Snow Observations List

Toured up Flanders Peak this morning—a beautiful day with clear skies and no/light winds.

During our ascent, we observed widespread wind effects above 8800'. The west-facing ridge of the drainage was scoured of snow, while wind loading was observed on E/SE aspects between 8800' and the summit. 1-5" thick wind slabs were widespread, and were especially of note at lower elevations in the east-facing trees; increasing depth and stiffness as we ascended and on Flanders' E shoulder. Got a few small whumpfs along the E shoulder while ascending, but no other signs of instability on the day. Several small test slopes we traversed along the ridge did not show signs of instability when we tested them.

The power of the winds was emphasized by the scoured west side of the East Ridge of the Main Fork.

We skied the slope in the trees south of the summit and dug a pit on a SE aspect @ 9530'. Skiing quality was low. Snowpit depth was 72cm. Test results were CT11 SP, ECTN8, PST 44/100 (End).

Quite a few natural avalanches observed north of Cooke City today.   Photos attached of:

1:  NE facing, 10,000, Miller Ridge

2:  E facing, 9900', Bull of the Woods Pass

3:  NE facing, 9700', Miller Ridge

4:  E facing, 10,200' Scotch Bonnet Mtn.

5:  E facing, 10,000 Mt. Henderson

6-8: NE- N facing, 10,000' Mt. Henderson

9:  NE facing, 10,000' Sheep Creek.

There was also a large avalanche event on the E aspect of Fisher Mtn, which I didn't photograph.  But there were some other skiers nearby who likely had a good view of it.  

Also, we had 4 large collapses today.  One on a southerly aspect, and the other 3 on NE aspects.  All around 9800'.

Observed from Flanders this morning. Presumed recent natural slide around ~9950 ft. on a E/NE aspect. Hard to tell from a distance, but cornice interference and/or wind loading are possible culprits. Poor image quality, but there may be more debris piles along the ridgeline to the south.

HS-ASr-R1-D1-I

Fraizer Basin, 8500', North facing, 35-37 degree slope, 1pm

30' wide, 6'' deep, ran 150', In the love chutes, Fraizer Basin 

1Finger wind slab sitting on a 4Finger hardness break.  Triggered from 30' above the crown, ran slowly.  A majority of the slab rode back up on the surface 50' below the crown.  Bed surface felt like small grained facets under skis, didn't look too close. Small and localized cracks and collapses were felt and seen throughout the day in the same location. 

I toured to the East shoulder of divide park today 

It was very windy and snow was being transported everywhere…..especially on the high peaks 

I dug a pit on the SE shoulder of divide at around 9600’ and got a ECTP 14 on the persistent weak created during the long dry spell layer buried from this weeks storms.  50cm of snow had fallen up high in the main fork of hyalite since Sunday night.  Total snow depth is 115 cm

Skinned up Beehive Basin, dug a pit on the edge of Tyler's and climbed up to the prayers flags. Winds picked up as we approached the ridge, moving quite a bit of snow. Skinned along the Beehive-Middle ridge for a little ways and then skied down towards Middle and skinned along above the rollover for a while. Dug a pit and returned the way we came.

Snowpit in Tyler's (W facing) was 80 cm deep, with an ECTP13 on the facets mid-pack. Snowpit on the Middle Basin side (E facing) was 120 cm deep, with an ECTP 14 on the facets mid-pack.

On our way back along the ridge we found a small natural windslab that had broken below the cornice during the hour since we had been there last - it broke up to around a foot deep, 20 ft wide, and ran about 15 vertical feet. This was the only avalanche we saw today.

Got a few little cracks in switchbacks along the skintrack while climbing out of Beehive, but no other cracking or collapsing. 

