Regional Conditions for Bridgers

Observed this 8-12" slab on 3/30/20. Appears to have been triggered by cornice fall. Also observed several small wet loose slides from previous day and this morning. Photo: GNFAC

We dug this pit adjacent to a snowmobiler triggered avalanche. It broke on the surface hoar layer which is located at the top blue crystal card. The bottom card denotes the larger grains of facets that formed early in the winter. Photo: GNFAC

This surface hoar crystal is almost 1.5 cm (each square is 2mm) and was the weak layer in a few avalanches on Buck Ridge (3/29/20). Photo: GNFAC

There were many tracks in Buck Ridge and only a few small slides in First Yellowmule. This picture is looking SW towards Sphinx Mountain. Feathery crystals of surface hoar are buried 1-1.5' under the surface and are a concern. This layer seems to be more prevalent in protected areas. Photo: GNFAC

We saw this natural avalanche from afar. It was NE aspect and likely failed on a layer of surface hoar 1-1.5' deep. The Madison Valley is in the background. Photo: GNFAC

Sunday (3/29/20) skiers near Fairy Lake saw this cornice collapse that ran for quite a ways in October bowl. Photo: T. Gittins

From obs. (3/29/20): "Significant wind started building mid morning, forming even bigger cornices and wind loading many slopes. Noticed this slide on an East/Northeast aspect at the back of the bowl above Maid of the Mist creek, possibly triggered by cornice fall but unknown. Happened between 9:45am and 11:30am today, as at 9:30am it was not there, and when we returned to the spot around 11:30am the slide was visible." Photo: CP

Significant cornice growth and wind transport on Bridger Ridge. Photo: T. Allen

From obs: "We toured up in the Throne area today. Moderate winds were blowing snow at mid elevations and ridgetops. We found dry boot top powder on East facing slopes, the snow skied upside down. We observed loose and slab avalanches on many aspects up high and at mid elevations, all looked like new snow avalanches that happened yesterday. I’ve attached a photo of an east facing slope near the Throne."  Photo: S. Jonas

A skier triggered slide on a windloaded slope just north of Bridger Bowl. The skier lost their ski in the slide. Photo: R. Anderson

In the Bridger Range, avalanches released naturally on a density change in the new snow sometime Tuesday night (3/24). Photo: E. Knoff

In the Bridger Range, avalanches released naturally on a density change in the new snow sometime Tuesday night (3/24). Photo: E. Knoff

Snowfall throughout the afternoon fluctuated between S1 - S5 (during brief squalls). The winds started out moderate and from the west but calmed by the last lap ~5 pm. The new snow (from last night/this morning) was fairly well bonded to the sun/melt-freeze crust below, but the storm came in subtly upside down. Today’s snowfall (accumulating ~3” while skiing between 1-530) was light. Right along the ridgeline, we triggered 4 predictable small storm slabs 4~6” deep on the upside-down storm snow from last night/this morning, but surprisingly not on the old crust. They were each 5-10m wide x 5m long and only ran ~5m vertically. Photo: Z Miller

This is a photo of a small roof avalanche near Island Park. Warming temperatures cause water to percolate through the snow which lubricates the sliding surface. Roof avalanches have injured and killed people in the past, just one more thing to worry about. Photo: M.E. 

Dave Zinn digs a hand pit along the ridge to assess how the new snow is sticking to the ice crust. Photo: GNFAC

Obs: "School bus size cornices over Easterly portions of Lionhead Ridge. It is hard to tell from the photo, but the largest cornices were about 20-25' tall. We dug a few pits on East Facing slopes between 9,000-9,500 ft with the worst result being an ECTN-21 however these Cornices are primed and ready to fall with the abundant sunshine and warming weather." Photo: JR

From e-mail: "Natural wet slides... caused us to back off our plan of heading that way and ski a north, shady aspect instead. On a southern aspect. 9000ft. 1:30pm. We dug a hasty pit and observed a weak layer about 1m down. The facets were beginning to round." Photo: K. Master

