Snow Observations List

We skied a 25 degree west slope today on Woody Ridge.  No sign of instability.  No wumphing or cracking.  No wind effected snow, in forest

5 degrees,at 100pm, light breeze.

HS 110-115 cm

new snow 30 cm. fairly cohesive but not bonded to old-variable

Layer of facets below new snow and above hard layer 60cm deep

Hard layer 10-15cm thick

facets below hard layer

The snowpack depth was variable.  New snow not well bonded to old snow in places

we climbed to 9550 and stopped as terrain got steeper

Coverage was good.  Very good skiing

I might add that several times during the day we commented on the difference in red flags we experienced from Beau's report the day before. We were both S. of Cooke, but differences in that we were in wind-protected forest most of the day, although in meadows above about 9K, more importantly, perhaps is aspect - we were W. and I think from photos, Beau was on an E. aspect. Although we didn't get collapsing or shooting cracks, we all recognized the poor snow structure we were on and we pulled skins when slope angle approached 30 deg.

Average snow depth was only in the 110 cm range and the terrain we were in looked very different from that in a year with a normal snowpack. Sill some snow-snakes and staubs concealed barely below the surface.

Ski toured south of Cooke City today to try and take stock of the recent natural avalanche cycle.

Avalanches were observed on all aspects, except south.  A few photos attached.

Of note, many crowns have quickly disappeared, with additional wind loading.  Particularly from recent N, NW winds.

Still getting widespread collapsing and cracking, particularly above about 9300'.  

One collapse, in relatively wind sheltered terrain, photo attached, was wild in that the cracks shot away from me about 100' relatively slowly, and then circled back in a big loop!  About a 3 second symphony of movement in the snow.  

Higher in more wind exposed terrain, the collapses became spooky, with Pencil hard wind slab in places.  There the collapsing was much louder- and communicated the large mass of snow above that weak layer.  A couple of times they made me jump, and I am typically quite comfortable with whumpfing when I am in safe terrain.  It's just humbling when you feel the energy of a very large mass of snow move.

Good to give those hard wind slabs an extra wide margin though, because I've once seen a section of flat ridgeline avalanche into a connected steep slope (deep slab/ hard slab in the Wasatch, 20yrs ago).

From email: "Lots of hand pits to look for the SH and only found it in open areas at higher elevations. The SH was 10-15mm in size, well intact and "sturdy", overlaying small-grained facets. In hand pits, the column would fail upon isolation, yet the slab wasn't very cohesive, even in windloaded areas. The hand pits were failing on the facets underneath the SH. Some cr, co at higher elevations.

One crown on the Middle Siren, probably part of the last cycle. 

Winds were L-M out of the south and S-1 snow starting at 11am. 1cm of new by end of day. "

Dug pit in a protected area in the trees around 9250’. A layer of soft new snow (about 25cm) was sitting on top of  a base of facets. Total snow depth 1m. Thin crust around 50cm. ECT and CT broke near the new snow/facet interface. 
 

In other areas, we saw a thick layer of surface hoar buried about 15-20cm deep. Large striated depth hoar was also observed at areas with snow depth <1ft. 
 

A potential crown was observed from a distance across republic creek on the south side of the drainage.  
 

https://snowpilot.org/node/58881

From email on 01/13: "From Miller Ridge today, I had a brief look into Sheep Creek, and to the mountains south of Cooke City, and observed 7 fresh slab avalanches (that happened in the last 1-3 days).  Will send photos of them later if I can get better views.

Most of them were on NEerly aspects, and appeared to be on the new/old Jan. 5th interface.  Mid and upper elevations, most commonly in wind loaded terrain.  Some propagating a few hundred feet wide. "

From email: "Toured into Republic creek with our class. Noted two D2 soft slab avalanches. One on a west aspect and the other on an east aspect at about 9000'. I estimate the crown was 15-40cm deep and likely ran on the same layer as other recent avalanches in the area. 

ECTP4 down 25cm on SH in one pit where there was recent wind transport and a more cohesive slab. Other pits in sheltered areas produced ECTN's on the same layer. HS 100cm, 8200', W aspect. Some localized cracking and ,collapsing."

Saw this avalanche today on the North end of Sheep from the Round Lake warming hut. Natural or possible snowmobile trigger 

Saw a natural avalanche on the east side of Henderson from the Lulu Pass Rd. Also observed a natural on the east side of Sheep Mountain. These likely happened during or near the end of the last storm on 01//10. 

From email on Jan. 12th : 

"The avalanche is on Miller Ridge, on an easterly aspect, around 9k'.  Crown appears to be about 2' deep.

I toured around on SWerly aspects, near Daisy Pass, up to 10k'.  

Widespread collapsing and cracking.  The collapsing was not especially audible, but the cracks often shot out 50-100' spectacularly- while setting an uptrack, and on descents.  

The collapsing and cracking was much more pronounced above 9600', and was happening on the new/ old snow interface.  This was somewhat surprising in this location, because the old snow surface was Very heavily tracked by snowmobiles prior to this storm cycle.

New snow:  was finding about 40cms settled on top of the Jan. 5th interface.  Slightly upside down with the wind from last night.  4F- over F.

Weather:  cold temps.  It cleared for about 45 minutes late morning, and then clouded over again.  Moderate winds from the west, but strong and blustery at times, creating temporary white outs."

GNFAC note: the avalanche on Miller was previously reported here.

Broke loose a slide just below the radio tower standing above the crown. Broke about 30 cm down on a layer of weak snow. 

Also saw very unstable snow pack at the top of the main gully below the radio tower, large cracking and settling. Snow propagated across but came to a stop before a slide began. Large chunks of snow and debris broken off from the cornice to above main gully. 

From email Jan 12: "Natural avalanche on the Fin of Mt. Republic observed this morning.

The timing of it looks to be about 36-48hrs ago.

Looks like it might have started at the new/old snow interface, and then stepped down into deeper layers mid face.  

Quite an impressive avalanche!"

Collapsing, shooting cracks (30ft+), and whumpfing noted while breaking trail on the W aspect of Henderson. Frequency increased with elevation. Natural avalanches noted on E faces of Miller, Republic, and Henderson. Also natural avalanches on SW face of Scotch Bonnet.

From email: "From this morning. Looks to be 1_1.5' deep. Maybe  a few different ones based on what I can tell." 

From email:  "Approx 35 cm new snow. W aspect 9750’ HS 117  ECTP 4 and ECTP 1 35 cm down on surface hoar. Trace of new snow today and getting colder fast. Shooting cracks were common outside the skin track up to 20ft and collapsing was frequent. "

Yesterday (1/9) touring north of Cooke City I felt some large collapses and cracking on a heavily wind loaded, mid elevation slope. There was about 4-6 inches of new snow that fell throughout the day. 
 

Accessed Woody Ridge from Republic Creek, approximately 3 mi up.  Turned around on a west slope at 9000', due to time of day.  8 degrees air temp,  

Snowpack skied well and was supportable - 6-8" of new that seemed well bonded to old snow.  2 perceptible layers when probing with a ski pole.  Lower layer much harder.  

Downfall is still a hazard - not completely buried, but skiing was remarkably good, considering.  

Mostly overcast day.  Occasional wind gusts out of the SW, but mostly calm and cold.  

I saw debris from an avalanche in one of the southern Woody Ridge gullies. The slide appeared to be a recent windslab formed by the new snow over the past few days. Best guess it happened yesterday, and it appeared to be natural. The crown appeared ~8-16” from a distance, and was on the skier’s left side of the gully, the side that sees loading from wind out of the south. It ran a few hundred feet down the gully. 

We were the first to arrive at the bottom of Lulu Pass this morning and observed 3 natural avalanches on E and NE aspects of Henderson Mountain. The turn off from HWY 212 towards Lulu pass had received 4-6in of low density snow the night before, the bottom of Henderson Bench had only received 2-3in, but some areas on the trail had pockets of blown in snow around 6in deep in drifts. Hand pits quickly showed that the new snow was sitting on our thin base of faceted snow and surface hoar. The avalanches appeared to release from small cornice collapses on the ridge of Henderson Mountain. 

We went south of Cooke City today and toured up Republic Creak towards Woody Ridge. Stepping off the skin track ski penetration was quite noticeable, sinking 6" or more and breaking trail through loud faceted snow. We began ascending the slope and found an area on a northwest-facing slope at 9300' to dig and assess the snowpack before continuing on steep potentially wind-loaded terrain. In our snowpit, we had ECTN 21/ECTP 22 results, we did another stability test with ECTN22 results on the same layer. 

We continued until we reached an area that had been previously wind-loaded and a cohesive slab could be felt. The depth of the snow never rarely exceeded the length of a ski pole so we were able to probe the snow to assess whether or not a slab was present. In one snow pit, we saw propagation, ECTP21, but just ten feet over stability tests yielded ECTX results. Walking around the area it seemed like this was an isolated case where a slab was present. 

After all this assessment we felt it was appropriate to enter avalanche terrain while maintaining good travel protocols by only exposing one person at a time on the slope and keeping eyes on each other from a safe location. While exiting the creek bottom I did remotely trigger a very small slab while crossing a snow bridge. 

Still getting collapsing/ whumphing of the snowpack in isolated areas around Cooke City.  

We experienced about 4 good collapses on Monday north of town (with approximate diameters about 25-30').

And noted where a natural cornice fall had triggered a small slab avalanche about 30' wide.