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The avalanche danger is CONSIDERABLE in the Alpine and MODERATE below. A very cautious mindset is required for travel in exposed areas above the trees today as large and dangerous slab avalanches may still be likely to trigger on steep slopes. These slabs are 2-4+feet thick and sitting on weak faceted snow. Lingering wind slabs, around a foot thick, and sluffs will be possible to trigger. These smaller slides could initiate a larger slab on steep terrain.
Travel Advice | Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. | Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. | Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. | Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. | Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain. |
Likelihood of Avalanches | Natural and human-triggered avalanches unlikely. | Natural avalanches unlikely; human-triggered avalanches possible. | Natural avalanches possible; human-triggered avalanches likely. | Natural avalanches likely; human-triggered avalanches very likely. | Natural and human-triggered avalanches certain. |
Avalanche Size and Distribution | Small avalanches in isolated areas or extreme terrain. | Small avalanches in specific areas; or large avalanches in isolated areas. | Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. | Large avalanches in many areas; or very large avalanches in specific areas. | Very large avalanches in many areas. |
The skies cleared just enough yesterday afternoon to get a look at some of the natural avalanche activity that occurred during the storm Wednesday night, just 36 hours or so ago. Several wind slabs released, around a foot thick, that were partially filled back in. The more concerning avalanches however, were several slabs that appeared to have released in deeper buried layers, around 2 feet thick. These were observed on Sunburst, Tincan and Magnum and are pictured below.
Sunburst’s lower north ridge. If you look close you can see the partially filled in ~2 foot crown just off the ridge and extending for several hundred feet. This character of this slab points to failure in a buried weak layer as opposed to simple wind loading.
Magnum’s west face. Despite many sluffs and shallow wind slabs on this face, the spooky avalanche is the one at the top, the pocket that pulled out just under the rocks. This slab is near the slide that was human triggered in weak faceted snow around 3 weeks ago and like Sunburst, is indicative of failure in older weak snow.
This slab, who’s crown is partially filled in by wind, is also suspect for failing in buried weak snow. Located on the north side of Tincan Ridge, the Tincan north chutes, and just over the ridge from Hippy Bowl.
Slab avalanche seen on the Penguin Ridge, SE facing in Girdwood Valley yesterday as well. This slab also has the character of releasing in older weak snow. 1.30.20. Photo: Mike Welch
A typical wind slab, around a foot deep, that released on Tincan’s CRF ridgeline, SW aspect.
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 |
Skies are dawning cloudy this morning, winds are light and temperatures are in the single digits. For those of you headed out and hoping the skies open enough for travel above treeline- BEWARE. There is a lot of uncertainty as to how tenuous the snowpack is right now.
Sitting under all the low-density snow from the last half of January (2-4+ feet of soft powder snow), are weak sugary facets and buried surface hoar. The winds from Wednesday night not only affected the surface snow, but they also tipped the balance just enough to initiate some natural avalanches. Some were in the form of common wind slabs, but what is much more concerning, were the slabs that are suspected to have released in deeper layers in the snowpack. Although the natural avalanche cycle was not widespread, that also means many slopes could still be hanging in the balance, just waiting for a trigger.
Very conservative terrain choices are advised today as the snowpack adjusts. It is just 1.5 days after the end of the natural cycle and although the likelihood of triggering a large slab should be decreasing, patience is key. Things to keep in mind if travel is possible to the higher slopes:
One of many snow stability tests performed on Tincan yesterday. Results were varied and pointed to areas where the buried weak layers were showing signs of reacting and areas they were not.
Video link 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 |
Lingering wind slabs from the strong winds Wednesday night may still be possible to trigger on steep slopes. These are expected to be around a foot thick and somewhat stubborn. The more concerning issue is if a small wind slab triggers a deeper weak layer and a larger slab avalanche occurs. This can make for a very unmanageable and dangerous situation.
Loose Snow Sluffs: Expect sluffs on steep slopes in areas that were spared the winds. In the lower elevations, these sluffs could entrain a large amount of older storm snow and be larger than expected.
Yesterday: Mostly cloudy skies with light snowfall was seen yesterday morning before skies broke and the sun shown through during the afternoon. Up to an inch of snow fell during the morning hours in most locations with 3-4 inches in Portage Valley. Ridgetop winds were light from the east. Temperatures were in the single digits in the Alpine and in the teens at the lower elevations.
Today: Mostly cloudy skies with a few snow flurries are expected today. Ridgetop winds are light and have just turned northwesterly this morning, where they should remain in the 5-10mph range. Temperatures cooled in valley bottoms overnight and are expected to reach into the single digits today. Upper elevation temperatures should remain in the single digits.
Tomorrow: Mostly clear skies and cold temperatures are in the forecast for Saturday- BUT models are showing the northerly outflow winds to increase across southcentral. Right now it’s looking like 20-30mph winds along the ridges with stronger gusts in favored areas. How this will impact Turnagain Pass is unknown at this time. Stay tuned.
PRECIPITATION 24-hour data (6am – 6am)
Temp Avg (F) | Snow (in) | Water (in) | Snow Depth (in) | |
---|---|---|---|---|
Center Ridge (1880′) | 16 | 1 | 0.1 | 60 |
Summit Lake (1400′) | 9 | 0 | 0 | 20 |
Alyeska Mid (1700′) | 17 | 1 | 0.1 | 58 |
RIDGETOP 24-hour data (6am – 6am)
Temp Avg (F) | Wind Dir | Wind Avg (mph) | Wind Gust (mph) | |
---|---|---|---|---|
Sunburst (3812′) | 8 | NE | 6 | 31 |
Seattle Ridge (2400′) | 12 | E | 3 | 8 |
Date | Region | Location | Observer |
---|---|---|---|
05/13/24 | Turnagain | Observation: Eddie’s, Sunburst, Seattle, Cornbiscuit, Pete’s South | H Thamm |
05/13/24 | Turnagain | Observation: Turnagain Pass non-motorized side | Amy Holman |
05/12/24 | Turnagain | Observation: Warm up Bowl | Tony Naciuk |
05/07/24 | Turnagain | Observation: Turnagain Pass Wet Slabs | A S |
04/29/24 | Turnagain | Avalanche: Turnagain aerial obs | Tully Hamer |
04/27/24 | Turnagain | Observation: Johnson Pass | Noah Mery |
04/23/24 | Turnagain | Observation: Turnagain Sunny Side | Travis SMITH |
04/21/24 | Turnagain | Observation: Bertha Creek | Anonymous |
04/20/24 | Turnagain | Avalanche: Spokane Creek | Schauer/ Mailly Forecaster |
04/16/24 | Turnagain | Observation: Cornbiscuit | Krueger / Matthys Forecaster |
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