Snow Observations List

Riders in Taylor Fork saw natural avalanches on Saturday, 12/9

Starting around 7500’ on E,S,W aspects we found extensive cracking and wumphing on faceting at the ground layer. Felt wumphs every few steps and had around 30 foot shooting cracks in meadows and on ridgelines. Total snow depth was never more than 45cm 

Got ECTP10/11 in a pit on an east facing slope at 9100'. The snowpack is about 60cm deep, with 30cm of facets and 30cm of fist to 4 finger hardness new snow . The test failed at the interface of the old facets and new snow. 

We decided to keep the skiing to below 30 degrees. After skiing one slope and skinning back up, we noticed widespread cracking around our ski tracks (image), but luckily the terrain was mellow enough that nothing moved. 

From IG on 12/10: "2 slides we triggered remotely in tepee yesterday"

We (a group of 4) skinned up Lionhead Ridge from the ID/MT border and found troubling conditions. Several small whoomphs were observed in the shallower, bushy snow at lower elevations, and we had a massive (~100-foot propagation) whoomph on the ridge proper where the cornice met the ridge. Accompanying those whoomphs, we observed shooting cracks at multiple low-angle locations. We performed 3 separate pits, the shallowest of which was 48cm @8113' and had an ECTP10. The next two pits were 65cm deep and the SnowPilots are attached. Every single pit had sizeable (~3mm) basal faceting and a pencil-hard ice layer sandwiched with more facets above in the lower snowpack. While cutting a PST, the entire column propagated (Q1) above the ice layer at 25cm from the ground. Be careful out there, the snowpack is super touchy. 

From text message: "The attached picture is a little slide that went off when I was doing small turns on an adjacent slope. That's Beaver Slide! There was more small slides south in the trees. Heard whumphing here and there."

Was splitboarding up near lions head ridge today. Made some bad decisions and kicked off a good slide in a NE facing chute. Was with 2 buddies, 1 of which skied the line 3 weeks ago.  Underneath about a foot of new powder snow there was a firm crust that seemed like it was old  hard windslab in the gut of the chute, and I think a sun crust on the riders left side(East aspect). We had 2 spots where we were planning to re group at, first was a small cubby area right before a slight rollover about 75 ft from the top. I dropped first, made some turns down toward the pulloff, as I pulled in, I triggered a good size slab that propagated maybe 40-50 ft across, at the rollover as I carved into the pulloff.  Pulled  all snow  out of the chute down to the ground. Seemed to have failed on sugary facets on ground/ice crust close to the ground... 

Went into the Lightning/Taylor Creek area of the Southern Madison’s in search of some powder skiing with the new snow. On our ascent toward Woodward Mountain via the backside, we found fresh snow varying from 2 inches at the trailhead to foot deep lightly drifted areas in the upper elevations. In the protected low angle gully we ascended this new snow sat atop either rocks or a very stout wind crust. The latter of which made for great skiing. We descended Woodward top down and assessed the possibility of thin (3”) wind slabs being reactive on the stout wind crust as the Woodward side seemed to have received a lot more loading from the storm’s E winds. As we rolled over to slightly steeper terrain, I noticed the snow stiffening just below my skis and gave it a few hops where I intentionally popped the pictured slab. With this information, we decided to carefully traverse to more protected trees and descend via a less wind loaded and hazardous route. We ski cut from tree to tree triggering a few more of these very small slabs before finding wonderful powder skiing lower on the mountain where the wind had significantly less effect. 
 

All of the slabs were 1 to 4 inches deep and propagated 5 to 15 feet wide. None of them possessed the mass or were on steep enough terrain to overcome and slide over the stauch wall. Overall was a great lesson in mitigating hazard and we were rewarded with some great turns. 

Went for a ski tour in the Southern Madison's up Lightning Creek in search of a deeper snowpack. Our tour brought us up Woodward Mountain via the E sub-ridge with a plan to ski in the bowl to the north on a NE aspect. The snowpack varied immensely due to sun effect/wind loading but overall found 50-60 cm of snow in the deeper locations. We performed 3 CTs in representative locations of our intended ski line and had results of CT21 Q2, CT15 Q2, and CTN. The columns broke on a layer of 4F facets midway down from the surface. Combining this data with a lack of other signs of instability (cracking, whumpfing, recent avalanches, recent loading), we decided to ski our intended line. 

Snow quality on the ascent and decent varied from "ripple pow" to breakable wind crust to unbreakable wind crust. Overall, was a great day in the BC getting familiar with our early season snowpack even though good ski conditions lacked. 

Observed evidence of natural slide activity yesterday while snowmobiling Buck Ridge. First pics are on a northerly aspect off Sphinx near the wilderness boundary, second set of pics are south facing off Pioneer Mtn.

