Snow Observations List
Today I observed multiple small wind slab avalanches off Woody Ridge. NE and E facing, 10000 ft. Max size D1. Also, there was many dry loose slides on Cooke Peak in Hayden Creek.
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We rode to the top of Sawtelle to de-rime the anemometer (wind sensor) and then down into Rock Creek Basin under all the big north facing avalanche paths.
Key findings:
- New snow amounts ranged from 6-8" at lower elevations and 18" at higher elevations
- We did not observe any cracking or collapsing on non wind loaded slopes.
- We observed two very recent natural storm slab avalanches about a 1.5 feet deep. One of them entrained a significant amount of snow an ran a long ways.
- There has been minimal wind effect except at ridgetops
- Extended Column tests on north facing slopes continuously broke and propagated after 12 taps (ECTP12) just under a soft crust in snow that fell last weekend. These appeared to be breaking on broken stellars/snowflakes. On other aspects, the crust was much thicker and harder.
Conclusions:
The likelihood of triggering a soft slab avalanche about 1.5' deep seemed low on non-wind loaded slopes. Any amount of wind affecting a slope whether loading a slope or just stiffening the new snow, dramatically increased the odds of triggering a slide. We felt comfortable riding in avalanche runout zones and even climbing into the paths some. The main strategy was to stay out of the upper starting zones that are steeper and have seen some wind. HOWEVER - we carefully limited our exposure in big runout zones where a falling cornice could have triggered a slide that could have crashed down onto us. We did not think that we would trigger an avalanche from below
Looking ahead - Strong winds Sunday through Monday will have plenty of snow to transport along with additional snow that will fall. This should increase the danger and the size of possible avalanches.
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From phone call:
Kevin took a group into the Centennials.
8" of new snow at 8000'. Surface crust below the new snow was 3 CM thick. There was a facet layer below crust that was concerning. ECTN3 below crust.
Kevin found the January facet layer 90 CM down (4F hardness) a couple miles north of White Elephant at 7800-7900' (0.5-1mm size). No results in tests but was concerned about their activation if the storm snow start stacking up.
He noted that the Wind Slab and Storm Slab problems are growing. He saw shooting cracks in the new snow, several feet in front of his skis.
Winds were light to moderate but gusting into the 20s mph.
Full Snow Observation ReportWent up to Beehive Basin to check out the new snow as it was falling ---- but it wasn't, yet (between 10 am and 1 pm). There was a dusting of new snow when we arrived at the trailhead and a few flakes fell during the couple hours we were up there, but the substantial accumulations hadn't started. In fact, skies were mostly clear during our tour.
We skinned up the west facing sub-ridge to the Prayer Flags and descended via the Going Home Chute. Surface conditions were rough on any slope that wasn't shaded, with stout melt-freeze crusts. There was still a tiny bit of old, soft snow present in the shade.
No signs of instability or recent slab avalanches noted (we did see some older, wet loose slides).
Danger was LOW, while waiting for the storm to start in earnest.
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The winds were strong enough combined with the higher humidity snow that pinwheels were actively forming and moving on flat to slightly downhill terrain. I hadn’t seen this often, so I thought it was worth sharing.
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Toured into Texas Meadows this morning. No avalanche activity seen, no cracking or collapsing. Northern aspects and higher elevations holding better snow, without a wind or sun crust.
Full Snow Observation ReportRode into Fairy Lake and skinned up the east shoulder of Naya Nuki. Winds went from strong to extreme out of the south in the early afternoon and were absolutely hammering. Despite the crazy winds, there was really no snow left to transport, so there was no active windloading. Wind surfaces were highly variable, from sastrugi to windboard to meltfreeze crusts to protected powder in the trees.
Saw no signs of instability or recent slab avalanches. We did see a good bit of wet loose activity that likely happened a couple days ago.
Full Snow Observation ReportLOW danger is right.
Toured onto the west side into Jones Creek and then down Wolverine Bowl. Found lots of crusty snow, wind scoured snow, hard wind drifts, and even some warm, dry powder. No near surface facets which is a good thing for future stabilty.
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We rode from the Sawtelle Parking area up the shoulder of Sawtelle, across Yale Creek and above East Hotel Creek, through Jefferson Bowl, into Hellroaring Creek drainage to the base of Reas before reversing the order and heading out. We saw no avalanches and no signs of instability. Three snowpits (above East Hotel, in Jefferson Bowl, and above Hellroaring) revealed nothing remarkable - ECTXs and ECTNs in the 20s. The south-facing pit above East Hotel had many crust facet sandwiches, but none are currently an issue. It would take a significant load to bring up any concerns about avalanches breaking on persistent weak layers deeper in the storm.
Stability is good. There are tracks everywhere, and we are looking forward to a reset, hopefully arriving Wednesday night. Most slopes have a melt-freeze crust at the surface. There is no remarkable weakening at the surface to note at this point. Unless something changes between now and Wednesday, instability should be limited to the incoming snow and wind-drifted snow.
Full Snow Observation ReportDanger was LOW.
We rode out Lionhead Ridge and around the north end to the head of Targhee Creek. Skies started overcast, but cleared through the day as wind calmed from moderate to light out of the west and southwest.
There were zero recent large persistent slab avalanches, and there were two or three shallow small wind slabs below Lionhead Ridge. The snow surface became moist, but crusts from previous warm days and cold night only softened slightly. There was very little, if any, wet snow avalanche hazard today.
