|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 natural avalanche activity slowed down as temperatures cooled Sunday and Monday and the freeze was more pronounced. Today and tomorrow it will still be important to pay close attention to how the warming is affecting the pack. We are in a melt-freeze cycle on Southerly slopes – hard frozen crusts in the morning, which turn to unsupportable mushy and unstable snow by the afternoon/evening. Choosing what aspect to travel on, paying attention to the time of day and how long the slope you are on has been exposed to direct sunlight are essential to staying out of trouble. Zones with thin snowpacks have been particularly active where free water is interacting with old weak snow. Wet loose snow avalanches may also trigger deeper slabs. Rocky areas that are absorbing more heat should be avoided.
If heading out for a fun day in the sun keep these points in mind:
Temperature trend from late last week until this morning. The natural wet avalanche activity peaked during the warmest days Friday, April 14th and Saturday, April15th.
Natural wet slab avalanche that occured on Friday afternoon on Seattle Ridge.
Yesterday around 5 pm, a skier triggered a slide on a West aspect in Triangle Bowl on the backside of Seattle Ridge. The skier was the 4th person on the slope and triggered it in a thin spot. They were able to ski off of the slab. The bed surface was reported as the rain crust from the April Fool’s storm. In this springtime transition it is important to remember on the shaded and cooler side of the mountains (Northerly aspects: NE – NW – W), a cold mostly dry snowpack still exists. Afternoon warming may also influence how easy it is to trigger weak layers that are buried anywhere from 2-5′ below the surface. As folks venture out looking for “cold, soft snow” this remains a concern. Shaded aspects (NE – NW – W) in the mid and upper elevations that haven’t avalanched already are the most suspect places for triggering a deeper slab.
This problem is one of low probability but high consequence as these are potentially large and unsurvivable slides.
Keep these points in mind:
Triangle Bowl a few minutes after the avalanche was triggered. Thanks to the party involved for sharing the photo and information.
Several small glide avalanches have released on Southeast facing Seattle Ridge and Eddies Ridge over the past week. We expect this trend to continue with the warm days ahead. Keep an eye out for glide cracks, full depth cracks in the snow, and limit time underneath them.
Glide cracks in Eddies continue to open. Glide avalanche occured on Wednesday April 12th.
Cornices: Cornices are large and likely hanging close to their tipping point. Direct sunshine, a person, or a group of people on top these could be enough to cause one to break. An observer in Seattle Creek noted a large cornice fall on Friday. Cornice crevasses have also been noted (opening slots where the cornice is pulling away from the ridge but has not broken off. Give cornices a wide berth from above and limit exposure under them from below.
Cornice in Summit Lake with old slab crown below.
Yesterday skies were partly cloudy to mostly clear. Winds were light and Westerly. Temperatures were in the high 20Fs at upper elevations and 30-40Fs at lower elevations. Overnight temperatures dropped below freezing.
Today will be mostly clear and sunny. Winds will remain light. Temperatures will be in the 30-40Fs in the valleys and with high 20Fs to low 30Fs forecasted above 3000′. Tonight into tomorrow looks to be very similar with temperatures dropping at night and climbing back up during the day. Clouds may increase Wednesday evening. There is a pattern shift still in the forecast for the weekend. Stay tuned.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||31||0||0||64|
|Summit Lake (1400′)||30||0||0||21|
|Alyeska Mid (1700′)||32||0||0||58|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||No Data||W||3||12|
|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|