Regional Conditions for Centennial Range

From (5/17/20): "...WS - ASu - R3 - D2 - I SE face of Middle Basin Peak starting at 10,000' Estimated SZ of 30° Slab depth of about 8". We were out too late in the day and chose to ignore a number of observational warnings. We were lucky and remotely triggered the avalanche below us."

A very large natural wet slab ran on the afternoon of 5/19 at the Yellowstone Club. (Screenshot from the Y.C. Timberline chair webcam)

From obs: "Here are a few snaps from yesterday (5/2/20), looking into the Absaroka from up on Emigrant. Fair bit of smaller, pockety wet slab activity in steep, rocky terrain near the middle/upper transition. I didn't see anything larger than D2 or any activity in true upper elevation terrain." Photo: B. VandenBos

From obs: "Here are a few snaps from yesterday (5/2/20), looking into the Absaroka from up on Emigrant. Fair bit of smaller, pockety wet slab activity in steep, rocky terrain near the middle/upper transition. I didn't see anything larger than D2 or any activity in true upper elevation terrain." Photo: B. VandenBos

From obs (5/3/20): "N facing gulley, probably similar results from the Pine Creek avalanche posted on 4/29. Avalanche appears to be natural and possibly a couple days old. Ran about 400’ wide in the cone and damned up the creek with massive cement-like debris. There were more similar avalanches on N facing aspects the more I traveled. The skinning was isothermic and sloppy as each step fell through the snowpack to the ground"

From e-mail (5/1/20): "...the mountains are coming unglued with the 4 nights of no freeze and heavy rain.  My party ventured up pine creek to take a look and found this big one that ran either yesterday or last night. 

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From obs (4/26/20): "....a wet slide from a n-ne couloir up mission creek near elephant head in the absarokas between 10-11:30 this morning. Snow did not freeze over last night and was heavily saturated early this morning before the sun rose." Photo: @laura_delray

All surfaces except the upper North faces were getting wet and sticky. We observed lots of wet loose avalanches actively happening on SE-E facing slopes. We found some cold buffy snow on north-facing slopes, not amazing skiing. There was one small crown on a steep East facing slope that looked to be from the most recent storm but everything else was loose wet. Small wind slabs from the last snow seemed to be glued down today. Photo: S. Jonas

From IG obs (4/19/20): "Saw quite a few natural wet slides back in Middle Basin over the past two days, April 17-18. Witnessed several break loose naturally after about 2pm on anything from SW to SE slopes." Photo: @joshpelczar

Fresh drifts broke naturally along the ridgeline which became long running wet slides. 4/17/20. Photo: GNFAC

Pinwheels of snow indicate the surface is wet and losing strength. These were observed at Bridger on 4/17/20, caused by a skier crossing above. Photo: A. Crawford

Skiers in Beaver Creek in southern Madison Range on 4/12/20 reported: "...There were probably a couple dozen [wet slides] in total, including several small ones that ran into Beaver Creek road. Every solar aspect had multiple slides from the past few days of warm weather, at elevations from the road up to 10000', but none were larger than any my partner and I observed near Lionhead on 4/9 (≤D2)." Photo: S. Reinsel

From IG message (4/10/20): "Huge cornice release on north face of Blackmore today around 11am. North face was not hot yet but I am guessing the rocks on the back side transferred the heat?" Photo: @graeme.emerson

From obs (4/8/20): "My partner and I noticed this slide as we summited 10602 at approximately 10:30am, which is when I took the first photo and was able to capture the full runout. After our descent of the peak, we skinned back up to the slide to get a better look (the second photo). The slide appeared approximately a day old, with a crown 1-2 feet deep, on an almost directly north-facing aspect at 10200" elevation. It broke right along the rocks that had heated up in the sun, and was around 200-300 feet at its widest. We did not get close enough to determine which layer failed (suspected wind from the heavy wind-crust in the neighboring area), but the debris at the bottom indicated it was a wet slide." Photo: L. Ippolito

Cornice triggered avalanches in Mundy's Bowl at Bridger Bowl. Unsure if natural or skier triggered from the ridgeline. Observed the morning of 4/5/20. Appear to be dry slab/loose. Photo: T. Gittins

From obs. (4/4/20): "Rode Tepee today... Got ECTP 24 & 25 on a thin layer of SH... We also saw a few cornice drops that pulled out small slabs, new snow only..." Photo: E. Knoff

Close up of a crystal from the surface hoar layer buried 2-3 feet deep north of Bridger Bowl and throughout most of the advisory area.

From 4/3/20: "I dug a quick pit at ~7450’ on a protected east 36 degree slope - HS 240cm...ECTP18@175 on 3-6mm preserved surface hoar (photos -1mm grid)... All results repeated identically in a second ECT... Seeing the reactive SH layer I opted out of skiing anything that had a distinct rollover or was steeper..." Photo: Z. Miller

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

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

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

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

From obs form: "While approaching Black Mountain from Pine Creek Lake.... We skied South aspect and as it warmed we triggered D1 R1 slabs that ran slow and short." Photo: T. Hoefler

From email: "Photo attached of a natural avalanche from yesterday, just south of Cooke City.  It's on an E, NE aspect, with a crown around 9,300'.  Looks like it occurred yesterday am, as a result of a cornice fall." B. Fredlund

Skiers saw this 2-4' deep natural crown on Sunday 2/23/20. Photo: from IG @skishot

"Avalanche debris we encountered while skinning up the access road. It piled roughly 15-20 feet onto the road." Photo: T. Papritz

"Very large and destructive deep slab just north of emigrant peak on a east-facing aspect. The debris likely ran over 1000 vertical feet and stopped towards the bottom right of the image. We think the smaller slide on the far right was triggered as a secondary slide as a result." Photo: T. Papritz

"Very large and destructive deep slab just north of emigrant peak on a east-facing aspect. The debris likely ran over 1000 vertical feet and stopped towards the bottom right of the image. We think the smaller slide on the far right was triggered as a secondary slide as a result." Photo: T. Papritz

From IG #gnfacobs post: "An avalanche from early Tuesday (02/18) morning caused by a natural cornice fall. Note the step down partway down the path. ENE @ 9700. Ran 1300’." Photo: A. Whitmore