slopes and you will minimize the chances of finding a trigger-point. 

With snow on the way, we expect to see the danger rise in the coming days. Recent avalanche activity, collapsing, and shooting cracks are all reasons to chose travel on slopes less than 30 degrees in steepness.