Snow Observations List

We were split boarding south of Cooke City today, up to terrain around 10'000', and finding good snow stability.

Weather was mostly cloudy in the am, partly cloudy in pm.  Light winds from the SW.

No fresh avalanche activity observed.  Attached is a photo of the only sign of a recent avalanche we could find.  (an old crown on an East aspect at 9600').

No collapsing no cracking.  

Storm snow:  was measuring the HN to be around 50cms at 8500', and 70+cms at 9500'.

With a snowpit attached from a E, NE aspect around 9500'.  CTN.

Wind effect:  significant in localized places, from the St. Patrick's Day event.  Wind drifts were not sensitive where we were traveling.

We skied north of Cooke today. The storm snow is upside down with a wind slab sitting on top. There is also a new dust layer that came in last night with the extreme winds. We had two collapses while skinning and ECTP13 down 60cm at the new/old interface on top of a crust, SE aspect at 9700'. Winds were L-M out of of the W and S2 snowfall all day with 8" new during the day.

Today I triggered a D1 dry loose avalanche on a E facing 35 degree slope, 9300 ft on Mt Henderson. The new snow is very low density and is not bonding well to the old interface. I also observed some more dry loose activity/small wind slabs on Sheep Mt, NE facing, 10400 ft.

Found 5-8” of fresh low-medium density snow. Triggered multiple small soft storm slabs/sluff which occurred on steeper slopes (40+ degrees). 
also noted an interesting crust overlaying a weaker layer that the new snow sat on. This crust wasn’t found everywhere, but just on the sides of rolls facing west or north west (between 9000’-9400’). When probed with a pole it sounded hollow. The crust was thick in nearly every place we found it and didn’t ever collapse under us, but it did shear in hand pits. A thin layer of graupel was also on top of this crust in some areas. 
other areas where this crust didn’t exist seemed to either not have refrozen completely before getting snowed on, or never got above freezing in the first place (high elevation north facing). In some areas the new snow bonded very well, in other areas it was easier to get it to sluff off the old crust. Attached is a quick photo of the crust location and the weak snow below it. 

Toured up the south end of Miller Ridge to 9,500'. Dug a pit on a northeast facing slope, 9300' (profile and pic attached). Snow depth was 7-8 feet.

6" of new snow was right side up. Below the new snow was a soft (1F-) melt-freeze crust with soft decomposing and slightly faceted particles below. ECTN13 broke below the crust. Below that the snowpack was 1F to P+ hard and lacked weak layers. The Feb 4 dirt layer was clearly visible.

There was a small natural dry loose on south face of Crown Butte and I triggered a dry loose slide on a test slope near the ridge (video). Wind was calm, even along the ridge near regularly wind-loaded slopes, and there was no snow blowing off ridgelines. I saw no signs of fresh wind-loading, but when the wind blows there will be fresh drifts that will be possible to trigger.

Skies were broken to partly sunny with a few light snow showers. Slopes that received sun got moist at the surface (at least below 9,000').

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.

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.

From obs: "We found up to a 6” deep wind slab producing shooting cracks at Goose Lake on a NW facing slope at 10500ft."

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.

No Recent avalanche activity observed in Hayden Creek or Republic Creek today with the the exception of some small dry loose in steep terrain. No Collapsing or Cracking during our day out today. 2" new at 8700' at 9am with another inch throughout the day. East winds were light throughout the day.

Observed some cracking in wind drifted snow above tree line NE facing slope. No avalanches observed 

Dug a pit at 9650ft on a 20° NE facing slope near Zimmer Creek. HS 210-230. ECTN14 at about 40cm down.  

Today we observed wet loose avalanches in steep, rocky terrain on the west side of Miller ridge. SW facing, 9500 ft

Snowpit attached from Mt. Republic today.  East aspect, 10,000'.

HS 165, ECTP22 at 65.  

No collapsing, no cracking, no avalanche activity to report.  

40 deg F at Fisher Creek SNOTEL today (9100').

Snowpit attached from an east aspect at 9400', south of Cooke City today.

HS 250 cms, with the Feb. 3rd dust layer about 100cms from the surface.  EXTX.

Below the dust layer there were 1mm rounding facets, that were 1F hard.

No avalanche activity observed, with LOTS of looking around.  No collapsing, no cracking.

Temps around 40F in the valley, but minimal wet loose activity observed so far.  The warmup has been gradual the last 2 days, with good freezes at night.

Also, there was a wolverine up on the mountain this morning!

Riding in this morning, we saw this older wet slide on the Portal Creek road down low at about 6400' in elevation on a south facing slope by lots of exposed rocks. For reference, Gallatin River is 5800' in this area.

We didn't see any fresh ones on our way out at about 2:30. 

The most likely places for big wet slides are slopes or areas with exposed rocks and cliffs. Generally these wet slides happen a little predictably in the afternoon as the snow gets wet. We know what time of day they'll happen, but it's hard to know exactly when they'll release, so watch out when the snow is obviously wet if traveling under slopes like this. 
 

You don't need to worry about them in the morning, when the snow is frozen. What a nasty avalanche with sticks, rocks, and dirt in it?

Fresh wind slab avalanche seen this afternoon, possibly rider triggered.

We received a call (from a third party) about a snowmobiler that was buried with their head 5 feet below the snow and their foot sticking out of the snow. Their partners saw the foot and dug them out. The riders face was blue, but quickly became responsive after a "chest thump". 

They were riding on the north side of Miller Mtn. Given the widespread winds and drifting, we suspect it was likely a wind slab avalanche similar to one spotted on Crown Butte the same day.

We went to look at an avalanche that was triggered two days ago, remotely from flat terrain above a steep slope, on the northeast end of Mt. Abundance. While looking for the avalanche from the flat bench above we triggered a similar sized slide directly adjacent to the previous slide. They broke on weak layers of facets and surface hoar that formed at the end of January. 2-3 feet deep and 150-200' wide. 1F to P- hard slab above the weak layer with 25cm of 4F to F snow at the surface. AFr-HS-R3-D2-O.

We also saw at least 3 rider triggered wind slabs, 4-5 natural wind slab avalanches, and a couple large cornice falls.

Strong wind had affected almost every piece of terrain, scouring some slopes, loading others, just stiffening the slab in many areas, and forming fresh drifts on every convex roll and along the edges of trails. Riding was still soft and fairly consistent in many areas.

I expect wind slab avalanches will be easy to trigger for a day or two more due to how reactive drifts were today... and it is still blowing and snowing a little more tonight.

The persistent slab avalanche problem is tricky because we have not seen any other avalanches of this type near Cooke City and it seems isolated, but slopes that harbor that instability might have just reached a tipping point with this round of wind-loading and dense snow, so it seems possible we could see a couple more of these avalanches over the next couple days or later this season. It will be a good idea to step back from most slopes steeper than 30 degrees during this wind-loading event, especially slopes with larger consequences like trees, cliffs and just generally large steep slopes.

Today I saw a very small wind slab on Republic Peak. Crown was 10 feet wide. No other avalanches observed