|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 stormy day made it hard to see the extent of avalanche activity in the backcountry yesterday. However, we did get a couple reports of small pockets of 2 feet deep storm slabs that people were able to trigger on small slopes and rollovers in the trees.
Additionally, a large avalanche was seen in motion near Girdwood; seen from the Seward Highway running almost to sea level.
Andrew noticed this debris in motion yesterday afternoon as he was driving between the Portage Curve and Girdwood. 11.30.23.
An example of a storm slab in terrain that is not steep enough to slide, except for a small rollover. Photo by Kakiko Ramos-Leon, 11.30.23.
|Size (D scale)
|Unlikely to bury a person
|Can bury a person
|Can destroy a house
|4 & 5
|Can destroy part or all of a village
It seems the word is out. After a potent 2-day storm deposited 2 – 3 feet of snow, skies are clearing and temperatures are cooling today and through the weekend. The stoke is high but caution is warranted as we head into the mountains.
First, ridgetop easterly winds continued to blow last night. Sunburst reported gusts at 60mph just after sunset and this morning winds are 15-20mph gusting near 30. The snowfall ended right around midnight. That said, today we are less than 24 hours from the end of the storm and in the prime window for human triggered avalanches.
How quickly the snowpack will stabilize is the question. Typically it takes 1-2 days without any funny weak layers. So as we gather more information, our message is to err on the conservative side with our terrain choices, sticking to the lower slope angles and smaller slopes. Keep your eyes peeled for evidence of recent avalanches, this is a great clue as to how the storm snow bonded to the old Thanksgiving crust. *But keep in mind the absence of recent avalanches may just mean they were covered back up at the end of the storm. Once again there are two main types of avalanches we are most concerned with:
Storm Slabs: On slopes over 30 degrees, and especially on the steeper slopes (40 deg and above), it could still be easy to trigger an avalanche composed of the new snow (2-3 feet deep). This would be a large avalanche and certainly unmanageable and dangerous. Shooting cracks and whumpfing may be present, but not necessarily. With such a thick layer of storm snow, these signs can be a bit hidden. The new snow fell on a crust that formed after the Thanksgiving rains and we’ll be watching for how well it bonds over the foreseeable future.
Wind Slabs: We can bet the higher terrain and exposed slopes above the trees harbor all kinds of wind slabs. They could be anywhere from a foot deep to 6 feet deep or more in places. They may or may not be easy to trigger today, but because of their depth could allow a person onto the slope before releasing. Watch for the classic wind slab signs, stiffer snow over softer snow and cracks that shoot out from you.
Cornices: The ridgelines are likely to look a bit different after the storm. Watch for overhanging snow and remember these can break further back than expected.
Storm day conditions at Turnagain. 11.30.23.
Snowpack at the lower elevations of Turnagain Pass. No weak layers found here, just heavy moist snow. Jon Davis, 11.30.23.
Yesterday: The last pulse of a 2 day storm moved through yesterday. Around 12″ of snow fell during the day at Turnagain Pass, Portage Valley, and Girdwood. The rain/snow line fluctuated between 100 and 800′ through the day. Ridgetop winds were strong, gusting near 60mph at times with sustained winds 20-30mph from the east.
Today: Clearing skies, cooling temperatures, and gusty easterly ridgetop winds are forecast today (10-20mph with gusts to 40, quieting in the afternoon). No precipitation is expected. Temperatures should sit in the 20’sF at most locations.
Tomorrow: Mostly clear skies with some high clouds are expected through the weekend. Temperatures will continue dropping, into the low teens by Sunday, with light and variable ridgetop winds. Excellent wintertime weather.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)
|Snow Depth (in)
|Center Ridge (1880′)
|Summit Lake (1400′)
|Alyeska Mid (1700′)
|Bear Valley – Portage (132′)
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)
|Wind Avg (mph)
|Wind Gust (mph)
|Seattle Ridge (2400′)
*Seattle Ridge anemometer is rimed over from the warm storm.
|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