We dug at the top of Lionhead Ridge on the south side of Airplane Bowl. 9,300', NE aspect. There was a 2.5' deep very hard slab (1f to P+) above soft facets (4F-), snow depth of 5 feet. We had ECTX, but with extra hits and some removal of the slab it propagated with a clean break. The persistent slab avalanche problem is becoming more stubborn, but not going away. For now it is not likely, but there is probably an isolated slope where you could trigger an avalanche, and we could see this problem arise again with more snow next week.
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We skied to Flanders Mountain, traversed the ridgeline, and dropped into the northwest-facing terrain near the Winter Dance Buttress down to the Main Fork. Ridgelines had moderate to strong winds but minimal transport as snow at upper elevations had already moved or had hardened with recent wind and warm temperatures. Wind Slabs that we assessed were stubborn to unreactive, but there is probably one out there that could result in a small avalanche. No signs of dry snow instability during the tour or in our snowpack assessments (Flanders Bowl - ECTN Teens and 20s and Near Winter Dance Buttress - ECTN Teens and 20s). Snow surfaces were warming (wetting) in south-facing terrain and on all aspects below 8000' by 3 PM. However, we did not see any natural wet snow activity.
I would be watching out for isolated wind slab instability and wet loose avalanches for now.
Full Snow Observation ReportLOW Danger.
Somewhat fresh looking slab avalanche in upper Storm Castle Creek on an East facing slope. Looks like there might be a wet loose slide to the right of it as well. One small wet loose avalanche, probably from yesterday, in Maid of the Mist bowl.
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Expected to find a different snowpack in the area southwest of Cooke/Silvergate, but once again we found deep (HS 235cm), strong, stable snow.
Digging more than a foot or two into the snowpack is a chore. Even the north-facing snow below 8000' is incredibly dense and supportive.
It seems like recent warm weather really helped consolidate the snowpack.
Don't take this good stability for granted - Even though the snowpack is generally stable, there is still trouble to be found in more consequential terrain. In one area, we did find some upside-down snow. It seemed stable, but in very steep terrain, even a small pocket releasing can cause trouble. We also witnessed a falling cornice today that washed some snow through rocks. Be aware of what's above you.
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From obs: "We found up to a 6” deep wind slab producing shooting cracks at Goose Lake on a NW facing slope at 10500ft."
Full Snow Observation ReportToured into Ainger Lake Basin in the Northern Bridgers today. From the Shafthouse Trailhead we could see debris from past wet snow avalanches coming from Ainger Peak and Hard Scrabble Peak area. The slide in Ainger Lake Basin must have been at least a few days old as the slide path and debris were covered in new snow from the last snowfall. The evidence of multiple slides we saw in Ainger Basin looked like they came from rocks shedding snow in the warm weather we've been having. Our objective was the middle couloir on Ainger Headwall. It was very windy in the basin. The slope above Ainger Lake Basin that we had to cross to get to the couloir was heavily wind loaded. We toured up and the snow felt stable so I decided to slowly skin out to see how the snow on this slope felt. It quickly became hollow sounding and we turned around and got a couple laps in for the day from there. Up high in the basin sun baked slopes that froze over night were very slick and hard with a couple inches of new snow on top making skinning difficult in places as well.
Full Snow Observation ReportWidespread wind effect in the alpine of Hyalite yesterday. The windslabs were fairly stubborn however, and were only breaking in very small pockets, not propagating outwards. Where the recent snow was still protected from sun and wind, large dry loose slides were easy to trigger.
Full Snow Observation ReportWe rode from Battle Ridge and skied up the east face of The Throne to look at the stability of the recent new snow.
There was 6" of low density snow from yesterday. Winds were stronger than expected, from the north at the top of the Throne, and increased through the morning.
We found fresh drifts that were reactive, cracking easily and 5-10' wide out from our skis, on south and east facing slopes around 8000-8300'.
The new snow was low density and sluffed easily on steep shady northerlies. On steep slopes facing the sun (south and east, and probably west) the new snow sat on a crust and became moist as the sun warmed it up and started to slide under skis. We saw a couple very small natural loose snow slides below rock outcrops on south facing slopes. Air temperatures were well below freezing, especially with wind chill, but the sun quickly warmed the recent new snow.
It is spring, in addition to assessing for unstable drifts of snow, plan for wet snow avalanche hazards to increase in likelihood throughout the day when the sun is out and temperatures are near or above freezing.
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Rode to the wilderness boundary and skied a lap above Goose Lake. Dug in two places - all hard, dense, strong, deep snow
Rode above Goose Creek. Dug in two places along the very steep, north-facing slopes above the creek. Same. All hard, dense, strong, and deep snow. Facets from late January are buried about a meter deep and 1Finger+ hardness.
We were digging about 700 feet above the two persistent slab that were avalanches triggered on Feb 24th (about a week and a half ago). We didn't see any indication that that is a widespread problem. We didn't see any recent avalanches either.
Digging down to the late-January facets was a pain in the a$%. It seems like when it's becoming a pain to dig down to a weak layer, it's usually not much of problem anymore.
Full Snow Observation ReportDanger seems LOW
Looks like a recent naturally triggered slide towards the Idaho wilderness boundary on lionhead.
GNFAC note: This slide occurred on Feb 28th (previous observation)
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