Slate River Crown Investigation 🕵️

CBACCBAC Observations

Date of Observation: 03/24/2023
Name: Evan Ross

Zone: Northwest Mountains
Route Description: Slate River. Variety of aspects. Mostly stayed within 500 hundred feet of the valley floor.

Observed avalanche activity: Yes
Avalanches: Many of the avalanches in the Slate and upper Slate have already been documented. I targeted specifics on those weak layers and that info is below. Avalanches on easterly aspects had the largest propagation and the most number of avalanches. However Northerly and westerly aspects had their share. The crowns in the alpine appear to be drifted back over or not visible with the recent weather.

I remotely triggered one large slab avalanche from a few hundred feet away, while traveling on a low-angled slope below. The avalanche ran on a west-facing aspect at 9,700ft. Later that day I found a D1 natural that ran today on another West aspect. These avalanches appeared to run on top of the 3/20 crust.

The NE to E Happy Chutes and Climax chutes had a handful of D1.5 to D2 slab avalanches from the last storm. The crowns were most commonly on the steep 40 to 40+ degree rollers in the terrain.

Weather: Calm to light wind in the valleys. Notable blowing snow off the high peaks in the later afternoon. Mostly cloudy and warm.

Snowpack: I targeted several old avalanche crowns to get a better sense of whether the recent avalanche cycle was breaking in non-persistent storm snow or the well-documented persistent weak layers in the upper snowpack. In each crown I checked out, the avalanche had broken on or below the 3/20 interface, before using the 3/15 interface as a bed surface.

On Easterly facing slopes, the 3/20 interface is a collapsible crust about 1cm to 3cm thick, and the avalanche activity on these aspects had propagated widely across the terrain. The 3/15 interface just made for a nice bed surface on all these avalanches. The crown heights were typically 45 to 65cm.

Where the 3/20 interface was NSF, on northerly facing slopes, the avalanches didn’t propagate as wide.

On westerly aspects, the upper snowpack structure is similar to that found on east aspects. I targeted one test pit on a west aspect 10,500ft, and got an ECTP 23 result on the 3/20 interface. Later I got the remotely triggered avalanche on another west aspect and saw the small nature on another west aspect.

I didn’t observe any obvious signs of instability. The upper slab has settled and gained strength.

Photos:

6156

Cement Mtn Slide

10webCBAC Observations

Date of Observation: 03/24/2023
Name: Cosmo Langsfeld

Zone: Southeast Mountains
Route Description: Cement Creek Rd

Observed avalanche activity: Yes
Avalanches: Fresh looking slide on Cement Mtn north bowl. NE-ish aspect, maybe some of the E facing terrain as well. Looks like it began in wind loaded terrain up high and stepped down into a deeper layer part way down the path. Spotted Friday morning.
Weather: Partly cloudy.
Snowpack:

Photos:

6155

Large Remote Trigger on Emmons

10webCBAC Observations

Date of Observation: 03/24/2023

Zone: Southeast Mountains
Route Description: Red Lady Glades

Observed avalanche activity: Yes
Avalanches: Remote triggered this repeat offender D2.5 from 50m away on ridge at about 12pm. Crown estimated to be 70m x 40cm. Failed at storm interface on 2mm facets resting on 2.5cm crust.
Weather: Sun, clouds & flurries. Light winds ATL.
Snowpack: Hand shear of crown “cash registered” as I was most of the way through cutting the block.

Photos:

6154

Ankle Biters in Cement Creek

10webCBAC Observations

Date of Observation: 03/23/2023
Name: Sam Strait

Zone: Southeast Mountains
Route Description: Snowmobile tour up Cement Creek Road and in terrain adjacent to road

Observed avalanche activity: Yes
Avalanches: 2x small (D1) naturals on W aspect @10,400

Weather: Mostly cloudy with brief periods of sun

6153

Upper Slate avalanche obs

CBACCBAC Observations

Date of Observation: 03/23/2023
Name: Eric Murrow

Zone: Northwest Mountains
Route Description: View from Elkton Knob.

