The weekly summary is here. A 20+ inch storm of heavier-than-average snow on Wednesday 12/27 brought winter back to the valley and High avalanche danger. More snow is on the way for this weekend and the avalanche danger will rise accordingly.
Weekly Summary December 23-29 updated-compressed
Date of Observation: 12/29/2022
Name: Eric Murrow
Zone: Northwest Mountains
Route Description: Washington Gulch to Elkton Knob area.
Observed avalanche activity: Yes
Avalanches: Visibility was obscured all day, but I did get a view of two natural avalanches off Gothic Mountain. One was reported In Zach ob earlier today. The other was on a near treeline southwest-facing slope; it appeared to break only in the recent storm snow based on depth, D1.5 best guess.
Weather: Mostly cloudy skies, with very light but consistent snowfall through 3pm. Total storm depth through 3pm at 11,000 feet near Elkton was about 22 inches. Westerly winds blew at light speeds with moderate gusts throughout the day. Some snow transport near treeline and modest loading above treeline.
Snowpack: I traveled mostly through near treeline terrain. I experienced no signs of instability underfoot other than some ski-length cracks on drifted easterly terrain. I did not observe any buried surface hoar. The new snow remains dense but relatively soft. In this near treeline terrain, the 12/20 facet layer is capped by a thin windboard from last week’s wind event. A test profile produced no propagating results (see photo). Basal depth hoar remains in the Fist plus or 4 finger minus hardness range. This storm appeared to not quite be enough load to cause widespread natural activity for the ‘snowbelt’ region but, as mentioned above, visibility was obscured.
Date of Observation: 12/29/2022
Name: Zach Kinler
Zone: Southeast Mountains
Route Description: Standard Red Lady skinner to the glades.
Observed avalanche activity: Yes
Avalanches: Saw 2 naturals on a SE aspect around 11,200′ that failed late yesterday with several inches of snow in the bed surfaces. Both released on surface/hoar resting on a thin melt-freeze crust. D1-D1.5 in size. Crowns were around 10″.
Weather: Cloudy and cold, westerly winds were light in lower elevation sheltered terrain but moderate near and above treeline.
Snowpack: Fairly quiet snowpack when departing the skin track and on the descent. The recent collapses have been very quiet so possibly didn’t hear some of them. There was around 12″ of recent snowfall on the 12/27 interface. On south and southeast aspects this layer was surface hoar resting on a 2-3 cm crust. SH did not look as large or well-developed as other slopes I have seen. Looks to be decomposing a bit and getting entrained in the slab. It still produced easy hand sheers and is weak. Stomping on a few east and southeast slopes from the ridge did not produce any results.
Date of Observation: 12/29/2022
Name: Zach Guy
Zone: Southeast Mountains
Route Description: Rec tour on Anthracite Mesa, traveling on various aspects to 10,800′
Observed avalanche activity: Yes
Avalanches: Large natural slab avalanche likely ran this morning on a southwest facing slope of Gothic, to the ground. Skier triggered a couple of thin soft slabs that failed within the storm snow on lightly cross-drifted southerly terrain. Had decent vis of the Lower Slate from Birthday Bowl on Skooks to Happy Chutes and only saw a handful of loose dry avalanches.
Weather: Very light snowfall. Light winds with occasional moderate gusts causing brief periods of blowing snow. Cold temps.
Snowpack: 35 to 40 cm of F to F+ snow down to our most recent facet (1mm) and crust/facet layers. This interface produced only minor cracking and non-propagating results in quick tests. No signs of buried surface hoar here. In lightly wind-drifted terrain exposed to down valley winds, we produced shooting cracks and triggered a couple of soft slabs breaking on precip particles within the storm snow, up to 25 cm thick or so. One was remotely triggered from 20 meters away.
Date of Observation: 12/29/2022
Name: Billy Barr
Zone: Southeast Mountains
Route Description: Gothic Townsite
Observed avalanche activity: No
Weather: Light snow during the day with 4″ new and 0.24 SWE, then snow last night ending by midnight with 3″ more and water 0.21″ so the 24 hour total was 7″ new and 0.45″ of water content. It remained cloudy and calm while warming to freezing and then cooling to 11F overnight. Currently overcast and not snowing with a light westerly wind and 13º with a light wind. Snowpack is at 37″. billy
Date of Observation: 12/28/2022
Name: Eric Murrow Zach Kinler
Zone: Northwest Mountains
Route Description: Kebler Pass to Anthracites standard skin track.
