Date of Observation: 12/11/2021
Name: Eric Murrow

Zone: Southeast Mountains
Route Description: Standard up-track on Snodgrass and ridge walk towards Third Bowl.

Observed avalanche activity: Yes
Avalanches: On the north side of Snodgrass, many steep, open features avalanched naturally during the storm. Some ran early with up to 16 inches of refill on bed surface and others failed late with 6 inches of refill.
Weather: Clear skies with cool temperatures and relatively light winds (I was below treeline for my tour, but did observe some drifting occurring above treeline on east, southeast, and south aspects)
Snowpack: On the north side of Snodgrass, snow depths were around 3 feet deep. Recent storm snow has settled to about 2 feet. Numerous muffled, small collapses while walking across low-angled slopes that had previously collapsed and shattered naturally during the storm. Several large, louder collapses while moving through low-angled northerly terrain without evidence of previous collapsing that traveled up to 100 feet. I dug one profile in a location with an intact snowpack and another on the bed surface of a natural avalanche that ran early in the storm. Northerly-facing slopes that have not avalanched remain very sensitive to the weight of a person.

Photos:

Date of Observation: 12/11/2021
Name: Evan Ross

Zone: Southeast Mountains
Route Description: Huge thanks to West Elk Air for getting the CBAC team views of the carnage. These photos are from Brush Creek area

Observed avalanche activity: Yes
Avalanches: The avalanche activity was much harder to see in the SE Mountains, compared to the NW Mountains. The avalanche activity in the SE Mountains was less widespread, smaller in size, and often hidden by wind-loading or additional snow after the storm.

The primary avalanche activity was on NE at all elevations. East, had activity at near and above treeline elevations and some suspicious-looking slopes below treeline but nothing that could be confirmed at that elevation.

South had activity above treeline, but again far less than the NW Mountains. I suspect that was to do with more south-facing slopes in this area having been dry before this storm.

West and North aspects were well shaded. If there was avalanche activity on those aspects, it couldn’t be confirmed on this flight.

Photos:

Date of Observation: 12/11/2021
Name: Evan Ross

Zone: Southeast Mountains
Route Description: Huge thanks to West Elk Air for getting the CBAC team views of the carnage. These photos are from the Mt. Emmons and Snodgrass area.

Observed avalanche activity: Yes
Avalanches: The avalanche activity was much harder to see in the SE Mountains, compared to the NW Mountains. The avalanche activity in the SE Mountains was less widespread, smaller in size, and often hidden by wind-loading or additional snow after the storm.

The primary avalanche activity was on NE at all elevations. East, had activity at near and above treeline elevations and some suspicious-looking slopes below treeline but nothing that could be confirmed at that elevation.

South had activity above treeline, but again far less than the NW Mountains. I suspect that was to do with more south-facing slopes in this area having been dry before this storm.

West and North aspects were well shaded. If there was avalanche activity on those aspects, it couldn’t be confirmed on this flight.
Weather:
Snowpack:

Date of Observation: 12/11/2021
Name: Ben Pritchett

Zone: Northwest Mountains
Route Description: Axtell as viewed from town

Observed avalanche activity: Yes
Avalanches: Couldn’t see 1st bowl well, but a few small ones below the skiers’ left cliffs. 2nd Bowl had broad-spanning soft slabs connecting the start zones a couple hundred feet below the ridgeline. Eraser and Pencil start zones both went, also well below ridgeline. That pocket feature between Wang Chung and 4th bowl went broadly. 4th bowl went R3, stopped just before the Shield. Green Lake Bowl from near the Eraser through the middle of the cliffs, looked early, kinda filled in. At least two of the Green Lake Chutes ran to the apron.

Date of Observation: 12/11/2021
Name: Zach Guy

Zone: Northwest Mountains
Route Description: Various from Axtell, Copper Creek, Peeler Basin, etc

Observed avalanche activity: Yes
Avalanches: See photos.

