We received multiple reports of cornice falls being triggered yesterday. One was triggered by two snowmachiners walking out too far onto the Warm-up Bowl corniced ridge. From what we know one person went down with the cornice chunks but was ok. Another cornice fall was triggered skinning along the Tincan ridge towards Tincan Proper and one was dog triggered along the Sunburst ridge. Luckily no one was injured in these and the cornice falls did not trigger avalanches on the slopes below. Remember to give cornices a wide berth on the ridge as they can break off further back than expected and potentially take you for a nasty ride. They could also trigger a wind slab or larger avalanche below, creating an even bigger problem. It is also important to limit exposure time below them especially with so many people out enjoying the snow this holiday week.
WIND SLABS: Saturday’s sustained NE winds that were strong enough to move snow around and form cornices also potentially created wind slabs on steep, unsupported slopes. There were reports of observers yesterday finding small pockets of wind slab. Continue to be on the lookout for these today. At this point they may be stubborn and could allow a person well out onto them before releasing. Watch for shooting cracks, hollow sounding snow and be especially aware of the terrain – if a wind slab or cornice does release where will you go?
Cornice fall triggered skinning along Tincan Ridge towards Tican Proper, 12-23-18. Photos: Owen Smith
Cornice diagram from the Avalanche.org encyclopedia. Note the potential fracture zone on the ridge.
Buried weak layers roughly 2′ below the snow surface have been found in areas south of Turnagain Pass in both the Summit Lake zone and as far south as Lost Lake. We suspect the snowpack may be similar around Johnson Pass, Lynx drainage and Twin Peaks/Silver Tip. These weak layers are composed of facets associated with crusts and have been showing signs they could be reactive enough a person could trigger a large avalanche. If you are headed to areas south of Turnagain, keep in mind triggering a large slab avalanche is possible. Listen and feel for whumpfing (collapsing of the snowpack) and look for avalanche activity from the storm that may have steeped down into the deeper layers.
Slab avalanches just south of Turnagain Pass that occurred during the Solstice Sleeper Storm believed to have released on the crust/facet set-up. 12-20-18
Watch for opening glide cracks. These are likely to be oozing down the slopes with all the new snow weighing the snowpack down. Glide avalanches can release at any time and are not associated with human triggers. It’s a case of not wanting to be in the wrong place at the wrong time. There are glide cracks are opening up on the SW faces of Tincan and Sunburst as well as the Johnson Pass area and Gold Pan in upper Bertha Creek.
Glide cracks and cornices in Gold Pan, 12-23-18. Photo: Peter Biskind.
Yesterday: Skies were clear with some valley fog. Temperatures were in the 20Fs and winds were light. Overnight temperatures were in the teens and low 20Fs. Winds remained light.
Today: Skies will be partly sunny with temperatures staying in the teens to low 20Fs and winds continue to be light. Temperatures drop into the low teens overnight.
Tomorrow: Skies will be cloudy, temperatures will be in the high 20Fs and there is a chance of Christmas snow showers as a front moves into the area. We are paying attention to the next series of lows developing that may impact the region later in the week! Stay tuned.
*Seattle Ridge weather station is rimed over and not recording any data.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||24||0||0||61|
|Summit Lake (1400′)||18||0||0||
|Alyeska Mid (1700′)||24||0||0||33|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||*N/A||*N/A||*N/A||*N/A|