24-25

Middle/Beehive Basins Obs

Date

Thu, 01/09/2025 - 09:00

Activity

Skiing

OVC with 10k cloud ceiling in the morning (S-1) which cleared to BKN high clouds by 1pm. No signs of wind transport from the previous 24hrs (tree tops holding snow, little/no snow surface clues at the prayer flags and below).

We took a quick look at the upper ~1m of the snowpack: generally non-consolidated fist-hardness snow. Small, dry-loose slides were observed in Going Home Shoot and on the west facing wall of Middle Basin. We were able to move the top 5-10cm of snow in short, occasional sluffs but did not experience any other signs of instability. No other signs of avalanche activity could be spotted in the area. By 3pm, wind on the summit of Lone Peak was transporting lots of snow.

Region

Northern Madison

Location (from list)

Beehive Basin

Observer Name

E. Webb

Read more about Rimed Weather Station

The GNFAC weather station at the top of Sawtelle provides wind, temperature and relative humidity information for forecasting (when it's not covered in a foot of rime ice. Photo: GNFAC

Island Park, 2025-01-09

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Read more about View from Sawtelle

Photo: GNFAC

Island Park, 2025-01-09

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Read more about Over Looking the Centennial Range

From the top of Sawtelle. Photo: GNFAC

Island Park, 2025-01-09

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Getting Better in the Centennials

Date

Thu, 01/09/2025 - 14:35

Activity

Snowmobiling

We spent the last two days in the Centennials. On Wednesday, we rode up to the vehicle shop, into Yale drainage, over to Hellroaring, and across the backside to the East Hotel Creek overlook. On Thursday, we went to our weather stations for repairs and visualized much of the range from the top of Sawtelle.

Day one focused on snowpack analysis as it was lightly snowing for most of the day S- -1 with 2-3" of accumulation throughout the day, and we did not have much for long-distance visibility. We triggered two collapses in a creek bed when someone (I) was stuck while riding toward East Hotel. We were able to see the smaller avalanche paths along Yale and the only slide was a R1, D1 cornice collapse. We dug on a north-facing slope at the pass over to Hellroaring Creek. The facet layer of concern is now buried a meter deep (4F+ hardness) with an ECTX on this layer. Total HS of 155 cm. We got ECTNs 14-29 on the three rain crust layers formed during the last storm cycle.

The south-facing pit overlooking East Hotel was a bit shallower, 125 cm HS. ECTP30 on a crust facet combo mid-snowpack and an extra-curricular ECTP31 on the facets that we have been primarily discussing this season.

On day two, we got up high, overlooked many avalanche paths, and saw only the slide that Randy Gravett (Rescue Randy) had previously reported in Mt. Jefferson Bowl.

The collapse and the snowpack structure indicate the potential of triggering an avalanche, but the likelihood has gone down. Given the depth of the weak layers, I am not confident that the snowpack assessment will provide full and accurate information. If folks are starting to push into avalanche terrain, my emphasis is to stick to paths that are less likely to avalanche (sheltered from the wind and less steep) and paths that have lower consequences (smaller slopes with clean runouts). As always, safe travel practices.

If people don't want to mess with the uncertainty of avalanche terrain right now, conditions are fantastic on many slopes less than 30 degrees.

Region

Island Park

Location (from list)

CENTENNIAL RANGE

Observer Name

Dave Zinn

Still Touchy, Cooke City - 9 Jan 2025

Read more about Still Touchy, Cooke City - 9 Jan 2025

New avalanches and old avalanches

Date

Thu, 01/09/2025 - 14:10

Activity

Snowmobiling

Ian and I rode north of Cooke City, had good visibility, and saw terrain from Daisy Pass to Mt. Abundance back to Lulu Pass, around the south side of Scotch Bonnet, then back around the north side of Sheep Mtn. to Round Lake.

We saw many avalanches of various types and ages. Some occurred today and within the last 24 hours and some were up to a week old. Avalanche types ranged from 3-6' deep and broke on weak layers near the bottom of the snowpack to shallow soft, fresh wind slabs, and we saw one 3-4' deep slide that looked like it broke within recent new and wind-drifted snow (photo attached, north end of Henderson).

The most notable avalanches were 2-3 slides that happened today:

1) When we rode away from our snowpit on Mt. Abundance we saw a fresh 3'deep x 10' wide slide that we might have remote triggered from the flat ridge above (photo attached). 2) About 45 minutes later, from a couple miles away, we saw a 4-6' deep avalanche that happened since we had been there, about 1000' up the ridge from our snowpit (photo). This slide was either natural or remote triggered by riders about 1000' away who were there after we were. 3) An avalanche on the south end of Henderson Bench that looked fresh and someone else thought happened today. This one was 6' deep and broke at the bottom of the snowpack.

There was also a very large avalanche on the north side of Fisher Mtn. that happened at some time in the last week (could have been 48 hours to a week old), regardless of timing, this slide further shows the deeper weak layers are a real problem as snowfall continues to adds weight to the snowpack.

