|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 last known significant avalanches occurred during and just after last week’s storm. This includes multiple avalanches that failed on weak layers buried deeper in the snowpack in Girdwood, the south end of Seattle Ridge, Lipp’s, and Pete’s North.
A relatively smaller avalanche failing in the new snow from last week triggered this deeper pocket on the north side of Lipps. This is on the smaller side of the avalanches that we saw fail on the deeper weak layers- some of which were 500′ wide or more. 12.18.2022
|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
The main concern for today is triggering an avalanche on weak, faceted snow associated with a crust that formed just before Thanksgiving, now buried around 2-4′ deep. Persistent weak layers like this are difficult to predict, and are common culprits in avalanche accidents. As we get farther out from our last significant loading event (now 4 days ago), the layer is becoming more stubborn, and we are seeing fewer warning signs of unstable snow. This doesn’t mean the problem is gone. We had multiple poor test results yesterday on Cornbiscuit (details), not far from where multiple other groups observed large collapses and shooting cracks over the weekend (details here and here). These are clear signs that the snowpack is still capable of avalanching. On the other hand, there are tracks all over steep terrain around Turnagain Pass, so we know that the likelihood of triggering an avalanche is decreasing overall. We suspect the most dangerous conditions are in the mountains closer to Girdwood, as well as on the south end of the pass. Both of these zones saw the most avalanche activity following the last storm.
The only way to manage a problem like this is by careful terrain management. Give yourself wide margins for error by avoiding steep, consequential terrain. This includes big, connected terrain features and steeper slopes above terrain traps like gullies, rocks, or trees. Ask yourself, what would happen if this slope were to avalanche? Persistent slab avalanches have a nasty tendency to release after there are multiple sets of tracks on a slope, or after a person gets way out into the middle of a slab.
Dry Loose Avalanches: With several days of clear, cold, and calm weather, there is plenty of soft snow on the surface. This will make dry loose avalanches (sluffs) likely in steep terrain. While these are unlikely to become big enough to bury a person, they can be dangerous if they carry you into terrain traps.
The poor structure in this snowpit is fairly consistent across the advisory area. Those test results highlighted in red suggest the snowpack is still capable of producing an avalanche. That is the layer we are concerned about. Photo: Andy Moderow. 12.18.2022
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Yesterday: We had another day of clear, calm, and cold weather with temperatures struggling to get above 0 F in the valleys, but an inversion brought temperatures into the low teens F at higher elevations. Winds were light and variable, with no precipitation.
Today: Today is looking like another day of quiet weather, with high temperatures making it into the mid teens F and overnight lows getting back down into the single digits F. Winds should be light out of the east, with no precipitation during the day. We are expecting scattered clous, and there is a chance we might see some flurries tonight, but it shouldn’t be any significant precip.
Tomorrow: Cloud cover will build tonight into tomorrow, with light flurries possible and high temperatures in the low to mid teens F. Winds should be light out of the east to northeast. The next round of snow is looking to arrive Wednesday evening, with around 3-6″ overnight into Thursday.
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′)
*Winds shifted directions around 6:00 p.m. yesterday.
|Observation: Silvertip Creek
|Observation: Seattle Ridge
|John Sykes Forecaster
|Observation: Kickstep NE Bowl
|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