Snow Observations List

We rode out to Lulu Pass to look at the few avalanches that were reported yesterday on Henderson and Fisher Mtn. Today we did not see any avalanches that weren't previously reported, other than one small, but thick wind slab on south facing slope of Scotch Bonnet (photo). At least the avalanche on Fisher and one on Henderson broke near the ground (pics attached). Some slides were heavily refilled by drifted snow, so it was hard to tell how deep they broke.

Yesterday I saw a wide slab avalanche up on west Woody Ridge from town (photo attached). It happened late on Wednesday or overnight during or after the strong winds and snowfall.

We dug a pit on a north-northeast facing slope below Fisher Mtn. (on Rob's Knob). Snowpack was just over 3 feet deep with a stripe of surface hoar in the middle. Generally 1F to Pencil hard slab above the SH. Facets near the ground were 2-3mm and rounding. We had ECTP22 on the surface hoar and ECTN22 and PST 25/100arr.

Despite the generally hard and rounded facets near the ground, recent avalanches are a sign that those are a problem in addition to the surface hoar.

Clear and mostly calm today. A few rollerballs on southwest aspects.

Overall, the recent avalanche activity is a sign that the early season weak layers are a problem to watch going forward. Danger and likelihood of avalanches may decrease in the immediate future with a break from loading, but we need to be thinking about these layers when future storms add up.

Went out to have a look in the northern Bridgers today, hopeful that the moderate rating for the Bridgers today would lead to some fun lowish angle action. 
Dug a pit at 7600 ft on a NE facing slope. Full propagation on isolation of the column on the layer of concern about 16 inches down in this zone. Went a little higher up and got a big whumpf and that was all I needed to bail on even the lower slopes. 
 

Light winds and a sunny morning were quickly having an effect on the snowpack at history rock. Around 40f temps all day, with a moist, gloppy, snow surface. A quick dig in the top meadow showed the storm/windblown snow was moist down to the crust formed during our last high pressure, and the basal facets were also moist up to around 30cm from the ground. We saw no signs of instability in the less skied areas of the top meadow, including those that had been recently wind loaded.

From email: "Maiden Voyage to Goose Lake for the season today. Lots of wind drifted snow everywhere and challenging riding conditions. Performed Stability test on shoulder of Mount Fox NE facing slope at 10,300'. HS 180cm. ECTP2 40cm down on Buried Surface Hoar. ECTP 23 90cm down on MFcr with 1-2mm Facets. Saw several recent wind slab avalanches in steeper windloaded terrrain around Goose Lake, but limited activity was seen on Henderson. Lots of co/cr while touring on Mount Fox. D2 avalanche on east facing Mount Fox that appears to be on the SH layer, triggered by a cornice drop." 

Today, we rode up to The Throne for the first time this season. We parked at the motorized boundary and toured up the east face. The road riding was good but there were certainly more dirt patches on the way out, than in, with the warm temps.

We dug two pits on the east face as we ascended. At 7950' we had HS: 78, ECTN13 + 23. At 8140', we got HS: 97, ECTN 30. We toured up the ridge and moved over onto a north aspect. There we got HS: 94, ECTN 30. We observed no cracking or collapsing. Weak layers still exist at the bottom of our snowpack, but we were happy to find that these weak layers in the Bridgers seem to be not quite as weak as in our other zones.

We had good visibility and were able to get eyes on two avalanches that occurred naturally during the major wind event yesterday in the bowl south of Naya Nuki. The largest of which was a R2-D1.5 that broke in the new snow. We also got eyes on a natural avalanche (R2-D2.5) that occurred yesterday on Saddle Peak.  

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.