Snow Observations List

From IG 12/3: Hey guys, just getting back from Cooke. Confirming more of what you saw, lots of large natural avalanches up high. Most notable was this massive slide on fox, looks to have broke 2-6’ deep and over 1000’ wide. Couldn’t quite see the toe from our tour but it looked to have run over 1000’ vertical. Never have seen one so large on Fox… we stuck on sub 25° terrain which was hard to move in. Lots of whumphing but not much (if any) cracking...

We dug a pit on a W/WNW slope at around 9100 ft in the republic creek drainage. CT 18 and ECTN34 (ECTX then we hit it extra hard 4 more times) on the weak layer about 70 cm down. But overall snowpack was upright and it seemed to be settling down more than we thought. But then as we approached the ridge we triggered 5 separate large collapses ("Whumphs"), all on WSW/SW slopes (between 8700 and 9200 ft). Pole probes revealed a light crust about 12 inches down. 

From IG 12/3: It was natural. Happened last night or this morning. It hadn't slid when we left yesterday. We were first tracks in today, and there were no tracks above or below this slide. Crown at the peak was around 6'. Average 2-3' crown. 10' debris piles at least.

skied over by slush mans lift yesterday.

Got some settling on lower angle above base of lift.

We observed no natural avalanches or overt signs of instability, although one group in the parking lot mentioned seeing a small slide south in Sage Basin past the Otter Slide. The foot of new snow was wind affected. Human-triggered avalanches in the new snow and wind slabs were possible. These will stabilize in the next few days unless there is continued loading. 

We dug in Carrot Basin and on the slope up to the weather station. We did not find the weak layers of surface hoar or near-surface faceting like at Lionhead Ridge. I am not convinced it doesn’t exist anywhere, but it does not appear to be widespread. Test results were ECTN 11-15 under the foot of new snow. 

Lots of avalanche activity. Lots of cracking and propagation from the skis. 

Near Cooke City (12/2/22) we rode to the cabins at Lulu Pass, then to Round Lake, then to Daisy Pass. Visibility was 50/50, so we didn't see all terrain clearly. We saw multiple large natural avalanches that broke last night or early this morning. The largest were 3 on Scotch Bonnet (R2-D2), 1 on Henderson in the big east facing slide path (R1-D2) and 1 on Old Man Ray's on Republic Mtn (no photo). We also saw 4-5 smaller wind slabs (R1-D1). The larger avalanches we suspect broke on a layer of weak snow that formed last week and is now buried 2-3 feet deep, and deeper on high wind-loaded slopes. In a snowpit on West Henderson we had ECTP23 and ECTP24 about 2 feet deep on a layer of 1mm facets. Below that the snowpack seemed generally strong. Based on the recent natural avalanche activity, this is a weak layer we will have to keep an eye on going forward, and it could produce human-triggered avalanches for at least the next few days.

Today our party of three skied Blackmore peak, knowing beforehand the new snow and wind would keep us off the standard East Ridge to the summit, but still wanted to ski a lap on the lower section of that same ridge. Beforehand we were able to easily trigger shallow, short running windslabs by knocking down small cornices. We then headed up to the summit from the largely low angled SE sub-ridge and skied wind scour back to the trail. This lower angle terrain whumped on us a few times, whenever we stepped out of the trees, a hasty hand pit showed a thin sun crust under the new snow interface to be the culprit. Thought the attached picture may help some folks decided on weekend plans. Thanks!

We rode near Cooke City where more than 20" of snow has fallen since yesterday morning, and more snow is expected tonight. This new snow creates dangerous avalanche conditions and we expect natural and human-triggered avalanches over the next 24-72 hours. While touring on skis we experienced a couple large collapses. 

At our snowpit, HS was 55-60” (140-150cm), New snow was 21”=1.2”SWE, and we had ECTP19 and 23 above a melt-freeze crust that formed last week, buried 26-28” deep (6-8” below the newest snow). The snowpack below the crust was small rounded facets (0.5-1mm) and average 4F to 1F hard. Snowfall was 1-2cm/hr. Wind was gusting moderate to strong and seemed like it was hitting harder above us, at ridgelines and starting zones. 

