Trip Planning for Northern Gallatin

From email: “These pics are from last June 10-11, after the pass reopened on Friday. I was skiing the Gardner headwall at 5:30, solo, when this monster released. Yah. The initial cornice collapse triggered and entrained a secondary slab of varying thickness whose crown is seen in one of the photos.”

From obs 5/7/23: "Natural R3-4, D4 ripped out a large chunk of the south face of Wilson during the last warm period I would assume. Debris everywhere and one large boat-sized pile even scoured a path further down than the rest of the debris. Looked to be a mix of wet loose and wet slab release from high up. Alpha angle at the bottom of the debris was 25 degrees" Photo: C. Ellingson

Give Big Gallatin Valley is May 4-5. The Friends of the Avalanche Center are participating again this year and thank you for your support. Between 6pm on May 4 through 6pm on May 5 you can support your favorite local non-profits. Donate Here.

From Big Sky Ski Patrol: "Temps remained a little cooler than yesterday and generally topped out in the mid 40’s F. That didn’t stop the free water from moving
and continuing to destabilize the snowpack, primarily on solar aspects below 10,000’. Near full depth to full depth wet loose avalanches continued to naturally release in what was left of the A-Z’s as well as LRT which had not seen any activity yesterday." Photo: BSSP

From obs 4/7/23: "Small wind slab triggered by snowmobile. Slope was assessed by group as wind blown before climb.  No one was caught. East facing slope, Storm castle Ridge. Photo one shows trigger point where the Snowmobiler carved hard and set off the slab deeper in the snowpack"

From obs 4/7/23: "Small wind slab triggered by snowmobile. Slope was assessed by group as wind blown before climb.  No one was caught. East facing slope, Storm castle Ridge. Photo one shows trigger point where the Snowmobiler carved hard and set off the slab deeper in the snowpack."

From obs 4/7/23: "Small wind slab triggered by snowmobile. Slope was assessed by group as wind blown before climb.  No one was caught. East facing slope, Storm castle Ridge. Photo one shows trigger point where the Snowmobiler carved hard and set off the slab deeper in the snowpack"
 

We were snowmobiling up portal creek today near the hidden lakes trailhead and I set off a small slide remotely by riding below a small ridge. The slide was about 3 feet at its crown 30 or 40 feet wide and ran about 40 yards. It just came down to where my track had crossed underneath. Everything was fine and we stayed safe and continued on with our plan and had a nice day.

We were snowmobiling up portal creek today near the hidden lakes trailhead and I set off a small slide remotely by riding below a small ridge. The slide was about 3 feet at its crown 30 or 40 feet wide and ran about 40 yards. It just came down to where my track had crossed underneath. Everything was fine and we stayed safe and continued on with our plan and had a nice day.

We were snowmobiling up portal creek today near the hidden lakes trailhead and I set off a small slide remotely by riding below a small ridge. The slide was about 3 feet at its crown 30 or 40 feet wide and ran about 40 yards. It just came down to where my track had crossed underneath. Everything was fine and we stayed safe and continued on with our plan and had a nice day. 

From obs 3/26/23: "Saw a couple small natural slides breaking in the new snow. The one on the small slope beside the road actually appeared to have broken when a snow bike crossed the top just off the side of the road." Photo: J. Weingarten

From obs 3/26/23: "Saw a couple small natural slides breaking in the new snow.... occurred in the afternoon sometime" Photo: J. Weingarten

[On 3/25/23]: Skier reported, "Came across debris of a recent skier-triggered slide near the top of Little Ellis in a small, protected, eastern facing gully around 7,500'. Crown was ~3.5-1.5' deep, ~35' wide and it ran ~150'. Ski tracks were observed near the top of the crown and next to a small hole near the surface ~70' from the crown where it looks like someone self extracted. No signal was found with a beacon search and my group felt that the one track from the hole must have been from the same skier as the track near the crown." Photo: R. Beck

[On 3/25/23]: Skier reported, "Came across debris of a recent skier-triggered slide near the top of Little Ellis in a small, protected, eastern facing gully around 7,500'. Crown was ~3.5-1.5' deep, ~35' wide and it ran ~150'. Ski tracks were observed near the top of the crown and next to a small hole near the surface ~70' from the crown where it looks like someone self extracted. No signal was found with a beacon search and my group felt that the one track from the hole must have been from the same skier as the track near the crown." Photo: R. Beck

Photo: R. Lindsey

On 3/23/23 skiers in Hyalite saw this older avalanche on Alex Lowe peak. Photo: W. Casper

Photo of deep slab avalanche on Elephant Mtn from above. Photo: W. Casper  3/23/23

Saw this very large avalanche in NE face of Elephant this morning (3/23/23). Skiers left flank appears at a distance to be 8-10'. Photo: C. Babineau-Z

Large avalanche on Mt. Bole seen by skiers on 3/17/23.

We skied the ridge north of Blackmore (Tomahawk Ridge?) traveling between 6800' -9200' on SE-NE aspects.

