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The avalanche danger is MODERATE above 1000′ where triggering a wind slab will be possible. Additionally, old weak layers deeper in the snowpack may be triggered, creating a larger avalanche. Evaluate snow and terrain carefully.
**If headed South of Turnagain Pass be aware of recent avalanche activity in Summit Lake and Lost Lake zones. For observations from Summit Lake click HERE and Lost Lake click HERE.
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. Dangerous avalanche conditions. | 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. |
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 |
Be aware of wind slabs on a variety of aspects due to unusual wind loading patterns and cross loading. Strong Northwest winds this week have transformed a foot of new snow into variable surfaces. Ridgetops are scoured down to old anti-tracks, sastrugi or wind polished snow. Smooth supportable surfaces where the snow is hollow sounding are suspect, especially if the slope is unsupported. Identify terrain features with a pillow-shaped look where triggering a wind slab could break above you. Shooting cracks may not be present until committed to a slope and the whole slab releases. Several weak layers have been preserved ~2 feet below the surface and could propagate a larger avalanche. (More on this below.) Although the sun is not expected today, keep in mind that its that time of year when radiation can make the snow more reactive on Southerly aspects.
Scoured ridges and wind pillowed snow on Tincan following the big wing event this week.
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 |
Triggering an avalanche 2+ feet thick is possible due to several weak layers buried within our snowpack. More potential exists on the Southern end of Turnagain Pass and Summit Lake zone where a shallow and weaker snowpack remains. This was evident on Wednesday during the wind event where numerous large avalanches released naturally near Silvertip Creek and in Summit Lake. In Turnagain Pass we have been tracking several weak layers buried 1-2 feet deep (facets and buried surface hoar) and both have been reactive in stability tests. This structure can be found on all aspects and will be easier to trigger in thinner areas of the snowpack. These slabs could be triggered in softer more protected snow or in places where the snow is harder and more supportable. Assess the terrain for consequences and remember that the bigger the terrain the bigger the consequences. There is still much uncertainty around this avalanche problem.
Deep Persistent Slabs: Keep in mind that there are deeper persistent layers that could ‘wake up’ if you find the wrong spot above 3,000′ in the Alpine. At these high elevations, old weak layers of facets and buried surface hoar sit in the bottom half of the snowpack. This structure is also more pronounced in places with a thin overall snow cover, such as the South end of Turnagain Pass, the Summit Lake area and Crow Pass.
Several observers this week have reported collapsing below 2500′ and is likey because of a layer of facets sitting on m/f crust. Photo of W aspect of Cornbiscuit at 2000′
Large connected crown on a Northeast aspect near Silvertip Creek which released naturally some time between Tuesday and Wednesday during the wind event.
Yesterday was cold, clear and sunny. Day time temperatures warmed into the upper teens F’s from single digits at all elevations. Winds were light and variable and no precipitation occurred. Overnight clouds moved into the area and temperatures increased into the low 20F’s.
Today expect overcast skies and temperatures to remain in the 20F’s in the alpine with cooler temps at valley bottoms creating some valley fog. A few snow flurries may arrive late afternoon and ridge top winds will remain light from the West.
This weekend low pressure is tracking just North of us and will favor Mat-Su Valley, but we may see a few inches by Saturday. Some uncertainty exists around winds. Depending on how far North the low tracks, we may see an increase in gap winds again in Coastal areas. Temperatures are expected to range from the teens F to mid 20s F. Skies are expected to clear again on Sunday with another storm is expected on Monday night into Tuesday, but again will favor the Northern areas.
PRECIPITATION 24-hour data (6am – 6am)
Temp Avg (F) | Snow (in) | Water (in) | Snow Depth (in) | |
Center Ridge (1880′) | 15 | 0 | 0 | 70 |
Summit Lake (1400′) | 4 | 0 | 0 | 29 |
Alyeska Mid (1700′) | 14 | 0 | 0 | 61 |
Temp Avg (F) | Wind Dir | Wind Avg (mph) | Wind Gust (mph) | |
Sunburst (3812′) | 17 | W | 4 | 15 |
Seattle Ridge (2400′) | 16 | Variable | 3 | 13 |
Date | Region | Location | Observer |
---|---|---|---|
11/16/23 | Turnagain | Observation: Tincan Common | William Finley |
11/14/23 | Turnagain | Observation: Sunburst/Magnum | Adrian Beebee |
11/14/23 | Turnagain | Observation: Seattle Ridge | Schauer/ Creighton/ Ellis Forecaster |
11/13/23 | Turnagain | Avalanche: Tincan Trees | Eeva Latosuo |
11/12/23 | Turnagain | Observation: Sunburst | Schauer/ Creighton/ Nave Forecaster |
11/12/23 | Turnagain | Avalanche: Goldpan – avalanche | Mike Records |
11/11/23 | Turnagain | Observation: Tincan Common | Andy Moderow |
11/11/23 | Turnagain | Observation: Taylor Pass – Sunburst | Wadsworth / Stwertka |
11/10/23 | Turnagain | Observation: Tincan | Andrew Schauer Forecaster |
11/10/23 | Turnagain | Observation: Tincan Trees | Michael Kerst |
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