Snow Observations List

Surface hoar south to south east aspects, potentially more aspects, will confirm later this afternoon. 

On December 31, 2022 a snowmobiler was killed in a very large avalanche north of Cooke City, MT. The avalanche occurred near Daisy Pass on Crown Butte on a southeast facing slope at 9,800’. Two brothers (age 17 and 21) from Washington were snowmobiling uphill on adjacent slopes. The older brother was climbing a steeper slope and triggered the avalanche 100-200’ below the top. He was carried 600 vertical feet and buried 5 feet deep. The buried rider was wearing an airbag pack that was not deployed. Both riders had shovels and probes. They were not wearing avalanche beacons. A nearby group of riders rode up to the slide within minutes after it happened, saw a buried snowmobile and began to search for the rider. One rider from that group went into Cooke City to alert Search and Rescue. The buried rider was located with a probe line an hour after the avalanche happened. He was unable to be revived with CPR and AED at the site. Our deepest condolences go out to the family, friends, and those involved.  

The avalanche appeared to be 2-4' deep, 500' wide, 600' vertical, and broke on weak snow near the bottom of the snowpack. AMu-HS-R3/4-D3-O

Yesterday afternoon (12/30) we rode to Henderson Bench and dug a pit at 9,600' on a NE facing slope. HS was 188cm and we had ECTN22 and ECTN23 at 146 cm above the ground. New snow from the last week was over a foot deep and it was snowing steadily, an inch an hour at times while we were out. Snowfall tapered off in the evening, then this morning dropped 4" in town and more in the mountains.

Today we were rode north of Cooke City. We rode over Lulu Pass and dug a pit at Goose Creek at 9,500' elevation on a NE facing slope. HS was 216 cm with 40cm of new snow from the last couple days. The top 14" of the new snow weighed 0.7" snow water equivalent. We got ECTN 25 and ECTN 27 at 150cm above ground on facets sized 0.5-1mm.

Later we rode over the saddle between Sheep and Scotch Bonnet and saw an avalanche that appeared very recent, and likely triggered by a snowmobiler. It was on a west facing slope at 10,000', and was a hard slab 1-4 feet deep and 150' wide, ran about 200' vertical. AMu-HS-R3-D2-O. This was a clear sign that weak layers exist, especially where the snowpack is relatively shallower, and recent snow has been drifted into thick slabs that are unstable over this weak snow.

skied both NE, S and SW aspect lines in Sheep Creek Basin. No signs of wind loading where we traveled, up to 9600’ at the saddle between Sunset and Miller Mountain. There were light winds (M gusts). 8-10” of new low density snow.

Dug a pit on a SW aspect, 8480’:

160cm deep

CT22Q2 Down 40, EctN 25 down 40

ECTP28 down 85

Pole probing confirmed the presence of the top persistent grain layer throughout the landscape, although the associated crust was not widespread. 

We also experienced a Whumpf at 45.03667, -109.96733 On a SW slope, 9000’ in a shallow area (125cm depth). 

Snow above collapsed into the trench from my sled, looked to have broken on a weak layer about 1.5’ down. 

From email: Dug a pit on a NW aspect near the bottom of Lick Creek. Saw sugary facets 50 cm down from the surface of the snow. Perfromed an ECT and got ECTX. 

Skiing from Mt. Zimmer Yurt on 12/30 and 12/31, we found two weak layers of small near-surface facets within the new snow at around 30cm and 40cm deep. The layers appeared to be rounding and healing but were somewhat reactive. In our snowpit on an east facing slope at 9,400 feet we got ECTN results on these layers, but in a PST test, the 30cm deep layer collapsed at 30cm into the cut. This made us wary of skiing avalanche terrain and we avoided steep open slopes. We did ski some small isolated steep terrain features and occasionally had this storm slab break off underneath us, but it did not ever propagate beyond steep, convex features such as spines and pillows.

The attached photo shows a small snowboarder-triggered avalanche from 12/31 on a southeast facing slope at 9,000 feet that broke on the 30cm layer and stepped down to the 40cm layer. The intermittent sun on 12/31 seemed to be increasing the reactivity of the storm slab on sun-exposed slopes. The snowboarder was briefly caught in the sliding snow but maintained his footing as the snow washed past him.

On the way back to Lionhead.  Came upon this recent avalanche.  Rushed up to the group of 4 guys.  They were fine, not the guys who set it off.  The group of 6 we passed going there set it off.  The group of 4 said they saw these guys ... all on the hill at same time, stuck and climbing around the stuck guy.  All were okay but I hear one guy was shaken up. 4-5ft deep at break by 200-300ft wide, ran 400+ft.

Today we toured up above Blackmore Lake to ski a E-NE facing meadow. We observed about 5-10cm of fresh snow in the area with minimal wind loading. On South aspects, the recent sun crust was much more supportable than in more shaded and protected areas. There was evidence of past wind loading at our pit location, which was on a slightly more north-facing ridge than the meadow we skied. Although this recent crust was evident on all aspects, it was quite soft and breakable on protected aspects. An ECT test revealed instability above a crust layer at 130cm in the snowpack (ECTN22@130). The shear quality was clean at this interface and, when the shovel was placed behind the block, it popped off quite easily. With the significant temperature shifts adding some complexity to the snowpack, it will be interesting to see how the stability progresses at these crust interfaces. 

