Snow Observations List

Centennial Range
Centennials - Montana
Hellroaring Canyon

Yesterday, I skied into Hellroaring Canyon with a group of 6 backcountry skiers staying the night at Hellroaring Hut. While guiding the skiers to the hut, we saw large deposits of avalanche debris in the bottom of major slide paths on west and southwest facing aspects of Mt. Nemesis. It appeared that some of these avalanches were roughly size 1 - 2.5. Numerous creek bottoms and cut banks had also avalanched into Hellroaring Creek. Even some very low angle NW facing gully features had been ripped out. Looking across the valley into the Blair Lake area, I noted only one very small slide on a steep, rocky aspect. I did not have a chance to dig a snow pit, but I did observe numerous huge “whoompfs” while ski touring, and it was obvious that the faceted layer underneath last week’s 6 inches of new snow was failing regularly.

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Centennial Range
Centennials - Idaho
Centennial Mountains between Reas and Taylor peaks
Incident details include images

We rode this area all day. No one in the group had ever ridden this area, so it was an exploitation day. I dug a pit on a S facing 10* slope at 8564’.
HS 144 with 6 distinct layers, everything above 60cm was fairly consistent, the bottom 60 was JUNK, all large grain facets that were very soft, with little to no cohesion. I was surprised by the failure I got at 132cm, it failed very easily on the shovel shear, and with a CT11. I got an ECTN17 also at 132cm, nothing else. I did a PST just for the sake of killing time at had a 15/end at the 60cm interface. If there is a large enough trigger I have no doubt that the current slab is capable of propagating, and if it does the slide will likely be big. We did not see any avalanche activity while riding or driving in.

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Centennial Range
Centennials - Montana
Hell Roaring Creek
Incident details include images

Remote triggered several slides from bottom of slope on south facing slope.

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Centennial Range
Centennials - Montana
Hellroaring Drainage
Incident details include images

Shallow snowpack ~30", west facing terrain around 8200' is faceted except for the top 6 inches. We observed poor structure and fair to good strength due to a lack of distinct layering (its mostly facets top to bottom).

On an east facing slope at 8,300' we observed a slightly deeper snowpack, but still widespread faceting. Poor structure but good strength. During a pit test at this aspect we did not get propogation on any layers (on 1/5/19.) This was all before the most recent round of snowfall however, clearly the facets present a major persistent layer that will cause issues with increased loading.

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Centennial Range
Reas Peak
Snowmobile triggered avalanche near Reas Peak
Incident details include images

From e-mail:"a snowmobile triggered slide in a S aspect in the Blue Creek Drainage SE of Reas Peak in the Centennials.  No one was caught and no injuries "

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Centennial Range
Centennials - Montana
Hellroaring Drainage: Huge "Whumphs"
Incident details include images

I was in the Hellroaring Drainage Yesterday, snow depths below 7,000' hover around 18", around 8,000' snow depths increase significantly but are still shallow i.e. less than 30". Witnessed the largest "whoomphs" I have ever felt (that's saying something since last Decemeber/Jan was horrendous), interestingly much of this was felt returning on the same skin track, telling me this is a stubborn layer that may not give right away. The largest was a collapse in a meadow nearly 0.25 miles long.

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Centennial Range
Give us your observations!
Incident details include images

After last season's two snowmobiler avalanche fatalities on Reas Peak in the Centennial Range we created this web page so riders could get good, relevant information regarding snowpack and avalanches. Although the Centennial Range is not part of the Gallatin National Forest Avalanche Center's forecast area, we are the closest avalanche center and have valuable information to share.

  • The snowpack in the Lionhead area outside West Yellowstone is typically very similar to the Centennial Range. When we issue Avalanche Warnings in Lionhead, the Centennials are also dangerous. Pictures, photos, and observations from the Lionhead area are windows into the conditions in the Centennials.
  • We designed this web page to be a one-stop-shop for anyone riding or skiing in the Centennials.
  • We need your observations to keep everyone safe. Fill out a form and let us know what you found and attach pictures or videos.
  • If you are riding in other parts of southeastern Idaho, go to avalanche.org and find the nearest avalanche center to get updated information. The snowpack and avalanche concerns in regions adjacent to avalanche centers are typically similar:
  • Another great resource for avalanche information can be found at the Adam Anderson Avalanche Project on Facebook.
  • Avalanche Education is paramount to making good decisions. All avalanche education in Idaho is listed HERE.
  • If you would like to sponsor a 1-hour avalanche awareness class for your store, club, or organization, drop us a line. We may be able to accommodate that.

Do not hesitate to reach out if you have any questions or suggestions. This webpage is a work in progress. Email us at mtavalanche@gmail.com

We hope everyone has a safe season!

GNFAC Forecasters:

Doug Chabot
Alex Marienthal
Eric Knoff
Ian Hoyer

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