Trip Planning for Centennial Range

We dug at 9300' off the Sawtelle Peak Road to keep tabs on stability since we put out warnings and basic information for this area. We work with the guys who manage the FAA road and they give us access for pit digging. 

The stability in this area seems generally stable. The 2 pits today tracked with our findings last week, as well as what we are seeing in nearby Lionhead. The snow is 6-7 feet with a weak layer of facets near the ground. The  facets are weak, but not unstable. With a big enough load they would be, but for the moment we are optimistic that stability will get better. 

Recent Avalanches? None

Observed Cracking? None

Experienced Collapsing? None

The snowpack is generally quite solid, except for the interface under the storm snow. Use caution on wind loaded slopes that could break at the
bottom of the storm snow layer or within the drifted snow slab. Steep slopes can still pose a problem considering the addition of extra weight coming during the next 24 hours.

Recent Avalanches? None

Observed Cracking? None

Experienced Collapsing? None

Experienced PWL at ground level is alive and well but seems to be healing with the thick insulation layer of snow covering it. Because the snowpack is generally very cohesive on top of the PWL it will be very hard to trigger. The biggest concern is of a couple of slabs of drifted snow in the top 1 to 2 feet of snow. Not sure how widespread the near surface facet layer is, but I found a very touchy layer at high elevation on an east facing slope. this is something to keep in mind after the next storm cycle adds weight and stress to this layer. My biggest concern is of the wind slabs mostly on NE slopes. I observed a lot of blowing snow today that will add weight and stress to these areas. Watch for cracking as you enter wind loaded slopes. It is going to be very difficult to trigger the deep persistent weak layer, what could happen is that a wind slab avalanche could step down into the deeper snowpack triggering a sleeping monster. We don't want to wake him up!

Snow pit location on the east slope of Sawtell. Elevation 7600 ft on north facing 18 degree slope. HS 155cm HN 5cm. Scored ECTN14@132cm and ECTN25@115cm FC confirmed on the ground underneath a MF crust. Although this PWL exists the crystals had some cohesion. About 4F.

Second pit was excavated at 9000ft SW of Sawtell Peak at the head of Yale Creek on an east facing 20 degree slope. HS 255cm HN 8cm. Scored ECTN1@247cm and ECTN17@200cm. I didn't dig down to the facet layer at the bottom of the snowpack, but could feel a strong MF crust at about 35cm off the ground and then very low resistance after poking through the crust into the facet layer. I did identify a surface facet layer at 8cm into the snowpack, just under the new snow, that was very touchy.

We rode from the Sawtell Road up to Mount Jefferson then through to upper Hell Roaring Creek on a tour of the range and accident sites with three members of the Fremont County SAR team, Randy, Nick and Justin. The ride was a beautiful traverse of the range. There was one very large natural avalanche that failed a week earlier on Mount Jefferson and several others that broke during the last loading event. We dug a couple of snowpits, finding a DEEP (200-230 cm HS) and mostly stable snowpack (ECTXs). Brett Rasmusen found a layer of NSF in the head of the White Elephant drainage and an avalanche nearby at Lionhead is indicative of a more widespread weak layer 1-2’ under the surface. LOW / MODERATE seemed appropriate on deeper instabilities, but with anticipated loading, we must communicate the concern about this new weak layer and the potential for large avalanches breaking in the upper part of the snowpack.

We rode into the Hell Roaring drainage via Willow Creek to Tin Cup Pass from the Keg Springs parking lot in Idaho. There was no recent avalanche activity observed along this route. I dug one pit at Tin Cup Pass on the Montana side at 8000' on a NW aspect. Total snow depth was 165cm and the snowpack was relatively homogenous with the exception of one melt freeze crust near the bottom of the snowpack at 39cm. From the melt freeze crust to the ground the structure was very sugary. A CT and an ECT were completed with results as follows, CT 12 @135cm, CT 28@ 115cm, and ECTN 16@ 150cm. My greatest concern in the snowpack was the melt freeze crust near the bottom of the snowpack.

Skiid the into the Hellroaring Drainage 12/29/21-1/2/22. Did not observe any natural slide activity or indicators of instability during the tour into the hut. Snow depth was consistently 130 cm at 8000'. Skiid W & NW aspects up to 35 degree slope angle. Fair structure + Good Strength = Generally Stable Conditions in the Eastern Centennial.

WNW aspect, 8,000' HS 130 cm
CT3 Q3 @ 20 cm (new snow)
CT20 Q2.5 @60 cm (new snow)
ECT-N+

We rode into Two Top Mtn. on the two top Loop Road from the Island Park side. Dug a pit on a road cut on a west aspect and there was 4 feet of snow, 3/4 of it from the recent storm. New snow was right side up and there was minimal old snow to create instability below the new snow at this elevation. Our second pit was at 7,800’, NE aspect, heavily wind loaded. Snow depth was 6 feet and the lower snowpack was very hard and stable. We dug a third pit on a SE aspect at 8,100’. Depth here was 4.5 feet. There was a crust above facets about 1.5 feet above the ground. This layer could be capable of producing avalanches. There was one natural avalanche that occurred during the storm on Lionhead Ridge. We did not see other signs of instability today. Remain cautious of the possibility of avalanches breaking 3 feet deep below the recent large storm.

I drove up the Sawtelle Peak road and dug a pit at the snow marker at 8,800'. There was 1.5 feet (60 cm) of snow on the ground. Around 7,000' the snow was on all aspects, but below that there were melted patches. The snow was supportable and there was no cracking or collapsing. A layer of weak, sugary snow 1 foot off the ground broke clean in ststabilityests (ECTP 18, 21) and I anticipate this layer will get weaker with time. On the surface there is a thin layer of snow that is faceting and getting weaker. Photos and snsnowpitre on this page.