On the ridge above, ~9400' on a NE aspect there was a natural avalanche, maybe cornice failure, probably same timeframe as the Divide slides. ran ~600'.

HS-N-D2-R2-O

Photo: R. Griffiths

I went for a walk up to divide basin today and noticed two slides that occurred on high, steep, north facing slopes last night (Tuesday night) when the wind picked up 

While investigating an avalanche that failed on a weak layer of facets buried in January, we notice a new layer that we will be looking for and testing as we move forward. Photo: GNFAC

Investigating a recent avalanche on Hyalite Peak. Photo: GNFAC

On Buck Ridge today (3/5/23) we found fresh, unstable drifts. This fresh slab was 4-6" deep. Cracking like this is a sign that wind slabs will avalanche on steeper slopes. Photo: GNFAC

Skier triggered avalanche on Elephant Mtn. 3/4/23. SS-ASu-R2-D1.5-I

Vertical Fall: ~700' Distance Traveled: ~1000' Aspect: 15 N Elevation of start zone: 9645'

Skier triggered avalanche on Elephant Mtn. 3/4/23. SS-ASu-R2-D1.5-I

Vertical Fall: ~700' Distance Traveled: ~1000' Aspect: 15 N Elevation of start zone: 9645'

Skier triggered avalanche on Elephant Mtn. 3/4/23. SS-ASu-R2-D1.5-I

Vertical Fall: ~700' Distance Traveled: ~1000' Aspect: 15 N Elevation of start zone: 9645'

Skier triggered deep slab avalanche on NE face of Hyalite Peak 3/4/23.

Skier triggered deep slab avalanche on NE face of Hyalite Peak 3/4/23.

Skier triggered deep slab avalanche on NE face of Hyalite Peak 3/4/23.

"Chunk of cornice fell off the top of Arden Peak. Notably the same aspect/elevation as the 2/27 observed natural slide on E face of Mt Bole but the cornice fall did not step down beyond the surface snow." Photo: M. Zia

From IG. “I spotted a large crown this morning on the E face of Bole. The crown appeared to be pretty deep, at least a few feet, and propagated quite wide. It also looked like there was a debris path coming down the apron of the E face of Hyalite peak, but I was too far away to know for sure.” N. Sramek

From IG: Skiers near Mt. Blackmore on 2/24 saw a large avalanche on the east side of Mt. Blackmore that appeared to have happened in the last 24 hours.

From email 2/24/23: "Came across this very large cornice that appeared to have broken naturally sometime in the past 24 hours. Saw a few others that had broken recently throughout our tour, but none as large as this." E. Heiman

Low winds/no snow transport when I was up there and the east face had little to no wind effect, probably 16-18in new snow. Saw this slide with about a 8-12in crown and 100ft wide on the north face, didn’t see any other activity aside from some small point releases on really steep east aspects.

From another party: Saw a sizable avalanche on the north east face of Blackmore, likely broke mid storm and was partly filled in already - estimated 20" deep, 100' wide. Had shooting cracks and collapsing while ascending northeast ridge. Hand pits showed planar results on an 8" harder slab beneath all the blower on top. 

We observed a few small crowns on steeper road cuts in Sourdough today, NW and W aspects. 4-8" at crown, 20-40' wide, ~10' vertical. They looked like storm slabs that had run overnight, maybe on a density change in the storm snow. Debris piles were small and covered with 2-3" of new snow. Low consequence, but maybe enough to surprise a kid or a dog. Photos were taken shortly above the 2 mile marker.

Was about 80% of the way up to the top of the middle meadow on history rock this morning when we remotely triggered a small avalanche from the skin track.  Slide was just new snow that had fallen within prior 24hrs.  Crown of about 8 inches, 20ish feet wide by 20 feet long.  Face that slid was east facing.  We took this as a sign to reconsider skiing something even as low key as history rock and decided to ski the skin track back.

[Dropped the pin for this observation exactly where I believe the observation to have occurred.  Took an OnX waypoint while out there to help too.]

Went for a ski up the Flanders drainage in Hyalite today. The day was punctuated by light winds and heavy snowfall.

On the skin in, we noted numerous D1 storm slab avalanches about 15cm down in the new snow on many aspects and elevations. Approaching a ridgeline, we experienced a shooting crack that propagated a very small slide in slightly wind affected snow. We dug an ECT on a SE facing aspect at 9000ft. We were unable to get propagation. Snow totals appeared to be higher than forecasted, with 60cm of new snow as of about 12:30. By the time we ripped skins, the area had received an additional 10cm of snow, putting totals around 60-70cm of low density snow on top of a stout melt freeze crust on the aspect we were skiing.
 

we did not observe any cracking collapsing or wumphing in buried weak layers, nor signs of avalanches on those layers. The new snow had very low SWE.

I sunk to the ground on Mt Ellis when I stepped out of my skis. A poor, unsupportable structure is not everywhere, but it certainly was on the ridge. Photo: GNFAC

"Found widespread surface hoar up storm castle creek on all sheltered slopes above 7500’." Photo: JR Mooney