|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.
PERSISTENT SLAB AVALANCHES (In our current case: Hard WIND SLABS SITTING ON WEAK SNOW): A big wind event that occurred on December 30th has stripped many Southern and Western ridgetops and left an unusual loading pattern for our region; loading Northern and Eastern aspects. This wind event as well as the Christmas snow storm (a week ago) caused widespread avalanching in the area. Several persistent weak layers are buried within the snowpack (facets and buried surface hoar), but strong supportable snow may make it tough to find the right trigger spot.
Some uncertainty remains today with how the warm inverted air temps (approaching 40F) will affect the snowpack in the alpine. Although radiation from the sun at this time of year is minimal, whenever temperatures remain above freezing for 24 hours it is worth keeping in the back of your mind. Be skeptical of supportable and hollow sounding snow on steep slopes. Likely trigger spots will be in thinner areas of the snowpack in steep rocky terrain or on unsupported slopes that haven’t avalanched. Triggering a small isolated wind slab or a deeper slab 2+ feet is becoming more difficult, but is possible for a person or snowmachine to tip the balance. Obvious signs like cracking and ‘wumpfing’ are becoming less common and may not be an early warning sign.
Before exposing yourself to steeper terrain, ask yourself what will happen if the slope slides? Always practice safe travel habits to minimize exposure in avalanche terrain!
A closer view of the natural avalanches that occured on Corn Biscuit’s North facing chutes last Friday (12/30.) Places that haven’t avalanched with similar characteristics (rocky starting zones, top loading and cross loading) remain suspect.
Most of the snow along Southern aspects have blown away making it unlikely to trigger an avalanche in these areas.
Yesterday skies were sunny and clear with light Northwest winds. A large temperature inversion was observed, 12F at 1000′ and 33F at ridge tops, which caused valley fog in Turnagain Arm.
Overnight ridge top temps increased into the high 30F’s Turnagain Pass and low 40F’s in the Girdwood Valley. Valley temps have remained around 10F. Winds have remained light and no precipitation was recorded.
Today expect a similar inverted weather pattern with above freezing temperatures in the alpine and temperatures near 10F in valley bottoms. This will trap dense Valley fog in and along Turnagain Arm.
|Temp Avg (F)
|Snow Depth (in)
|Center Ridge (1880′)
|Summit Lake (1400′)
|Alyeska Mid (1700′)
|Temp Avg (F)
|Wind Avg (mph)
|Wind Gust (mph)
|Seattle Ridge (2400′)
|Observation: TinCan Backdoor/ Center Ridge
|AAS L1 Turnagain
|Avalanche: Lynx Creek
|Observation: Turnagain, Seattle, Mt Ascension
|Silverton Mountain Guides
|Observation: Tincan Trees
|Dalpes/Thamm/ Schauer Forecaster
|Observation: Seward Highway across from Johnson Pass TH
|Avalanche: Base of Seattle Ridge
|Troy Tempel, Thomas Lees, .Josh Bollaert, Damian Naquin
|Observation: Lynx creek
|Observation: Tincan Trees
|Moderow / Clayton