Observed avalanche activity: Yes
Avalanches: No natural avalanches. Observed two small human-triggered avalanches by other parties on east and northeast aspects. We remotely triggered 3 separate avalanches, D1 and D1.5, on northeast, southeast, and south aspects. All of the avalanches we triggered failed on Surface Hoar immediately beneath the storm snow.
Weather: Mostly cloudy skies with light snowfall throughout the day. The height of storm snow at 2pm was about 13 inches with 1.3″ of water. Winds remained light at the ridgetop with no drifting observed.
Snowpack: In each place we looked, northeast through east through southeast through south near and below treeline, we found 6 – 9 mm surface hoar beneath the storm snow. The collapses that triggered the avalanches mentioned were quiet and hard to hear or notice. One of the avalanches on a southeast aspect was triggered from 150 feet away. Whether the weak layer was buried surface hoar, the 12/20 facets, or within the storm snow, it seemed likely to trigger a small avalanche in the surface snow (some long slopes could have approached D2 size). On southerly slopes, a melt-freeze crust formed in the past few days that have the potential to collapse and produce avalanches with more snowfall this weekend. Below the crusts, the snowpack was only lightly faceted but remains soft and collapsable. The biggest takeaway was buried surface hoar, in open areas, beneath the recent storm snow on most aspects near and below treeline in this area.
Date of Observation: 12/28/2022
Name: billy barr
Zone: Southeast Mountains
Route Description: Gothic
Weather: Obscured with moderate to heavy snow since starting 12 hours ago with 9½” new and water content 0.82″ and no wind (hooray for that). It stayed very warm last night with the morning low the current 27F after a high yesterday of 41F. Currently snowing moderately with no wind and no visibility. Snowpack is at winters deepest of 31½”. There was a bit of crusting on southern slopes yesterday but now buried.
CBAC will be at the Snodgrass Trailhead this Saturday, December 31st. We are sending out 2022 with a bang as the Atmospheric River has returned! Come out for the latest avalanche conditions, friendly banter, maps, stickers, snacks, music and more.
Date of Observation: 12/27/2022
Name: Zach Kinler and Evan Ross
Zone: Southeast Mountains
Route Description: West Brush Creek
Observed avalanche activity: No
Avalanches: A couple of very small facet sluffs on steep, sheltered East aspects.
Weather: Cool and moist in the valley to start the day with clouds thickening. Nice and warm once we were out of the inversion, light southerly winds in open areas.
Snowpack: We traveled on east and southeast slopes from 9,800′-11,400′. The upper half of the snowpack in this zone is very weak. Southeast slopes had an HS of 50cm. Surfaces were a 3cm crust followed by 10cm of moist rounds. Below that was a thin crust with facets above and below. The bottom 30cm were moist grains to the ground. Moving into east, HS was 60cm, the surface crust was not present just 30cm of fist hard large-grain facets above a 4F faceting slab. 3-4 mm Surface Hoar was present from valley bottom to over 11,000ft on east aspects.
Date of Observation: 12/26/2022
Name: Evan Ross
Zone: Northwest Mountains
Route Description: Primarily SE to SW between 10,000ft and 11,000ft.
Observed avalanche activity: No
Weather: Few clouds in the morning becoming overcast in the afternoon. Calm wind.
Snowpack: Targeted three test profiles, specifically looking at the upper snowpack, on SE, S and SW. The two most prominent interfaces are in the upper 15 to 35cm’s of the snowpack, depending on location, (12/11 and 12/20). On the south and southeast, the grains at those interfaces are around 1mm in size and notably rounding. The rest of the mid and upper snowpack at these locations had little change in hardness and looked generally strong, at least compared to current big-picture conditions. In the SW profile, the HS was notably less, and those two interfaces had slightly smaller grains, but they remained faceted and were not rounding.
Aspect: SE. Elev: 11,250. Slope: 30. HS: 103. 12/20 interface down 15cm and 12/11 interface down 25cm. 1mm rounding faceted particles at both interfaces. Some necking between grains. CTM, ECTN 15.
Aspect: S. Elev: 10,850. Slope: 30. HS: 128. Cross-loaded slope. The two interfaces were down 25cm and 30cm. Similar grains to the SE aspect. ECT PC 17, interestingly two additional loading steps were required to get the fracture to cross the column. Followed by an ECTN with no propagation across the column.
Aspect: SW. Elev: 10,800. Slope: 33. HS: 70cm. The two upper interfaces were down 15cm and 20cm. The most notable had a 1cm soft crust capping 1mm facets. Given the shallower snowpack compared to the other two locations, this snowpack was noticeably weaker and will handle less loading once a new slab develops.
Photos:
