|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.|
We did not hear of any avalanche activity in our forecast zone yesterday. The last known avalanches were from early Thursday morning after the last snowfall/wind. Pictured below are some of the larger slabs that likely released around this time on Lipps and Pete’s North, photographed yesterday.
Large slab on the west face of Lipps ridge that appears to have broke in weak snow near the Thanksgiving crust. Andy Moderow 12.17.22.
Several avalanches on the SW face of Pete’s North. One has especially wide propagation, indicative of an avalanche breaking in a buried weak layer rather than just a storm slab avalanche. Andy Moderow, 12.17.22.
|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|
Thank you for all the report-outs from people in the mountains yesterday! We heard of a few large ‘whumpfs’, but no avalanches. We also heard of folks that didn’t see any signs of instability. It is becoming clear however, that the weak faceted snow above and below the crust formed just before Thanksgiving is concerning in many areas; mostly in shallower areas such as the south end of Turnagain Pass, Lynx Ck, and Silvertip. Also, the Girdwood Valley has proven to be a problem spot as well. That said, with a few more clear sky days and easy travel, we still need to approach the slopes with extra caution. We are in one of those ‘scary’ MODERATE phases.
Hence, triggering a slab avalanche that breaks 1.5-3 feet deep is possible. This kind of avalanche could be triggered remotely, meaning from the bottom, sides, or on top of a slope. It could also release after several people have been on the slope. There may be NO signs of instability before an avalanche is triggered. This can set us up to think all may be fine until it is not. Good ways to manage this are to take extra care to travel one at a time in avalanche terrain, whether you are ascending or descending. Consider travel routes to limit exposure, always have escape routes planned, and watch your partners. Choosing lower angle slopes, 30 deg or less, can be a good way to just avoid the problem for those of us with lower risk thresholds. That said, if you hear a ‘whumpf’ that’s a problem and re-evaluating your plan, as several groups have done in the past few days, is prudent.
Weak faceted snow found above and below the Thanksgiving crust. This was around 2,300′ on a NE aspect in the Notch area of Girdwood Valley. The slab was around 2.5′ thick and composed of all the December storm snow. Ethan Tyler, 12.17.22.
Yesterday: Cold and clear! Minus single digits in valley bottoms and teens to even 20F along the ridgelines due to an inversion in place. Ridgetop winds were light from the east to SE.
Today: Clear skies and cold temperatures will remain today. However, the inversion has weakened slightly with ridgelines remaining in the teens. Winds along the ridgetops should be calm to light from a northerly direction.
Tomorrow: Partly sunny skies, cold temperatures, and light easterly winds are expected through Tuesday. Clouds move in along with a chance for a few flurries on Wednesday. The next shot for decent snow amounts looks to be Friday into next weekend.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||18||0||0||39|
|Summit Lake (1400′)||-2||0||0||29|
|Alyeska Mid (1700′)||17||0||0||42|
|Bear Valley (132′)||-5||0||0||–|
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||21||SE||4||10|
|12/06/23||Turnagain||Observation: Eddies||N Dumont|
|12/05/23||Turnagain||Observation: Sunburst||Kakiko Ramos-Leon|
|12/04/23||Turnagain||Observation: Lynx Creek||Schauer / Keeler/ Predeger Forecaster|
|12/04/23||Turnagain||Observation: Sunburst, 2400′ – 3100′ NW ridge common uptrack.||Arnav Verma|
|12/03/23||Turnagain||Observation: Center Ridge||Amy Holman|
|12/03/23||Turnagain||Observation: Magnum||Tony Naciuk|
|12/03/23||Turnagain||Observation: West ridge of Tincan Peak and Peak 4400||Kelli Spencer|
|12/03/23||Turnagain||Observation: Lipps||Paul Schauer|
|12/02/23||Turnagain||Observation: Seattle Ridge||Schauer / Keeler Forecaster|
|12/02/23||Turnagain||Observation: Tincan South Side||Anonymous|