Snow Observations List

This afternoon we went for a tour up Mt Ellis. The winds ripped across the ridge from the west, heavily loading the east to northeast aspects and building up some impressive cornices. We avoided the wind-loaded slopes and dug a pit in a protected meadow on a northeast aspect below the ridge. There was little evidence of wind loading and we observed strong stability in our pit. 

Our group toured around beehive, middle and bear basin. The wind has made the cornices huge at ridge lines and created obvious pillows and drifts and added texture to the snow surface and made the new snow noticeably denser than yesterday. The newest 15-20cm fell upside down. In our pit we noticed the top 20cm of new snow was F+ consisting of primarily large graupel, below that, the 20cm of new snow from yesterday was F- with snow trending from 4F to 1F over the next meter below. We had ECTN4 where this denser new snow from today overlayed yesterdays lower density snow. The NSF layer was about a meter from the surface and unreactive in our tests. Today was almost unskiably deep, and the nature of the new snow structure made burying a tip and pearling an expectation. 

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. 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.

From Olson creek I had a cloud free flat light view of the ridge from Saddle to Bridger Peak and looked with binoculars. There was a wind slab just north of quarter saddle that did not go over the cliffs. Probably 1-2’ deep, 30’ wide of new snow. There was a large wind slab on the north half of Between the Peaks (250’ wide) and one similar depth wind slab in the Pinnacles (100’ wide). Both of these broke 1-3’ deep immediately below the cornice and did not entrain much snow or propagate very wide or downslope given how much new snow there was. I could see the debris from the slide between the peaks which ran over 1000’ vertical to the top of the runout zone but relatively low volume.

Biggest of the cronies not pictured but around 3-5 m in height at the biggest on the west side of the ridge

From email, "At 12:45 p.m. I saw Climax run naturally. SS-N-R2-D2-I. The low visibility and distance made it hard to tell how deep the crown was, but based on there not being much volume of debris and it not running very far I’m guessing it was within the new snow/storm interface and didn’t step down to any buried PWL."

We rode through first and second Yellowmule at Buck Ridge. There was a natural avalanche below the cornice line on the headwall above second Yellowmule that broke within the last 12 hours as it was not covered by any new snow. From a distance, it looked to be ~200' wide and broke 1-3' deep. I believe it failed just under the storm snow, not of deeper weak layers, but a very large cornice, hang fire (snow that didn't avalanche above the crown), and ongoing loading from snow and wind made it unsafe to investigate more closely.

The storm total farther back in the area was 20" of thick snow. Strong winds were creating heavy drifts in many areas. Human-triggered avalanches are likely on steep slopes, especially those loaded by fresh drifts. We dug one pit near the entrance of 2nd Yellowmule, we saw the buried weak layers, but they did not react in our stability test... We tested the snowpack for scientific interest. We planned to, and did, stay off steep slopes and the runout zones of slide paths and recommend that folks do the same until the storm is over and the snow has a chance to stabilize. The lack of propagation is a good sign for longer term stability, and I expect slopes to stabilize relatively quickly once the storm is over and wind-loading lets up. 

Today I toured up to Chestnut Ridge via Goose Creek Trail. I noticed many wind deposits on the upper ridgeline that were actively thickening from the gusty Western winds (roughly 25mph average at the ridge). I dug a quick pit at 7370' on an Eastern aspect under the ridgeline and got some very touchy results. My HS was 125cm. I got a CT4, sudden collapse, Q1, breaking within a thick layer of advanced basal facets. The slab that came off was 85cm in height and very cohesive. Between the obvious wind loading near the ridge and my test result (which, I'm sure I could have replicated based on my probing of the area), our party decided to stay completely out of avalanche terrain and ski a few runs on mellow meadows and glades nearby. Minimal new snow fell during our tour -- just broken skies and a healthy dose of wind moving through the area. Stay safe out there through this storm cycle!

We snowmobiled and skied near the Throne and stayed on slopes less than 30 degrees and out from below any slopes steeper than 30 degrees. At 11:00am at 7,500' we measured 14" of new snow equal to 1.2" of snow water equivalent. It was snowing one inch an hour and wind was moderate with strong gusts. Avalanches of new snow were likely on steep slopes and very likely on steep wind-loaded slopes. Conditions will get more dangerous as more new snow is expected over the next couple days. We dug a pit at 7,500' on a northeast aspect. HS was 157cm and we did not see any reactive or concerning weak layers, but the new snow and wind-drifts are enough to create large, dangerous avalanches.

