Date of Observation: 12/16/2021
Name: Evan Ross & Alex Banas

Zone: Northwest Mountains
Route Description: Slate River. NE, 9,000ft to 11,400ft

Observed avalanche activity: Yes
Avalanches: Nothing fresh since last weeks avalanche cycle. Of particular note, during the 12/10 avalanche cycle an avalanche had propagated from Run Away Ski, through the Lap Track Track Trees, and through most of Yogies. In my 14 or so years in this area I’ve only seen an avalanche go wall to wall across the lap track trees a few times. Cool or not cool?
Weather: Clear sky, becoming partly cloudy. Moderate wind gusts at ridge line transporting snow.
Snowpack: The Slate River Valley had plenty of wind-affected snow, but as soon as we started climbing into the avalanche paths out of the valley the snow surface was all lovely and unaffected by the wind event. Snow surfaces were soft even at ridgeline elevations. Ski pen around 25 to 30cm.

The snowpack in this area was greatly affected by the avalanche activity between 12/9 and 12/10. There wasn’t a lot of undisturbed snow out there. In those undisturbed areas, the persistent slab avalanche problem felt stubborn. We were able to get a few collapses, often with some extra effort.

On the slopes that had avalanche a week ago, I was eager to see if they were developing a new avalanche problem. Below treeline, I didn’t find anything concerning. Near treeline, there were some areas that did pose a concern due to the additional wind-loading.

Below treeline, I didn’t find anywhere that enough snow has accumulated on those old bed surfaces to create a new slab on the remaining facets. The average new snow depths on top of those old bed surfaces ranged from 30cm to 90cm. From a distance, it’s difficult to identify the slopes that avalanched on 12/9, while the slope that avalanche on 12/10 remained obvious.

Near treeline, the slopes that avalanched on 12/10, or generally later in the storm, didn’t pose much concern for a new avalanche problem on this tour. The slopes that avalanched early in the storm, around 12/9, were harder to identity that they had previously avalanched. Those slopes had seen enough wind-loading over the last week to start creating new slabs right near ridgeline. In the end, we didn’t avoid wind-loaded terrain, be we did make assessments and encountered heightened avalanche concerns in those areas.

Date of Observation: 12/16/2021
Name: Zach Guy

Zone: Northwest Mountains
Route Description: Views of Scarp Ridge, some of the Ruby Range, Axtell, and Gothic

Observed avalanche activity: Yes
Avalanches: Not much interesting to report. Looks like a pair of slabs on a leeward aspect off of Scarp Ridge.
Weather: Cold and clear, no wind transport.
Snowpack: We were wondering whether the extreme alpine wind speeds were actively loading the alpine or just blowing into space. From my vantage, northeasterly aspects got fatter in the past 24 hours. Some terrain features on other aspects definitely got stripped.

Date of Observation: 12/15/2021
Name: Evan Ross

Zone: Southeast Mountains
Route Description: Gunsight Pass. Northerly facing slopes between 9,000ft and 10,400.

Observed avalanche activity: No
Weather: Felt like I was hanging out at an airport or something with jet engines running all day. The wind was generally light where I spent most of my day, but as soon as you get out of any cover it was full-on, strong down-valley winds. Lots of snow transport and wind erosion.
Snowpack: Around 10,000ft the HS averaged 70cm in the flats. Primary traveled on northerly facing slopes where it was easy to identify the layer of weak facets on the ground. Unforutnily they are just an arms reach way, or the layer is easy to identify with a ski pole. The mid-pack slab was around 4f hard over F hard facets The recent storm had deposited 3 to 4″ of new snow and the ski pen averaged around 25cm. In several places, there was small surface hoar just under the new snow, that somehow survived the early wind.

The persistent slab avalanche problem felt stubborn to trigger and lacked obvious signs of instability, without some extra effort. Usually, an extra couple of hard jumps could initiate a collapse where the snowpack had been undisturbed. The few bigger and steeper slopes I got close too, turned out to have already avalanched during last week’s cycle and had not yet accumulated enough new snow to become a problem again. From a distance, I wasn’t able to identify which slopes had or hadn’t previously avalanched.

Date of Observation: 12/15/2021
Name: Than Acuff

Zone: Northwest Mountains
Route Description: BTL, NE aspect

Observed avalanche activity: No
Avalanches: Only old ones
Weather: Low 20’s and snowy some periods of heavy snow. Winds pretty subdued aside from the occasional 15 mph gust which started from the SW on our way out but shifted to NW. Could hear it honking up high.
Snowpack: New snow overnight about 5″, 3″ fell while we were out there. Light and awesome. There was a crust on easterly aspects out in the open below the new snow.

Date of Observation: 12/15/2021
Name: Zach Guy

Zone: Southeast Mountains
Route Description: CB Nordic Hill

Observed avalanche activity: Yes
Avalanches: Ski cut a small wind slab, 10″ thick, on a small, windloaded slope below treeline.
Weather: Winds actively blowing a few inches of new snow.