Approx coordinates of slide #1: 45.15872, -111.46923

Approx coordinates of slide #2: 45.22781, -111.46531

We rode through Carrot and Sage Basin and up to the weather station above Sunlight Basin. We dug a pit on a SE facing aspect to see if the snowpack was transitioning from dry to wet. At 9,200' the air temperature was 18 F and the snowpack was dry throughout. Despite the cool temperature the snow surface was close to becoming wet (31 F). This was a good reminder that the sun angle has a significant impact on the snow surface this time of the year, which causes rapidly changing conditions. Additionally, we had an ECTP 13 on a layer of near surface facets 1.5' below the surface sitting on top of a melt freeze crust. This weak layer and the one near the bottom of the snowpack remain a concern.

Overall seemed like a deep HS (220 cm) versus other years I’ve seen here. High strength in pit (ECTP26), failure on facets below melt-freeze crust down 60 cm, and with no more obvious signs of instability. Felt weak snow deeper, but only dug in the top meter. North winds increasing throughout the day and any wind affected snow was shallow in depth. South aspects were crusted but protected N-facing or tree skiing was still great.

We rode to the Taylor Fork Weather station, then to the Wilderness Boundary above Beaver Creek, and then through Sage and Carrot Basin. There was 13-14" of new snow throughout the area. At the Wilderness Boundary we saw several R2-D2 avalanches on a NE facing ridgeline above Beaver Creek. We dug a pit on a SW aspect at 8,800' that was 9' in depth (HS: 279 cm). We had an ECTP 11 at the interface between the new and old snow. We also had an ECTP 24 on a layer of 1.0 mm facets sandwiched between two melt freeze crusts. These results and the recent avalanche activity highlighted the instability that exists from this most recent snow. When we were leaving our pit site the visibility improved, and we saw  a R3-D3 avalanche in a high alpine bowl. This avalanche confirmed that deep slab avalanches are still a concern for our advisory area.

We rode into the Taylor Fork area on a beautiful, sunny day. We saw three large avalanches that likely broke approximately one week ago in Sunlight Basin, Sage Basin, and at the head of Sage Creek. Sage Basin and Sunlight Basin were cornice-triggered hard slabs that broke 2-4 feet deep on wind-loaded slopes. The avalanche in Sage Basin broke several mature trees.

The slope that avalanched at the head of Sage Creek was a heavily wind-loaded 35-40 degree slope. It failed without a cornice trigger (as no overhanging cornices were above). We investigated this slide in greater depth. It failed on a layer of faceted snow 2-4' deep. In our stability test, we got an ECTP22 on the failure layer. Riders and skiers are less likely to trigger these large avalanches after four days without snow, but we don't trust these slopes. Every time it snows a little bit, we see large avalanches. They remain possible to trigger now. Choosing conservative terrain is the best management strategy - simple slopes with minimal wind-loading and fewer consequences or slopes less than 30 degrees in steepness. With more snow in the forecast, the danger will likely rise again this week. 

We rode into Tepee Basin. There was 1-2 feet of new snow with a few inches falling during the day. In a brief period of clearer skies we saw two natural avalanches on the steep slopes above the basin. Neither was huge, R2-D2. One ran about 500', both looked to be 1-3' deep. We saw another natural avalanche near Bacon Rind into the Gallatin River. 

The avalanche warning was certainly justified. We did not go near any steep terrain. Dug one pit and measured 1.8" SWE in the storm snow. ECTP 20 about 2 feet deep and an ECTP23 failed on the basal facets. We would plan to avoid steep slopes and runout zones for a while waiting for things to stabilize. 

Rode out Buck Ridge through 2nd & 3rd Yellowmules, McAtee Basin, and then out to Cedar Mtn. Saw no avalanches or signs of instability (no cracking, no collapsing). There were a few inches of new snow (2-4") that had been blown around by very strong winds. Fresh wind drifts had formed overnight on the trail and in spots our tracks were blown in by the time we were headed back out. The chief avalanche concern today was avalanches breaking in wind drifts. The possibility of triggering a slab breaking deep in the snowpack was a secondary concern. 

With snow and wind on the way tonight and through tomorrow, avalanches in the new snow and deep in the snowpack will both be more likely tomorrow. Expect an elevated danger. The details will depend on the amount of snow and wind, so make sure to check the forecast in the morning. 

I went on a little loop up and around Red Mountain today, and have a couple slides to report. Most notable was one that spanned about 2000’ of the north side of Red Mountain. It seemed to be 1-3’ deep in the newer snow, for the most part, but a portion of it broke 15’+ deep and ran at the ground. Judging by how little snow was on the debris, I’d guess it ran sometime Friday night or Saturday. This bowl frequently produces large avalanches, but this one was a real peach. 
I also saw another (much) smaller 1-2’ deep slide on the west-facing road cut just north of the Bacon Rind pullout. 

Via IG: “Large natural avalanche on the east side of redstreak peak down near West Yellowstone. 

And then another natural one right on the shoulder of white peak on the boundary.”

Big (tennis court size) collapse and whumpf on the upper meadows at Telemark Meadows in flat terrain. No other reactivity to report from a few laps on the main ski slope.