Our snowpit produced an ECTX and had 4' of snow above a layer of surface hoar buried one foot off the ground with facets below.

Region

Cooke City

Location (from list)

Mount Abundance

Observer Name

Alex Marienthal

Skier Triggered Wind Slab Northern Bridgers

Date

Wed, 01/08/2025 - 12:45

Activity

Snowboarding

Wind slab around 3-12" deep. NE aspect at 8,000 feet. Occurred sometime on January 8th.

Region

Bridger Range

Cross loading in low elevation gullies in hyalite

Date

Thu, 01/09/2025 - 04:00

Activity

Ice Climbing

Went climbing in the greater G1 area yesterday. Pockety slide paths and gullies near G2- Hangover were starting to cross load. Slab formation was just beginning (surface cracking and notable propagation.) Slabs did not have the volume to be consequential, yet. There is a lot of AST (thigh deep trail breaking places). These lower elevation paths are often relatively benign since they are generally well protected. A little bit more wind and slab formation could create hazardous travel in this areas with unforgiving runouts.

Debris piles from recent DL and likely SS avalanches were observed under cliff bands and gully features in the area that have likely run naturally throughout this storm cycle.

Region

Northern Gallatin

Location (from list)

Hyalite - main fork

GNFAC Avalanche Forecast for Thu Jan 9, 2025

Snowpack and Avalanche Discussion

Wind slab avalanches are a concern near ridgetops from wind loading yesterday (loading this morning in Cooke), but they will be difficult to identify because they are covered by fresh snow. Use your judgment to determine where winds have deposited snow (cornices are a good clue) and avoid those places.

Persistent slab avalanches 2-4 deep may still happen. The likelihood is dropping and the weak layer of facets is getting stronger on many slopes BUT NOT ALL. Lionhead has lots of weak snow. A <a href="https://www.mtavalanche.com/node/33427"><… guide near Cooke City</a> yesterday found pretty strong snow in two snowpits, but then got a collapse in an area with thinner snow (~2.5’ deep). In the southern Madison Range, I experienced widespread collapsing <a href="https://www.mtavalanche.com/node/33297"><… days ago in Cabin Creek</a>, then Ian was <a href="https://www.mtavalanche.com/node/33406"><… in the Taylor Fork</a> 2 days ago and didn’t experience any collapsing. He did see a few recent avalanches and got some poor results in snowpack tests, so he was worried about being <a href="https://www.youtube.com/watch?v=WTLHcU4H8cY">lulled into a false sense of confidence</a>.

The challenge is that we can get clear warning signs of instability, but the snowpack never gives us clear signs of stability and there is always a lot of uncertainty. The snowpack may be moving in the right direction, but keep a healthy dose of skepticism. Read more in this <a href="https://www.mtavalanche.com/blog/snowpack-tug-war"><s… post</a> I wrote last week.

Today safe travel requires conservative decision making and cautious route finding, and today the avalanche danger is CONSIDERABLE. Avoid areas loaded by yesterday’s winds. If you choose to enter the peripheries of avalanche terrain, take baby steps and consider the consequences of a slide if your assessment is wrong.

Yesterday natural avalanches were spotted rumbling down steep terrain <a href="https://www.mtavalanche.com/node/33423">just north of Bridger Bowl</a> during a short period of rapid snowfall and wind loading. Early yesterday morning, the Bridger Bowl Ski Patrol triggered wind slabs just under the ridge 4-12 inches deep, then had to shut down the ridge midday due to snowfall and wind.

The good news is that winds weren’t hurricane force, and shifting directions prevented them from doing too much damage. The challenge today is that wind slabs will be hard to identify with fresh powder on top of them. Use your judgment to determine where winds deposited snow yesterday (cornices are a good clue) and avoid those places.

You’ll likely trigger a wind slab in areas loaded by yesterday’s winds. There’s also a chance that a slide in one of these places could break deeper on old facets. Today the avalanche danger is CONSIDERABLE on wind loaded slopes, and MODERATE on slopes not loaded by yesterday’s winds.

Very similar snowpack conditions exist in the Centennial Range near Island Park. Watch for wind slabs near ridge tops from winds that transported some snow yesterday. Persistent slab avalanches are still a major concern. The likelihood of triggering one has dropped but it’s not the same on all slopes. More likely places to trigger persistent slab avalanches are slopes with a thinner snowpack where you’re also more likely to hit a rock and smoke an A-arm on your sled.

Dave and Shannon (our education coordinator) rode with a few top notch guides and educators near the top of Yale Creek yesterday. They found signs of improving stability but also found signs of instability. He describes the situation well <a href="https://youtu.be/5jyQDWE32GI?feature=shared">… this video</a>, watch it. Read more in this <a href="https://www.mtavalanche.com/blog/snowpack-tug-war"><s… post</a> I wrote last week.

For today with lingering weakness in the snowpack, the avalanche danger is MODERATE. Heads up - this danger rating spans a wide range of conditions, don’t let your guard down.

Read more about GNFAC Avalanche Forecast for Thu Jan 9, 2025

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