|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 storm ended yesterday, and left a blanket of fresh snow across all elevations and aspects of the mountains. This is good news for backcountry quality, but makes it difficult to identify the areas of greatest concern. Wind during the storm was trending from the east, so westerly aspects may be harboring wind pockets and larger cornices.
A big piece of information came in yesterday from Seward highway/AKRR crews when they triggered a large avalanche near Kern creek. The avalanche below was larger than anything we’ve seen in quite some time. This begs the question – Is it still possible for a person to trigger a larger avalanche today? It seems unlikely, but perhaps not impossible. We think that areas closer to Girdwood may be somewhat less stable than Turnagain Pass. This is due to greater snowfall in the recent storm cycles, and a more prominent crust/weak layer combination that has shown it can cause big avalanches.
Other storm related issues to think about –
1. Wind loading up high – few people have ventured above 2500 feet in the last week due to poor visibility and stormy weather. Watch for wind slabs in steep terrain. This is a wild card, for which we currently don’t have a lot of information.
2. Cornices – are likely to be large and unstable. We found very small cornices to be easily triggered on Thursday.
3. Loose sluffs – Steep terrain may have enough loose powder to entrain and pick up volume.
In Turnagain Pass, we have seen occasional pits that indicate avalanche propagation is possible on a melt/freeze crust that typically varies from 1-3 feet in depth. This problem is not evident everywhere… The most reactive elevation seems to be between ~1900 and ~2900 feet. It has shown itself to be worse in Girdwood than Turnagain Pass.
The video in this link illustrates the nature of the crust problem. It isn’t easy to initiate, but when it does it may propagate into deeper layers.
The last burst of snowfall which ended yesterday was the highest daily snowfall we’ve had in a month at Turnagain Pass. Over the last week the snow has been piling up, slowly but surely. Above treeline elevation is more than a foot of new snow in the last 48 hours with closer to 3 feet in the last week. The storm had some strong wind over the last few days, which diminished Thursday evening before the snowfall ended. Temperatures also dropped as the storm ended, placing light density, unconsolidated snow (powder) at the surface. Currently temperatures are in the teens at low elevations and single digits at higher elevations.
Today, mostly sunny skies are expected. Wind is moderate currently but will become light by late morning. Snow and wind is back in the forecast tonight, leaving a short window of good weather for today.
Wendy will issue the next advisory on Sunday morning 2-17.
|11/27/23||Turnagain||Avalanche: Tincan Ridge||Schauer/ Stiassny Forecaster|
|11/26/23||Turnagain||Observation: Road report: Slide with dirt on Repeat offender||Anonymous|
|11/26/23||Turnagain||Observation: Pete’s North||Ben Sullender|
|11/25/23||Turnagain||Observation: Tincan trees||John Sykes Forecaster|
|11/21/23||Observation: Spokane Creek||John Sykes Forecaster|
|11/19/23||Turnagain||Observation: Magnum – PMS Bowl||Schauer/ Cullen/ Jonas Forecaster|
|11/19/23||Other Regions||Observation: Sunnyside/Penguin||Jose Ramos-Leon|
|11/19/23||Turnagain||Observation: Eddies||Andy Moderow|