ECT Results - ECTN 11 at 55cm

Location: Bacon Rind, Skillet, about the center of the upper skillet meadow, approx 100' below the ridge line N 44deg58.3210' W 111deg05.8191

Weather: Temp ~25F, cloudy, moderate snowfall, winds mild in trees, moderate winds on ridge line

Heading: E (110deg)

Elevation: 8890

Slope Angle: 34deg

Total Snow Depth: 110cm

We observed about 50-55cm of new and wind deposited snow on the eastern aspects that we assumed had been from snowfall/wind over the last week.  This new snow layer was generally F hardness.  The new snow was weakly supported by a 3cm thick faceted layer.  The ECTN 11 result was due to this faceted layer collapsing.  The remaining base snow pack was 50-55cm thick and approximately 2F hardness.  We repeated the test 2x in the same pit by digging back and retesting, the faceted layer failed both times without propagation, the ECTN 11 result was clear in the second test, the first test was hard to interpret but allowed us to identify the problem layer.  ECTX result on the remaining 55cm thick base snow layer. 

Wind loading produced dense snow drifts that were prevalent along the ridge line, but in the protected east aspect meadows below the ridge line there was much less evidence of denser wind loading.  We did not observe any whoomping either skinning up or skiing down or any signs of natural avalanches.   We skied the east facing short meadow just south of the skillet, then skied the SW facing meadow to the west of the ridge line and lastly skied the skillet to the valley floor.  As someone else reported earlier in the season the bottom half elevation of the run to the valley floor has many exposed downed trees and hidden hazards, personally I won't return to ski there until there is more snow depth at lower elevations.  The SW facing meadow had a supportable suncrust layer, with a mix of 6"-24" of wind drifted new snow depth, depending on where/how the wind had scoured it.

Pretty solid conditions yesterday. Some drifting occurring at the top but better then expected. Pit showed a right side up pack with the usual small layer of facets at ground level. ICT 25, slight but stable wind packed layer on top 2 in. Decent felt really good and conditions felt comfortable enough to ski any aspect on Ellis.

Good skiing on the backside of Lick today.

Dug a test pit on the backside out of curiosity and found 95cm of snow and a ECTN16 score @ 31cm down.

Dense slab that fractured on top of a 1F crust.

The snowpack turned out to be more stable than I had expected. 90cm at elevation with descent cohesion. 10cm of new snow. Compression test resulted in a CTN. Extended column test resulted in ECTX. I am still wary of some wind loaded drifts that could crack or collapse but didn't find any. There is a weak faceted layer about 20cm down that could become a problem with a new load of snow.

90cm at elevation with descent cohesion. 10cm of new snow. Compression test resulted in a CTN. Extended column test resulted in ECTX.

We sledded from Buttermilk to Ski Hill and dug a pit at 8000'. Snow depth was 80 cm, ECTN15 on E aspect–no NSFs or surface hoar at the pit.

While touring up Lionhead Ridge we triggered a whumpf with a noticeable crack on wind pillows at 8500’. At the whumpf snow depth was 83 cm on the NE aspect with ECTP11– failed on a layer of near surface facets.

As the terrain below the ridge (to the east) became steeper, we triggered a loud whumpf at 8600’. At the whumpf snow depth was 105 cm on NE aspect with 2x ECTP11. This was on a well-defined layer of 4mm surface hoar 35 cm from the surface. All ECTPs were on NE aspects with new snow and wind load atop the layer. This layer of near surface facets and surface hoar is our primary concern, and triggering a slide in steeper terrain with this weak layer seemed likely today. 

Saw natural avalanche debris below the cliffs on the NE face of Fan from the resort. Tons of wind loading the last few days. Light wasn't good to get a clear picture. Looked like a few different smaller avalanches but could have gone all at once. 

Skier triggered wind slab avalanche around 2pm, along the edge of north Bowl and Bronco near "The John". Crown 6-10" deep and 30 feet wide, hard slab of recent drifted snow. HS-ASc-D1.5. Strong wind blowing steady from the south-southwest and transporting snow, filling in tracks rapidly.

Immediately after this slide, I saw what I assume was skier triggered, slide of similar size a little further down the bowl with crown drifting in. Beacon check of debris produced no signal, barely deep enough to bury someone.

On a northeast facing slope at 9,100' near the ridge that divides middle and beehive basins my party dug a pit that was 65 centimeters deep, the extended column test had a score of ECTN 19 at 37cm. The layer at 37cm from ground appeared to be 5cm of sugary fist density snow sandwiched between layers of 4finger density snow.

We observed small shooting cracks up to 6 inches while traveling through freshly wind loaded snow near ridgelines. 

Triggered a small(d1r1?) wind slab off the bridger chair in bounds at bridger. Little skiers right of bumble chute on the roll over skiers left of bronco. NE face. Rollover around 35 degrees mellowing throughout the run. The face had tracks from earlier today before i triggered the slide. I was able to self arrest and stop myself before being carried. The crown was around 20-25 ft wide and the slide ran roughly 100ft downhill before stopping. Both myself and my partner skied away unharmed. Tons of people touring up bridger today, many without backpacks/ beacon shovel probe.