Snow Observations List

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.
 

We rode along Buck Ridge and into the first and second Yellow Mule, then rode into MacAtee and Muddy Creek. Wind was calm to light and not transporting snow. There was signs the wind blew previously, from the north. We did not see any recent natural or human triggered avalanches. We dug a pit near the wilderness boundary in Bear Creek. It was 212 cm deep and we had two ECTXs, one of them propagated after an extra 5-6 hits on surface hoar 2 feet (55-60cm) deep. Overall stability was good and avalanches are trending towards unlikely. Slopes that have recently formed fresh drifts may remain unstable for a couple more days.

We toured up to the Skillet today. We noticed that winds from the NE had drifted the 4-6" of storm snow throughout Bacon Rind. The wind drifting is a bigger concern in the less sheltered areas of Bacon Rind. We dug two pits on a SE aspect at 7500', and 8,600'. There is a melt freeze crust sitting atop a layer of facets 4-6" below the surface, and this propagated easily in our pits (ECTP 3, ECTP 11). This is not a concern now, but it could be when new snow falls on this weak snow. Next, we dug a pit in the meadow to the south of the Skillet at 8,800'. We found surface hoar 14" below the surface, and it did not propagate in our test. In our pit at the top of the Skillet, we did not see propagation either. The terrain we were in today is trending towards stability. 

Saw debris and what looked like a crown line from a natural avalanche that probably happened a day or two ago in palace butte basin on a NE aspect above Arden lake. My best guess is 150ft wide crown, 1-2ft deep?

About 34 degree rollover, 14 inch crown.

We measured 14" of snow from Tuesday's storm with 1.6" of snow water equivalent. We were encouraged that we did not see any natural (or human-triggered) avalanche activity. However, there is a significant caveat to this. East to Northeast winds stripped the steep slopes of Carrot and Sage Basins that are regularly wind-loaded by the prevailing winds. Thick drifts in abnormal locations were evident. Ridgetop were we rode had pillows of drifted snow and we could see cornices running downhill on the SW side of Sage Peak that indicated the gullies and depressions were cross-loaded. We dug a couple of pits. The first, in Sage Basin was unremarkable. The second, at the edge of Sunlight Basin, yielded an ECTP23 on a layer of facets/ surface hoar buried two feet deep. 

We avoided wind-loaded slopes and recommend digging to test weak layers in the upper three feet of the snowpack before riding/ skiing in steep terrain. 

Riders north of Cooke City on 2/16/23 saw an avalanche that appeared to be recently snowmobile triggered.

Small storm slab released on a small piece of terrain. East aspect around 9200.

The Bozeman snow ranger crew rode on Buck Ridge today and did not see any recent avalanche activity.  There was 4-6 inches of new settled new snow over very firm older snow, so the riding was somewhat deceptive (not the easiest).  We rode out to Bear creek and the wilderness boundary there and noted that the new snow had been blown around quite a bit on the ridge tops.  Some folks had done some pretty aggressive riding in the upper portion of McAtee Basin but didnt trigger anything.  We also rode down Muddy Basin a ways and found much better riding there; less sled traffic and likely better wind shelter than buck ridge proper.  We peeked into the Yellow Mules and did not see any recent activity there, either.  Hope that info is helpful!

Low winds/no snow transport when I was up there and the east face had little to no wind effect, probably 16-18in new snow. Saw this slide with about a 8-12in crown and 100ft wide on the north face, didn’t see any other activity aside from some small point releases on really steep east aspects.

From another party: Saw a sizable avalanche on the north east face of Blackmore, likely broke mid storm and was partly filled in already - estimated 20" deep, 100' wide. Had shooting cracks and collapsing while ascending northeast ridge. Hand pits showed planar results on an 8" harder slab beneath all the blower on top. 

We toured up the Ramp near Bridger Bowl Ski Area today. On our tour up we saw a few small cracks in front of our skis in the new snow. Also, there were a few crowns and sluffs on higher peaks in the range. The wind blew from the W/SW throughout the day, and it was transporting the new storm snow into harder snow drifts. We dug a pit at 8,300' on a NE facing slope. The snow was 5 feet deep (HS = 150). The weak, sugary snow below the 8-10" of new snow were not reactive in our tests (ECTX 2x). The storm snow is becoming more stable as we move further from this storm. Now, the main concern is terrain with wind-drifted snow.