Date of Observation: 12/15/2021
Name: billy barr

Zone: Southeast Mountains
Route Description: Gothic townsite

Weather: A lot of noise but little substance. The wind gradually built overnight to become a full on blizzard around 5 a.m. But by 7 the wind has let up and the snow has, for now, stopped. There was just 1″ wind blown and warm snow with 0.10″ of water. A good bit of wind transport but not a lot of new snow to move. Currently overcast with light SW wind and light snow seems to just be starting. Overnight high ws 30F after yesterday’s high of 38F. The current and the low is 18F with 18″ of snow on the ground as it continues to settle.

Date of Observation: 12/14/2021
Name: Eric Murrow

Zone: Southeast Mountains
Route Description: West Brush Creek road to skin up Union Chutes. Terrain south of WSC Peak in West Brush drainage, directly across valley from Teocalli.

Observed avalanche activity: Yes
Avalanches: Noticeably less avalanche activity below treeline as compared to Northwest Mountains forecast area. Near treeline produced numerous avalanches on north and northeast aspects directly below ridgeline in wind-drifted areas on shaded aspects.
Weather: Broken skies for much of the day with a pleasant period of Few clouds around 2 pm. Winds were light below treeline and looked to be moderate at ridgetop, but no wind loading was observed.
Snowpack: Small Surface Hoar was present near valley bottom but 100 feet above cold sink Surface Hoar disappeared. Snow surface on shaded aspects near and below treeline was faceted but small-grained (.5mm). Around 11,000 feet and above soft, breaker wind-board appeared across the landscape. I experienced many localized collapses, but just a single, loud moderately sized collapse as I exited a northeast-facing profile site (see attached image) which produced many cracks across the slope. I avoided steep, wind-drifted terrain in the area and stuck to simple, lower-angled options.

Snow depth on sunny slopes in the area was around 35cm and 70cm on shaded slopes. Ski penetration was generally around 6-8 inches and boot penetration was to the ground everywhere.

Photos:

Date of Observation: 12/13/2021
Name: Cormac Zachar

Zone: Southeast Mountains
Route Description: Skinned up the normal route via the woods to the south of the bowls. In the meadow approach, there were collapses and wumphing with almost every couple of steps. Several collapses propagated significant distances outward from the skin track. Once out of the flats, no obvious instabilities were present up to the ridge. Plenty of surface hoar everywhere the sun was hitting. Our skin track only crossed over 30 degrees once, and we didn’t test avy terrain on the descent either. Skied down the skiers left then right of second bowl… No signs of instability while skiing, but only crossed over 30 degrees once and for no more than a hundred feet.

Observed avalanche activity: Yes
Avalanches: No new slides. Skinned past the previously reported skier-triggered avalanche in Convex Corner. Appeared to have a 2-3 ft deep crown and ran approx. 75 yards (D1.5?). Avy path was almost identical to the area of transition between <30 and 30-35 degree slopes on the upper third of Convex.
Weather: Sunny, low 30s.
Snowpack:

Date of Observation: 12/13/2021
Name: Alan Bernholtz

Zone: Northwest Mountains
Route Description: Poverty Gulch area. This observation confirms the forecast from this morning.

Observed avalanche activity: No
Avalanches: Several old avalanches were observed. Some ran during the storm and some ran at the end of the storm. All were old.
Many cracks were observed on steeper slopes as well as low angle. We only heard one collapse during our hike.
Weather: Mostly clear, a few high clouds, strong solar radiation, no wind and estimated temp around 35
Snowpack: At the top of the skin track we found 100cm HS. 70 cm HST, 4-5 cm of sun or temp crust and 25 cm of facets. Surface hoar covered all aspects.

Date of Observation: 12/13/2021
Name: Zach Guy

Zone: Northwest Mountains
Route Description: Various aspects near Kebler Pass and Lake Irwin.

Observed avalanche activity: Yes
Avalanches: Nothing new. Documented a few older slides from the past cycle.
Weather: Few clouds. Moderate southwest winds at ridgetop with some light transport at times.
Snowpack: Primary goal today was to test the sensitivity of the persistent slab problem on shady aspects. Although it’s getting harder to produce signs of instability than earlier this week, the snowpack is still talking. I skinned over, then jumped with skis on, and then post-holed into four suspect low-angle slopes below treeline. One slope remained quiet, one produced a localized collapse when I skinned over a shallow, wind eroded feature, and two of them produced rumbling collapses after I stepped out of skis and sunk my boot into the weak layer. Slab depths in this area were 75 to 80 cm to the 12/6 facet layer.
Also dug into a southerly aspect near treeline to test bonding to the 12/6 crust. No alarming results and no signs of instability while traveling on southerly aspects.

Surface hoar growth observed below treeline.