My friend and I toured in Beehive this morning.  Was calm early but the winds picked up late morning and were whipping around pretty good as we left mid-afternoon.   Dug a quick pit at ~9300 ft along the upper east side of the west ridge of Beehive Basin (lower end in the timber before it gets exposed in the upper basin).  Snowpack was ~120cm deep, approximately half of that being from the last storm series.  We got an ECTP11 that was a smooth propagation which failed ~65 cm up from the ground at the interface of the new storm snow.  This reinforced the instability we expected to find and we stuck to a few laps of the smaller / gentler east facing meadows.  Skiing was great though!  With the wind today I’m sure the instability will only get worse before it gets better…

Lots of wind slabs south of Cooke today. Strong wind all day and lots of blowing snow. 

From FB messenger: “Bottom of Slats area. Buck ridge. 
NE slope/hole wind loaded. Sled triggered, 315 pm Sunday Dec 15, 2024”

Rode along Buck Ridge, through 1st, 2nd, and 3rd Yellowmules, with good views across Buck Creek and into McAtee Basin. New snow depth increased as we rode from the parking lot to the top of Beaver Creek, from ~4" to 12". We measured 12" of new snow with 0.7" SWE in 1st Yellowmule.  We saw two avalanches. One was a storm slab avalanche on the far (southwest) side of Buck Creek - broke 2-300 ft wide and ran ~500 vertical feet. The other was a smaller slide in 3rd Yellowmule (~100 ft wide and ran ~200 vertical ft). There was not much wind effect.

We crossed through the head of McAtee Basin into upper Bear Creek. While riding on a low angle ridgeline, we remotely triggered a slide that broke approximately 200 ft away in a gully. It failed ~18" deep on facets underneath the snow that has accumulated since Sunday. It broke in several pockets, totaling around 200 ft wide. There was 12" of new snow at the crown, with 0.7" SWE. The slab contained 1.4" SWE total (which accumulated since Sunday). 

Before triggering the slide we experienced no cracking, collapsing, or other clear signs of instability. 

Dug a pit on the east facing slope around 7800'. The snow was 60 cm deep. We got ECTN11 and CT12 RP 15cm down on the old/new snow interface, ECTN16 25cm and CT19 25cm down on a crust.

Also dug a hand pit on a south slope at 6800' to test the new snow and it didn't break easily or cleanly.

We didn't observe any whumphing or cracking.

Triggered a small slide (r2 d2) in a north east facing chute at around 8300 ft. The slide was triggered on a ski cut through a wind loaded drift and propagated about 15 or 20 ft wide. It about 6 in deep on the edges and two feet in the loaded area. We observed several other signs of instability throughout the day, most wind loaded terrain was touchy and easy to rip off with slabs anywhere from 6 in deep to two or three feet deep. All signs of instability originated from the interface between the new snow from the last few days and facets from the last high pressure system. 

The clouds broke briefly around noon today in Cooke City. It looks like the Fin slide naturally in the past day or so. It looks like two sections of the face slid, one from the top, and one lower and to the right in the photo. 

The old snow surface from the first two weeks of dry weather in December is the main weak layer in the snowpack. It is easy to find on all slopes just under the new snow and two crusts. It's generally buried about a 12-14 inches deep.

We got a range of test scores (mostly bad) of ECTP2, ECTP3, ECTP13, and ECTN. We experienced a few collapses, but it was not widespread. No cracking.

Avalanches - we got above the clouds into the sun and could only spot one avalanche looking towards Mt Jefferson in Rock Creek

My gut says that avalanches aren't too easy to trigger; HOWEVER, all the signs are there and can't be ignored. Some collapsing. A prominent weak layer of facets. Mostly poor test scores, recent loading (1.5-2" of water), and one fresh avalanche.

For those reasons we rode like the danger was CONSIDERABLE....which it was. 

Riding and coverage is quickly improving. Above 9000 ft, there's a decent base under the weak layer. Rocks and stumps are still easy to find and we were bumping them all day long.