Toured into middle basin and middle peak today. 5-6 inches of new snow. Temps in the high 20s. Wind E and NE - moderate at ridge top. No obvious signs of instability throughout the tour. S1 graupel falling at 1430.

Toured up to the east face of Mt. Blackmore today. We observed two small natural loose dry avalanches occurring right around noon on the new/old snow interface at about 9700' on the E aspect. The largest one ran about 200 feet down into the bowl. 

We observed a hollow snowpack on our ascent and dug a pit at 9600' just below the northeast ridge. We found several weak layers that were fracturing beneath two well-defined crusts. We got a CT2 @ 135cm, CT11 @ 130cm, CT13 @ 118cm, and CT15 @ 115cm; in our extended column test we got ECTP15 Q2 @ 130cm.

Went to jones creek yesterday, 20 cm facets underneath everything it seems. Depth where the wind could reach it(sw aspects mostly) was averaging 60 cm, 100 to 120 cm where it was more protected. Not a lot of weight yet but columns failed on isolation. No cracking or whumphing

Climbed up to the ridgeline above Hebgen lake and dug on a SE aspect at ~8800 ft. HS 112 cm. Found around 8 inches of new snow at upper elevations and both of the weak layers we’ve been concern about. ECTN11 x 2 on the facets just beneath the new snow and no results on the lower facets. No signs of instability observed throughout the day. Not quite enough of a slab here above the upper facets, but definitely wouldn’t trust them in places with a wind load or more new snow.

Visibility was good enough so we headed into the weather station and dug on the E facing slope. The instability was concerning and we tip-toed out onto the slope with an inclinometer in hand. It was thin (HS 105) and the 2 prominent weak layers were there: ECTP11 on the upper one and ECTP12 on the facets/depth hoar. We then rode into Sage Basin and found natural avalanche activity on the N facing side. It looked like the slope fractured on the upper layer and on steep terrain it broke to the ground. We dug another on the east end of Sage and had a 176 cm deep snowpack that was unremarkable. On the way out we stopped at Consolation Hill (SE facing) and I got a big whumpf with a body slam as footsteps were just sinking to the ground. This snowpack was thin (HS 87) and it broke on the depth hoar at 35 cm (ECTP11).

I toured up toward Divide today, mostly just to get out and take a peek at the snowpack. The storm overnight dropped 10-20 cm up high, and it was getting moved around a fair amount by the wind. 
 

I dug my first pit on an east aspect at 8900’. The snow was 165 cm deep here, and there was a visible dark band 20 cm down that was pencil-hard and 1 cm thick. I got an ECTN13 on this, failing on a thin layer of facets just below the harder snow. I also got an ECTN 17 on another thin layer of facets another 20 cm down. When I filled the pit in, the top 20cm readily came off of my extended column, and the rest stayed cohesive to the ground as I tipped it over, save for the rotten stuff at the very bottom of the snowpack. 
 

I dug another pit at 9550’ on the SE aspect of Divide. This one was 145 cm deep and had a similar structure to my first one, and gave me ECTN14 and ECTN18 on what I believe to be the same layers, although the firm band of snow 25 cm down didn’t have as obvious of a layer of low-density facets beneath it. I did get a clean, fast propagation 60 cm down at ECTP22. The slope I was on was only 28 degrees, but I bailed to head home and eat cheesecake instead. 

Today in Beehive we found blowing snow which has grown the easterly cornices significantly since two days prior when we were there as well as pillows of wind drifted snow on leeward slopes. In wind protected locations we found excellent skiing. Previous tracks were filled in with right side up snow that seemed to be bonding well to the previous snow surface. In our pit on a east aspect at 9,000' we found two very thin melt freeze crusts in the top 30cm that produced ECTN as well as facets on the ground that produced no results. On a west aspect we felt that same melt freeze crust buried under the new snow breaking and hooking up our skis. A quick hand pit showed this crust to be a little thicker and harder.

Natural avalanche from the top of the popular snowmobile climbing spots on McDermott Hill in the Flint Range near Philipsburg.  There have been several close calls and a fatality in this same path.  It is named for the person who was killed in an avalanche there in the 70s.  It appeared to be a wind load on the ridge that initiated the slide.  In the background of a janky video, it appears there were other naturals as well.  The slide ran an estimated 800 ft, but no other information was obtained.

Snowmobile club members texted me that they triggered a 3' deep slab, that ran 100 yds., from connected terrain in Frog Pond Basin.  It sounded like a heavily wind loaded slope.     

Pit Location: E / ESE Aspect  |  10,000'  |  220 - 230 cm snow depth  |  Near Treeline  |  28 degree slope

Weather at 14:15: OVC  |  S1  |  Winds Strong out of the S / SSW

Test Results:

16cm down from surface; ECTN2 PC and ECTN3 PC at the newer snow interface, still a fairly soft slab without a lot of cohesion in this particular area

71cm down from surface; ECTP21 SP and ECTP23 SP, broke on the same layer of small facets (~0.5-1.0mm) noted in 12/27 forecast below this week's more recent storm snow

Mostly minor cracking observed at the snow surface during today's outing, a couple of shooting cracks were observed in steeper wind drifted snow in more exposed areas