Our party toured up to Prayer Flags this morning. We found 10-15 cm of low density new snow drifted much deeper in some places. Their were moderate winds out of the west to north. We stomped small soft slabs of wind drifted snow at the ridge breaking 10-15 cm deep and only 5-10 feet wide at the new/old interface. We also witnessed small point releases on very steep slopes and around cliffs triggered by spin drifts. We Found cracking in the new snow on both East and West sides of the ridge between Beehive and Middle. On unprotected solar aspects you could feel a sun crust under the new snow. Places unaffected by the sun were bottomless feeling. We had no note worthy results in our quick test pit.

Dug a quick pit on a west aspect on the west side of Woody Ridge. HS was 178 cm. ECTN 29, 1.5’ below surface on 1.0 mm rounding facets. Skied off the west side of the ridge. The snow was more wind drifted towards the bottom of our run, 4-6” wind skin in spots. We didn’t see any signs of avalanche activity. Snow started falling lightly around 1400.

On Saturday (2/18) we toured into Maid of the Mist and dug a pit on a northern aspect at the base of the skinny maid. Our results indicated that where there was wind loading, it was very likely to fail and propagate. In addition to the ECTP 1 on the wind slab, we noticed shooting cracks on isolated pockets of wind loading. 

A snowmobiler triggered a 6-10" slab on a wind-loaded slope on the south side of Mt. Abundance near Cooke City on 2/18/23. Video shared with GNFAC via Facebook and YouTube.

Triggered a couple small slides on the cornices that typically form in the corridor here: 45.91263, -110.95506

wind was blowing in strong gusts and it started snowing very heavy around 1pm  

super reactive. Approved the small slope and the whole thing went. It was only 2-3 inches deep. Likely from wind blown today and some of what was falling. It did run for about 40-50 wide. Nothing that would bury a person but definitely a telling sign. 

My group and I went up into Beehive Basin to do some sub-alpine skiing into Middle Basin as well on some of the east aspects in Beehive. We went in feeling good about the snowpack given recent observations and the forecast, but before dropping into our first line on the Middle/Beehive ridgeline we dug a pit on an E aspect at around 9500'. There was good depth in the area (HS 190 cm) and the upper few feet of the snowpack was mostly right side up with faceted snow towards the bottom that appeared to be gaining strength. We pulled a shovel shear, which yielded unremarkable results and an ECT with a result of ECTX. We had a great day out there skiing and felt good about what we saw!

We rode up to ski hill and dug a pit at the top. East-northeast aspect at 8,050'. HS 164cm and ECTN21 on surface hoar 40 cm down. Then we rode up along the ridge to Airplane Bowl and dug near the ridge north of the saddle. East aspect at 9,300'. Here HS was 144cm and we had ECTN20 on facets 40 cm down. We rode down Airplane Bowl and around the north end of Lionhead Ridge into Targhee Creek. Wind was light to moderate and forming small plumes of snow along the ridge.

We did not see recent avalanches aside from one previously reported snowmobile triggered slide at the top of Airplane Bowl. It was 30-40 feet wide and maybe 6-8" deep. It appeared 3-4" of snow fell 3 days ago. This snow was blown around by the wind and created some small, isolated drifts that have become more stable with time and now seem unlikely to be triggered.

Went for a quick tour up Ellis today. Dug twice along the ridge, both pits had ECTN 12-14 under the new snow. Top of Ellis was worked by the east winds. Worked my way down carefully on the southern end of the Meadow area. Overall the stability seems to have improved since Doug and Ian were up earlier in the week.
 

We rode up Portal Creek today to check motorized boundaries.  Riding in the meadows and trees in the basin's north of Golden Trout lakes was decent and not caught any wind.  All of the ridge tops appeared to be heavily scoured or wind loaded, depending on aspect and we noted several small wind slabs on the N-NE ridge tops directly above the lake.  They appeared partially filled in so we're likely from a few days ago.  We did not see any recent tracks climbing much above tree line, likely since everything had been so wind affected higher up. 

We were in the Lick creek area and did an ECT test,  the new snow appeared to be bonded well but on ECT 20 we got a clean sheer about 30 inches down across the column. We headed back to lower angle terrain.

We were snowshoeing up Grassy Mountain on Feb 15. We were following someone else’s tracks up to a SW facing slope between 35 and 40 degrees at 6400 feet (directly across from Bridger Bowl). We realized the other person had probably turned around because of this crack in the snowpack directly above a gully with terrain traps. We did the same.

Rider triggered avalanche on crown butte. Saw and heard reports of small rider/skier triggered wind slabs North of Cooke City.