Around 5" of fresh snow lay on top of the snowmobiles this morning in Cooke City. We rode up to Daisy Pass to visualize terrain and got eyes on Crown Butte. On the north side, we noted the crown of a wind slab avalanche (R1 D1) that broke during the storm cycle. We then rode back down and toured up Henderson Mountain along its SW flank. Skies cleared throughout the day and allowed for great visualization of terrain north of Cooke. We got eyes on Miller Ridge, Crown Butte, Henderson Bench, Scotch Bonnet and Sheep Mountain; we did not note any other avalanches outside of the small one up on Crown Butte. We saw extensive cross-loading in the bowl of Henderson Mountain and on Miller Ridge. 

We dug snowpits on SW and S aspects on Henderson. We noted buried facets a little over a foot deep on our pit on the SW and we got an unstable test result in our snowpit on the S aspect (ECTP 25) on a facet/melt freeze crust sandwich. 

Most notably, as we entered non wind-effected, upper-elevation terrain on Henderson, we consistently triggered many localized collapses and heard audible whumpfs, indicating persistent slab instability. 

These avalanches were reported yesterday 12/15 by ski patrol who heard them run and saw debris around 1230. They broke naturally towards the end of a period of heavy snowfall that totaled 10"=1.22" SWE. Photos taken 12/16 at 1045-1100.

Today, we rode up to the base of Henderson and toured up to the bench to check out the crown of an avalanche that occurred yesterday. The avalanche was remotely triggered by a skier from 50' away. It was about 100' wide, ran 50' vertical, and the max depth of the crown was 2.5'. It fractured on the interface between the new storm snow and faceted grains. This was a heavily wind loaded area with an HS of 179cm. Strong westerly gusts and heavy snowfall had nearly refilled the crown by the time we left. 

We then traveled further up the bench to a north facing aspect and dug again. Here we got an unstable test result, ECTP 13, on a layer of buried surface hoar. Faceted snow exists at the base of the snowpack but our main concern on non-wind loaded slopes is layers of surface hoar and near-surface facets buried about 50cm deep. It was snowing and blowing throughout the day, and with continued loading, we expect to see collapsing, cracking and signs of instability tomorrow. 

Dug on a NE aspect on The Ramp at about 8500’. HS was around 100 cm but varied quite a bit. There’s a layer of very weak facets about 40cm down from the surface that are particularly concerning to me. The storm slab I observed yesterday is also still quite reactive, but the snowpack seems to still lack a significant slab on the aspects where I’ve been traveling. There was an abundant amount of cracking in the newer snow whenever traveling off a beaten path. In our pit, got results of CT3 SC and CT7 SC on the storm slab fracturing at the interface with sudden collapse character. The layer of facets farther down in the snowpack collapsed at CT10 SC. I also performed a PST on the weak layer of facets and the weak layer probated to end at 35/100 cm. 

Went out north of Cooke City today for some skiing. Dug a pit at 9980' on a southwest facing, windloaded slope with a slope angle of about 15 degrees. We found 105cm of snow. Our ECT gave us an ECTP29 55cm up from the ground on what seemed to be the buried surface hoar layer. It was snowing and blowing all day out there. 

From email: "Steve Harvey and I did a quick pit yesterday (12/16/2024) S. of Cooke in Republic Creek. E. aspect; 9.085'; 30° slope; HS 80 c; 12:30PM, Calm/cool (teens), Lt snow.

ECTN21; ECTP24 at 50 cm on buried facets. We declined to continue on slope.

We didn't perform a detailed profile, but generally, fist (new snow) and 4-finger above buried facets and progressively 2-finger to 1-finger below.

Noticeable Issues:

(1) Low and variable snowpack, 30cm or less under/near trees and on wind-scoured aspects and loading in fetch zones. Something to keep in mind as season progresses with  potential sweet spots in predictable places.

(2) Buried 50 cm facets/hoar that is essentially everywhere in Cooke City zone.

(3) We did not observe buried deep facets at the base of the snowpack."