|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.|
Another day, another storm. Since the last dry spell, just before Christmas and during the Solstice, we have seen roughly 8 feet of snow fall above treeline (a rain/snow combo below this). During this time we have also seen alders continue to be laid over and covered up, terrain features smoothed out and, as of today, a 13 minute gain of daylight. Just overnight, another intense pulse of moisture added 20+” of dense snow at treeline on Turnagain Pass with a rain/snow line around 800′. Precipitation and wind has abated this morning, yet the avalanche conditions remain dangerous.
If you are thinking of heading to Turnagain Pass today, keep in mind the mountains have just received a ‘rapid loading’ event. Not only is 20+” of new snow loading slopes (2.5″ of water equivalent), but very strong Easterly winds have loaded leeward slopes and cross-loaded gullies. Wind slabs in the new snow could be as thick as 6′ in places.
Many different avalanches are possible today:
1) Wind slab: Triggering a wind slab 2-6’ thick is likely on steep wind loaded slopes. Winds are forecast to remain from the East in the 20-30mph range. If this is the case, fresh and sensitive wind slabs will remain through the day.
2) Cornices: With such strong winds and warm snow at the ridgetops, we can expect cornices to be tender! Not only can these trigger an avalanche below, but may also trigger a slide breaking deeper in the snowpack – creating a very large avalanche.
3) Wet loose avalanches: More rain on snow will saturate the upper layers of the snowpack below 1500’. This is more of a concern in areas with terrain traps and in steep channeled terrain where an avalanche from above will be impossible to escape.
Yesterday’s field day, just prior to the heavy snowfall, showed the December storm snow bonding well at the mid-elevations. Keep in mind as you watch the video that another 20+” of snow has fallen.
As mentioned in the video above, sitting under 5-7′ of settled storm snow sits an old layer of faceted snow above the Thanksgiving Rain Crust (TRC). This layer extends to around 3,000′ and continues to be on our radar. Over the past several days, we have had reports of avalanches breaking into older weak snow, this is primarily in the periphery of our advisory area such as Summit Lake and Girdwood Valley. As the snowpack gets yet another load, we will be monitoring whether slides are breaking in older/weaker snow.
Obscured skies and strong Easterly winds were over the area yesterday. Light snow fell above 1,500′ while rain fell below 1,400′. Beginning yesterday evening, snowfall increased and the rain/snow line dropped to ~800′ at Turnagain Pass. Overnight, we have seen over 2″ of water equivalent from Girdwood to Turnagain Pass.
As of this morning, the main ‘fire hose’ of sub-tropical moisture has moved off to the East, yet strong Easterly winds and light snowfall will remain today. The rain/snow line should remain just below 1,000′ and we could see another 2-5″ of snow at the mid-elevations. Winds are forecast to average in the 20-30mph range from a generally East direction. Temperatures will remain in the mid 20’s F on the ridgetops and the low 30’sF at 1,000′.
This warm and stormy pattern looks to be over us through Monday with a possible break between storm Tues/Wed.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||31||20||2.5||89|
|Summit Lake (1400′)||33||8||0.8||26|
|Alyeska Mid (1700′)||32||9 (very wet snow)||2.2||64|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||27||N/A||N/A||N/A|
|12/01/23||Avalanche: Sunburst||John Sykes Forecaster|
|12/01/23||Turnagain||Observation: Eddie’s trees||Anonymous|
|12/01/23||Turnagain||Observation: Turnagain – God’s Country||Graham Predeger Forecaster|
|11/30/23||Turnagain||Avalanche: Tincan Trees||Kakiko Ramos-Leon|
|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|