We received reports of multiple natural avalanches following the strong southwesterly winds late Wednesday into early Thursday. There was some activity in the middle of our advisory area, with widespread activity on the south end of Turnagain Pass and Summit Lake.
Sunburst: A natural wind slab failed in the steep north-facing terrain off Sunburst ridge at around 2400′. The avalanche was around 2′ deep, 150′ wide, and ran an estimated 800′. More details here and here.
Seattle Ridge: We saw debris from multiple small natural wind slabs on the front side of Seattle Ridge, right across from the motorized lot.
Lynx Creek: There was a widespread cycle up Lynx Creek, with multiple natural wind slab avalanches around 2′ deep, over 500′ wide, running 1000′ vertical or more. Based on the depth of the avalanches and several snowpits we dug nearby, it is unlikely these failed on a persistent weak layer, but it is noteworthy how wide these avalanches propagated. Details here.
Summit Lake: Natural avalanches were reported on Fresno, Butch, Tri Tip, and Summit Peak. Many of these avalanches started as wind slabs around 1.5′-2.5′ deep, and stepped down to deeper weak layers surrounding the New Year’s and Halloween crusts. More photos here.
|Signal Word||Size (D scale)||Simple Descriptor|
|Small||1||Unlikely to bury a person|
|Large||2||Can bury a person|
|Very Large||3||Can destroy a house|
|Historic||4 & 5||Can destroy part or all of a village|
Winds have ramped up overnight after a brief lull in the action yesterday, with sustained speeds of 20-40 mph and gusts to 60 mph out of the east at the Sunburst station since 11 p.m. last night. With only a trace to 3″ snow overnight, wind slabs are once again the primary concern today. The strong winds are expected to slowly taper down during the day, but not before building a new round of sensitive wind slabs that will be easy to trigger. The size of the avalanches will be limited by the soft snow on the surface available for wind transport, which is unfortunately becoming harder to find. Don’t be fooled by the firm surfaces- the wind has a way of finding snow to move around, especially with another switch in direction yesterday. New wind slabs could be a foot deep or deeper, which is plenty deep enough to carry and bury a person. Be on the lookout for unstable snow near ridgelines, on convex rolls, and in steep gullies. These will be most likely in the alpine, but it will be possible to find reactive slabs near treeline as well.
In addition to the fresh slabs formed overnight, it may also be possible to trigger a stubborn wind slab avalanche on slopes that were loaded in the previous 48 hours. In some areas, downslope winds have loaded slopes farther down from ridgelines than we would typically expect (See Graham’s photo from the Skookum valley below for an example). This includes aprons below steeper terrain that we don’t always think of as dangerous avalanche terrain. This slightly more complicated distribution will require heightened awareness. Pay attention to clear signs of unstable snow like fresh avalanches, shooting cracks, and collapsing. Take the time to step off the skin track or hop off your machine and poke into the snow. If you notice stiffer wind-drifted snow on top of softer snow, stay off the steep slopes. Be aware that with the strong winds over the past two days, we could be dealing with a hard slab that will allow a person to venture out into the middle of a slope before triggering an avalanche. This makes it hard to avoid getting caught in a slide if things go wrong.
Cornices: As strong winds continue today, cornices are growing and will remain touchy. Be sure to maintain plenty of space from the edge, as these have a reputation of breaking back farther from the ridgeline than people expect.
More than just a little snow blowing off the top of Carpathian and Byron, above the Skookum glacier yesterday. Note the snow blowing downslope in the foreground, loading the lower elevation aprons at the same time the upper elevation start zones are being loaded. Photo: Graham Predeger. 02.10.2022
This is just one of many natural avalanches we saw in the Lynx Creek drainage yesterday. The snowpack seems to be more reactive towards the south end of Turnagain Pass, and especially touchy in the Summit Lake area. Dangerous conditions are expected to continue today. 02.10.2022
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Yesterday: A break in the weather yesterday brought partly sunny skies for most of the day, with increasing cloud cover in the afternoon. High temperatures were in the upper teens to low 20’s F, with the coldest temperatures in the morning in the single digits to mid teens F. Stations are showing a trace to 3″ snow overnight, with easterly winds increasing to 30-40 mph and gusts to 60 mph since 11 p.m. yesterday.
Today: Winds are expected to slowly taper during the day, dropping from 25-40 mph out of the east with gusts of 40-50 mph this morning to 10-20 mph by late afternoon. High temperatures will be in the low to upper 20’s F and may break in to the low 30’s F at sea level. We may see a trace of snow during the day, but clouds are expecting to break up again with some sun poking through.
Tomorrow: Clouds will roll in again later this afternoon into the early evening as another round of light precipitation brings another 2-3″ overnight. Winds are expected to stay light out of the southeast with lows in the low 20’s F. The snow line may creep up to 900′.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||20||1||0.1||91|
|Summit Lake (1400′)||20||1||0.1||37|
|Alyeska Mid (1700′)||19||3||0.2||91|
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||14||SE||12||25|
|05/11/22||Turnagain||Avalanche: Cornbiscuit and Magnum west faces||CNFAIC Staff Forecaster|
|05/07/22||Turnagain||Observation: Granddaddy||Kit Barton|
|04/29/22||Turnagain||Observation: Sunburst wx station||AS/ MM/ AM/ NH|
|04/28/22||Turnagain||Observation: More Turnagain Pass/Summit Lake wet slab activity||Alex Marienthal|
|04/27/22||Turnagain||Observation: Magnum||Sykes / Buttrick Forecaster|
|04/27/22||Turnagain||Observation: Girdwood/Summit/Turnagain Road obs||A S|
|04/24/22||Turnagain||Avalanche: Seattle Ridge – large glide avalanche on Repeat Offender path||CNFAIC Staff Forecaster|
|04/24/22||Turnagain||Avalanche: Seattle Ridge uptrack||Martin Schmidt|
|04/24/22||Turnagain||Observation: Pastoral||Jason Konigsberg|
|04/24/22||Turnagain||Observation: Sunburst||Lance breeding|
Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: email@example.com
|Area||Status||Weather & Riding Conditions|
This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.