From IG post with #gnfacobs: "I triggered a small windslab, mid slope on the north face of Wilson. It was a a pretty stubborn slab that broke above me. Cross loaded from lookers right. 6-8” deep." Photo: B Gill

From IG post with #gnfacobs: "I triggered a small windslab, mid slope on the north face of Wilson. It was a a pretty stubborn slab that broke above me. Cross loaded from lookers right. 6-8” deep." Photo: B Gill

From south of Big Sky yesterday 3/17 about 9:00, just north of Buck Ridge at 8500'. Large surface hoar on northerly aspects. Photo: Spence

We dug near the top of Bacon Rind and found 155cm of snow. Our primary concern is with the upper snowpack. As it warms and wets we can expect an increase of avalanche activity on the ice crusts. Facets are still dry and soft at the bottom of the pack and I got this layer to break with an ECTP29. Photo: GNFAC

We observed 7 wet, loose snow avalanches today in the Northern Bridger Range. All avalanches were in the R1, D1-1.5 size range. They would be consequential in the steep, technical terrain where they occurred. Photo: GNFAC

We observed 7 wet, loose snow avalanches today in the Northern Bridger Range. All avalanches were in the R1, D1-1.5 size range. They would be consequential in the steep, technical terrain where they occurred. Photo: GNFAC

We intentionally triggered a small wind slab and cornice before committing to a north-facing line in Frazier Basin. Photo: GNFAC

Spencer Jonas, GNFAC intern, in a snowpit in Beehive Basin. We found over 6 feet of snow and just dug our the top 4 feet to assess the stability. The new snow is bonding well and there were no signs of instability. Photo: GNFAC

From obs. on 3/10/2020: "Really touchy windslab formation throughout the day. 6-12 in slabs running on freeze crust." Photo: D. Wyckoff

Cornices have grown rapidly in the last few days. These will be susceptible to breaking and could trigger pillows of wind slabs under them. Photo: Bridger Bowl Ski Patrol

Strong wind stripped snow off many slopes above treeline. Photo: GNFAC

This naturally triggered avalanche likely happened Tuesday morning. Strong wind loaded slopes and made huge cornices. Photo: GNFAC

The winds blew the new new into wind slabs that avalanched naturally yesterday. This photo was taken at 9:30 a.m. on Tuesday (3/10) by Evan Schock.

A falling cornice triggered a large slide in the wet snow on an east facing slope up Hyalite. It was north of Mt. Blackmore and west of History Rock. Photo: R. Parsons

A google earth view of the cornice triggered location, 

Photo: R. Parsons

Point releases across highway from Bacon Rind. 3/6/2020.

Photo: GNFAC

Point releases across the highway from Bacon Rind. 3/6/2020

Photo: GNFAC

Wet slide in Buffalo Horn Creek. 3/6/2020.

Photo: A. Norlander

Overview of an avalanche triggered on 2/27/2020 at 8:30 p.m. by a groomer between Storm Castle and Swan Creeks in the northern Gallatin Range. The driver was ok, but the machine did a full barrel roll and was very badly damaged. Photo: GNFAC

An avalanche triggered on 2/27/2020 at 8:30 p.m. by a groomer between Storm Castle and Swan Creeks in the northern Gallatin Range. The driver was ok, but the machine did a full barrel roll and was very badly damaged. The debris piled 8' deep on the road, which creates a terrain trap. Photo: GNFAC

An avalanche was triggered on 2/27/2020 at 8:30 p.m. by a groomer between Storm Castle and Swan Creeks in the northern Gallatin Range. The driver was ok, but the machine did a full barrel roll and was very badly damaged. Photo: GNFAC

Looking up the path of an avalanche triggered on 2/27/2020 at 8:30 p.m. by a groomer between Storm Castle and Swan Creeks in the northern Gallatin Range. The driver was ok, but the machine did a full barrel roll and was very badly damaged. Photo: GNFAC

Looking down the path of an avalanche triggered on 2/27/2020 at 8:30 p.m. by a groomer between Storm Castle and Swan Creeks in the northern Gallatin Range. The driver was ok, but the machine did a full barrel roll and was very badly damaged. Photo: GNFAC