Trip Planning for Bridgers

Photo: R. Lindsey

As we returned to Frazier Basin from below, we saw five natural avalanches on the southeast-facing wall of the basin. They entrained only the 1 to 2 inches of snow that had fallen during the day. However, they were notable in that they ran 500 to 700 vertical feet. They indicate that the new snow may not bond well to the old snow surface. A crust formed by the recent warm temperatures and sunny skies is the subsurface that snow is falling on. This will become a more significant concern as more snow falls this week. Photo: GNFAC
 

From obs: "Noticed this large avalanche in unsupported terrain yesterday morning. I called it HS-N-R3-D3-U although it looks to have failed on facets at the ground. Frequent flyer but impressive. Debris was approx. the size of a football field and 8-10' deep, ran full extent of D3 track." A Newman

From obs: "Noticed this large avalanche in unsupported terrain yesterday morning. I called it HS-N-R3-D3-U although it looks to have failed on facets at the ground. Frequent flyer but impressive. Debris was approx. the size of a football field and 8-10' deep, ran full extent of D3 track." A Newman

From obs: "Noticed this large avalanche in unsupported terrain yesterday morning. I called it HS-N-R3-D3-U although it looks to have failed on facets at the ground. Frequent flyer but impressive. Debris was approx. the size of a football field and 8-10' deep, ran full extent of D3 track." A Newman

From IG message 3/11/23: "...yesterday, at Fairy Lake, very windy and this slid naturally sometime between when we got to the area at noon and 3oclock. There was also a smaller natural wind slab in the northern bowl with arrowhead. Observed wind loading all day." Photo: P. Norvell

From IG, “Noticed a few natural and human triggered surface slides of the new snow on the old crust layer. All of these were north of Bridger Bowl on The Ramp” C Lambert

From IG, “Noticed a few natural and human triggered surface slides of the new snow on the old crust layer. All of these were north of Bridger Bowl on The Ramp”

From Obs, "Toured wolverine bowl and noticed a couple of large slides near the ridge on NE aspects. The most obvious was this one on the Hourglass that looks like it went in the last week. The trigger could have been part of the massive cornices breaking off." Photo: R. Leslie

Intentionally triggered new snow avalanche at Flathead Pass. Photo: T Miller

Intentionally triggered new snow avalanche at Flathead Pass. Photo: T Miller

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

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

Drove up to Bridger at noon and saw a large avalanche on along the road north of the fire station. It was 75’ wide, 1-1.5’ deep and 25’ vertical. HS-N-R4-D1.5/2. It was on an east facing slope, south of the long slope that has cornices. Photo: GNFAC

Drove up to Bridger at noon and saw a large avalanche on along the road north of the fire station... The slope with cornices hadn’t slid at this point. On the way home at 3:30 the larger slope with cornices had slid. It was very big, possibly R5. 1.5-2’ deep, 200’ wide, huge chunks of hard slab and cornice. Looks like new wind-loaded snow with some gouges into older snow. Photo: GNFAC

Drove up to Bridger at noon and saw a large avalanche on along the road north of the fire station... The slope with cornices hadn’t slid at this point. On the way home at 3:30 the larger slope with cornices had slid. It was very big, possibly R5. 1.5-2’ deep, 200’ wide, huge chunks of hard slab and cornice. Looks like new wind-loaded snow with some gouges into older snow. Photo: GNFAC

About 34 degree rollover, 14 inch crown. Photo: E. Volk

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

Karl Birkeland got an ECTP9 under a wind slab on the Throne. We could feel the hard slab and softer, weaker snow under it with our ski pole. Photo: GNFAC

We founds areas that were scoured to the dirt and adjacent areas loaded from the wind. The evidence of strong wind was everywhere. Photo: GNFAC

At the ridgetop of the Throne we found deep wind slabs that had cracked naturally; a sign of instability. Photo: GNFAC

One maybe two distinct seemingly natural large natural slab avalanches on small slope directly next to bridger canyon drive.  One on the lookers left was likely cornice triggered, but on the right it's unclear to me if it propagated or released naturally.

One maybe two distinct seemingly natural large natural slab avalanches on small slope directly next to bridger canyon drive.  One on the lookers left was likely cornice triggered, but on the right it's unclear to me if it propagated or released naturally.

Thanks to everyone who came out and supported the Friends of the GNFAC at this year's King and Queen of the Ridge at Bridger Bowl! Photo: GNFAC

This year's King of the Ridge, Casey Bloomer with a record-setting 34 hikes. Thanks to everyone who came out and supported the Friends of the GNFAC at this year's King and Queen of the Ridge at Bridger Bowl! Photo: GNFAC

Thanks to everyone who came out and supported the Friends of the GNFAC at this year's King and Queen of the Ridge at Bridger Bowl! Photo: GNFAC

Thanks to everyone who came out and supported the Friends of the GNFAC at this year's King and Queen of the Ridge at Bridger Bowl! Photo: GNFAC

Impressive avalanche cycle in the Bridgers to view as the skies clear.  Most slides seemed to have happened mid storm.  Here’s some photos of a large slide on the west side/behind north boundary.  Photo: B. Sienkowski

Impressive avalanche cycle in the Bridgers to view as the skies clear.  Most slides seemed to have happened mid storm.  Here’s some photos of a large slide on the west side/behind north boundary.  Photo: B. Sienkowski

Debris from large avalanche cycle on 1/28-1/29. Photo: BBSP

From IG message: "Another one today. Back of buck creek. Triggered 100 yards above where I crossed below it in the safe zone, after I went by. No burials."

From obs 1/28/23: "While snowmobiling up Little Bear we witnessed this natural avalanche. There was 2-3' of new snow." Photo: J. Otis

From obs 1/28/23: "There were numerous debris piles, point releases, and crowns on the north face of Elephant and the northeast face of Blackmore this morning.  Most of them appeared to have run during the storm (1/27) and had been covered by at least 6 inches of new snow." Photo. S. Regnerus

From IG:

Fairy lake today (1/27/23), remote trigger from top of the ridge

About 2-2.5ft deep about 75-100 ft wide

From Big Sky Ski Patrol 1/21/23: "skier triggered a surface wind slab in Wyoming Bowl that broke 8-12” deep. It propagated to an estimated 150’ wide- SS, R1/D1.5... The slide was small, no one was hurt, and the avalanche was reported (which we appreciate), with no further public involvement other than the trigger."

Another slide was seen from the highway in Argentina Bowl. This slide appears to be a shallow soft slab that ~50 ft wide and ran ~500 vertical ft.