23-24

This avalanche was triggered by riders a few days ago. This was a small slope and broke 100' wide and 2-3' deep. Photo: GNFAC 

We rode into Yale Creek today. At the head of the creek, we stopped and dug on a south-facing slope at 9000'. We found 30" of new snow that has fallen over the last week on top of an already unstable snowpack. From here we continued up Yale Creek and on a small NE-facing slope, we saw an avalanche that was triggered by snowmobilers within the last couple of days. This avalanche was 2-3' deep and 100 feet wide and failed on weak faceted snow near the ground. It did not run far vertically because it was such a small slope. We dug near here on a SE facing slope and saw a similar setup as earlier with 30"+ of new snow overlaying weak snow. 

On our way out, we saw a small freshly triggered avalanche. This was in a small gully and failed on weak snow near the ground 1-2' deep. With poor visibility, we did not get an opportunity to see any avalanches on larger slopes. However, seeing avalanches on small protected slopes is a good indicator that there are likely avalanches on larger steep slopes we could not see. 

Wind was calm to light out of the south and snow continued through the day, with 1-2" of snow falling while we rode. 

Dug a very quick pit on a SE slope at 9600ft HS 90 cm. Boot pen to the ground. SKY OVC. Wind L. 

Visibility was minimal, but I observed no signs of significant, recent wind loading. With that said there is a ~5-8 cm (small) 1F wind slab under ~5cm of + at the top of the snowpack and above the Jan. crust.

ECTN26 below the Jan. crust

PST 30/100 End on 2-3mm facets down ~50cm (below the jan crust)

Where the crust exist, it may be ever so slightly harder to impact these deeper, weaker layers, but I would certainly not place any faith in it especially with spacial variability and change in aspect/elevation.

After doing the ECT and not observing any propagation. I pulled the block off with my shovel and it broke deeper (Q1/2) on the same facets I performed the PST on. 

I dug in this same meadow earlier in the winter. Basal facets/ depth hoar have advanced significantly. I didn't put them on a card,but striations were visible to the naked eye.

This snowpack has a lot going on in  it, but strength is certainly not one of them. Out of the entire snowpack maybe only 10-15cm of snow had hand hardness greater than 4F+.

Cracking about 20ft long observed during our tour when crossing over a gully/stream at 35 degree slope angle. Crust about 25-30 centimeters below soft snow showed instability along with the faceted base toward the bottom of the snowpack.

Natural avalanche on East Side of Henderson Mtn. seen late on 2/7/24. South of the two that Doug saw last week, along the ridge. Could have happened yesterday or last night. I didn’t see it yesterday when riding up and down Fisher creek, but visibility was mediocre. The debris and bed had at least some new snow on it. Photo: GNFAC

AVALANCHE WARNING for Island Park, Lionhead, S. Madison, S. Gallatin

Wx @ 0600