Observed avalanche activity: Yes
Avalanches: Obvious natural cycle on Wednesday 3/22. Numerous avalanches broke near the storm interface on easterly aspects below treeline on Purple Ridge and Schuylkill Ridge near Pittsburg. Many of the easterly avalanches appeared to run late on 3/22. Looking at the up valley end of Schuylkill Ridge there was lots of evidence of avalanches running earlier in the storm but visibility was poor and I wouldn’t see crowns and debris was difficult to read. Atleast one avalanche near the last forested area before the Great Wide Open reportedly ran early Thursday morning. I never really got a good view of Scarp Ridge or the spine of the Ruby Range; I suspect there is more natural activity I was unable to see.
Weather: Mostly cloudy skies with periodic light snowfall obscured views.
Snowpack:

Photos:

6152

Naturals on Whetstone and Emmons

CBACCBAC Observations

Date of Observation: 03/23/2023
Name: Eric Murrow

Zone: Southeast Mountains
Route Description: HWY 135 observations.

Observed avalanche activity: Yes
Avalanches: A few more unreported slides on Whetstone and Mount Emmons that appear to break only in the recent storm snow.
Weather:
Snowpack:

Photos:

6151

Ruby natural avalanche – submitted via email

CBACCBAC Observations

Date of Observation: 03/23/2023
Name: Dave Kozlowski

Zone: Northwest Mountains
Route Description: Ruby Peak

Observed avalanche activity: Yes
Avalanches: natural avalanche on Ruby Peak.
Weather:
Snowpack:

Photos:

6150

Thick Storm Slabs

CBACCBAC Observations

Date of Observation: 03/23/2023
Name: Eric Murrow

Zone: Northwest Mountains
Route Description: Washington Gulch TH to Elkton Knob area.

Observed avalanche activity: Yes
Avalanches: I will put most avalanche coding and photos in another ob. No natural avalanche activity near TH. View from the top of Elkton Knob was marginal but buffed debris was visible (few crowns) all over the alpine terrain in the Northwest Mountains and covered many aspects; this drifted over natural activity involved storm snow only. Once on top of Elkton Knob there were a lot of widely-propagating crowns visible in the Upper Slate corridor near Pittsburg and on Purple Ridge below treeline. Easterly aspects seemed to be the bullseye below treeline. HIGH danger occurred at all elevations on Wednesday in the Northwest Mountains.
Weather: Mostly cloudy skies with periodic snow showers; no accumulations. Temperatures were seasonally cool, but solar radiation was enough to moisten snow surfaces on sunny aspects. Winds remained light with some moderate gusting up to 11,200. I saw a few periods of blowing snow across the highest terrain during the day. Settled storm totals up to 32″ at 11,000 feet.
Snowpack: The recent storm snow was thick and supportive to skis on all aspects with ski penetration around 7 to 10 inches. I experienced a few muffled collapses that did not travel far. Periodic sunshine moistened snow surfaces on E-S-W slopes below 11,000 feet but failed to warm enough to make loose avalanches an issue. Snowpack tests on easterly slopes produced moderate propagating results (see image) above the melt/freeze crust at the new/old interface. I traveled near several pieces of avalanche terrain trying to get a remote trigger without result; the storm slab is far too supportive and thick to consider ski cutting anything so I kept a safe distance from steep terrain. A profile on a northerly slope did not produce propagating results on the faceted new/old interface (1-1.5mm facets); I was fairly surprised by this given how weak this interface is.

Photos:

6149

Gothic 7am weather

CBACCBAC Observations

Date of Observation: 03/23/2023
Name: Billy Barr

Zone: Southeast Mountains
Route Description: Gothic Townsite

Observed avalanche activity: No
Avalanches:
Weather: Heavy snowfall Wednesday morning but only light in the afternoon and evening, stopping by midnight. The 24 hour total was 10″ new, with 0.88″ of water content. Wind became off and on, generally moderate with gusting but let up towards sunrise today. Snowpack reached 97″ deep- the deepest on record for March 22. Currently cloudy but calm and not snowing. The 24 hour high was 33 and the low and current 13. Snowpack dropped all the way down to 96½” (at this rate we should hit bare ground by October). billy
Snowpack:

6147

Naturals on Whetstone

10webCBAC Observations

Date of Observation: 03/23/2023

Zone: Southeast Mountains
Route Description: Observed from my kitchen window

Observed avalanche activity: Yes
Avalanches: Overnight natural avalanche cycle on E aspects of Whetstone.
Weather: Clearing skies
Snowpack:

Photos:

6146