Date of Observation: 12/11/2021
Name: Zach Guy

Zone: Northwest Mountains
Route Description: Huge thanks to West Elk Air for getting the CBAC team views of the carnage.  These photos are from the Slate River Drainage from Purple Palace to Schuykill Ridge

Observed avalanche activity: Yes
Avalanches: Too many to count on the shady side of the basin. Lots of activity at all elevations, overlapping debris piles and evidence from early slide activity was obscured by subsequent snowfall. See photos.

Date of Observation: 12/11/2021
Name: Zach Guy

Zone: Northwest Mountains
Route Description: Huge thanks to West Elk Air for getting the CBAC team views of the carnage. These photos are from the Northern Ruby Range and Paradise Divide Area

Observed avalanche activity: Yes
Avalanches: Widespread activity on various aspects N and ATL near Paradise Divide. See photos.

Date of Observation: 12/11/2021
Name: Zach Guy

Zone: Northwest Mountains
Route Description: Huge thanks to West Elk Air for getting the CBAC team views of the carnage. These photos are from the Ruby Range.

Observed avalanche activity: Yes
Avalanches: Widespread large avalanches on most aspects above treeline. The most activity was on leeward aspects (NE, E, and SE).

Date of Observation: 12/10/2021
Name: Zach Guy

Zone: Northwest Mountains
Route Description: Lower Slate, Lower Oh-Be-Joyful. Traveled on NE, SE, and S aspects to 10,700 ft.

Observed avalanche activity: Yes
Avalanches: Nearly every northerly facing avalanche slope that we were close enough to have good views of slid naturally overnight. Where we traveled, most of the terrain was relatively small and slides were D1 to D1.5, one D2. It appears most of Climax Chutes also ran, generally D1.5 to D2.
Weather: Light snowfall through most of the day, with a couple of brief pulses of moderate snowfall. Gusty northwest winds in the afternoon were blowing snow at all elevations. Cold temps.
Snowpack: Widespread collapsing on northerly aspects; some muffled, some rumbling. Shooting cracks on many slopes. The only steep terrain that we felt comfortable traveling on, and without signs of instability, were recent bed surfaces, low elevation southerlies (which were previously bare and without fresh drifting), and dense trees. About 2 to 3 feet of storm snow.
Did this cycle flush the basal facets? In the bedsurfaces that we traveled on, there was a crust or roughed up stiff layer on the sliding interface, with more weak facets below. Enough to provide some structure for modest loading, but I don’t think we’re out of the woods because there are still weak layers hanging on. Time will tell, but I think this cycle only shaved off the top half of our weak layer where we traveled.

Date of Observation: 12/10/2021
Name: Eric Murrow Ben Pritchett

Zone: Northwest Mountains
Route Description: Kebler Pass

Observed avalanche activity: Yes
Avalanches: Observed one natural soft slab avalanche on a northwest-facing slope at 10,150′. Visibility was socked in, so very little opportunities to see recent avalanche activity.
Weather:

• Ridgeline Wind Speed: 20-30 mph
• Ridgeline Wind Direction: W
• Wind Loading: Moderate
• Temperature: 12 F
• Sky Cover: Obscured
• Depth of New Snow: 27 in
• Depth of Total Snow: 51 in
• Most Significant Precip Rate: S2 – 2 cm/hr
• Weather Description: One brief bit of broken skies around 10am, then it socked back in. Snowed S1-3 throughout the day without any breaks from 10am-3pm. Measured 51″ of storms snow which held 4.5″ snow water equivalent at Kebler Pass.

One brief bit of broken skies around 10am, then it socked back in. Snowed S1-3 throughout the day without any breaks from 10am-3pm. Measured 51″ of storms snow which held 4.5″ snow water equivalent at Kebler Pass.
Snowpack: Very deep, right-side-up storm resting on a very weak faceted base. Collapsing was rampant, but muffled. No cracking seen. ECT’s broke while isolating the block on size 10-15mm surface hoar, then gouged into facets.

Photos: