A skier or snowmachiner triggering a deep slab avalanche 2-4+ feet thick remains a very real and scary possibility. Strong Northwest winds over the last three days have been loading a variety of aspects and scouring ridge lines. This wind direction can funnel through Turnagain Pass and cause unusual loading patterns opposite of our normal Easterly storm tracks. If you’re out hunting for soft snow, be aware that dozens of large human triggered avalanches have occurred over the last 10 days across our region (Seward to Girdwood) including a large avalanche triggered remotely by a helicopter on Tuesday in Girdwood. Knowing where in the terrain a large and destructive avalanche could be triggered is a difficult question. It may be the 10th person onto the slope that finds a thin part of the snowpack (a trigger point) or it could be a person triggering a slab remotely on an adjacent slope or below. There is a lot of uncertainty around this avalanche problem due to well preserved and widespread buried surface hoar and facets under a thick, connected slab 2-4+ feet thick. This structure has been found at all elevations and on all aspects. Daily warming and radiation from the sun can make it easier to trigger in the afternoons and evenings, especially if winds are calm.
With a deep slab problem it is important to remember no signs of instability may be present before a slope releases. It is crucial to visualize the consequences if the slope does slide. Are there terrain traps below? Bigger slope = Bigger avalanche. Thin spots near rocks and along ridgelines are likely areas to find the trigger point.
A large avalanche was remotely triggered by a helicopter in Winner Creek near Girdwood on Tuesday. This avalanche was triggered from 1/4 of a mile away at 2500′ and released on the layer of weak faceted snow on a slick crust that has been the culprit in most of the avalanches over the past week.
A natural slab avalanche on a Northeast aspect of Raggedtop Peak in Girdwood at 3800′ was first seen on Tuesday morning, but it’s unknown when this avalanche released.
Wind Slabs: Be aware of newly formed wind slabs on a variety of aspects due to unusual wind loading patterns and cross loading from strong Northwest winds this week. Smooth supportable surfaces where the snow is hollow sounding are suspect, especially if the slope is unsupported. Look for cracking and identify terrain features with a pillow-shaped look where triggering a wind slab could break above you. Warming from the sun can make triggering easier in the afternoon, and a wind slab could step down to older snow and create a much deeper and more dangerous avalanche.
Cornices: Cornices are large and looming and the sun and above freezing temperatures can make them more unstable. Give these an extra wide berth and limit exposure underneath them. A cornice fall could trigger an avalanche on a slope below.
Strong NW winds moving snow around on Tincan Tuesday.
Yesterday strong NW winds 20-50mph (recorded on Seattle Ridge) continued for the third day in a row throughout our region and were more pronounced in Gap zones like Turnagain Arm. Overnight NW winds decreased to 10-20mph. Temperatures in the upper elevations were in the teens F and temperatures at sea level reached the upper 30F’s in the afternoon and dropped into the low 20F’s overnight. Skies were clear and no precipitation was recorded.
Today expect skies to remain clear and sunny. Northwest winds 10-20mph are expected to shift to the SE (5-20mph) by the afternoon. Daytime temperatures may reach the mid 30F’s in the upper elevations and low 40F’s at sea level. Overnight temperatures will drop back into the teens and low 20F’s.
Friday looks similar, but with calm winds and slightly warmer temperatures on tap. The next window for precipitation is Saturday afternoon and Sunday with scatter snow showers possible. Skies are expected to become overcast by Saturday afternoon with highs in the mid 30F’s and overnight lows in the low 20F’s. Easterly ridge top winds are expected to be light.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||24||0||0||81|
|Summit Lake (1400′)||22||0||0||32|
|Alyeska Mid (1700′)||22||0||0||76|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||19||NW||20||50|
|12/10/19||Turnagain||Avalanche: Tincan and Sunburst from the air||CNFAIC Staff|
|12/10/19||Turnagain||Observation: Tincan||Nancy Pfeiffer|
|12/08/19||Turnagain||Avalanche: Tincan||Ryan Van Luit Forecaster|
|12/06/19||Turnagain||Avalanche: Sunburst||Billy Finley|
|12/04/19||Turnagain||Observation: Sunburst||A.Johnston-Bloom/ W.Wagner/ R.Van Luit Forecaster|
|12/03/19||Turnagain||Observation: Hippy Bowl||Nick Langowski|
|12/01/19||Turnagain||Observation: Tincan, All elevations||Eric Roberts|
|12/01/19||Turnagain||Observation: Tincan||Andy Moderow|
|11/30/19||Turnagain||Observation: Tincan Treeline Plateau/ Common Bowl/ Ridge||Eric Roberts|
|11/29/19||Turnagain||Observation: Sunburst Ob #2||Aleph Johnston-Bloom Forecaster|
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|
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