|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 facets buried now by both the Thanksgiving storm and the past weekend’s storm are still reactive and our main layer of concern. Observers reported multiple whumpfs, shooting cracks and a couple of avalanches triggered on both Monday and Tuesday. Quote from an observation on Monday, “I triggered a couple of house sized collapses and then a city block sized collapse at the top of the 10-15 degree willow slopes during the approach. These released above the crust. This was my spookiest trip up Sunburst ever, in hundreds of trips up it.” These red flags are all saying that this snowpack is not to be trusted. Those pesky facets are now buried around 3 feet deep. This means that a slab releasing on them could have high consequences. Snowpack tests yesterday also showed that the facets were reactive with propagation potential but may be a stubborn to initiate. An avalanche may not be triggered by the first person onto the slope but once a failure starts in the weak layer it could travel long distances across terrain and cause a large avalanche. This is not a set-up to mess with. The travel advice for Considerable hazard is important to highlight today.
Remote triggered avalanche on Sunburst 12.4.17 Photo: Chris Flowers
Small avalanche triggered yesterday on Tincan. Note the slab depth. (Thanks to anonymous observer for sharing)
Pit profile at 2250′. The facets are sitting on an old melt freeze crust 20 cm above the ground.
Very high winds (over 100 mph) during the storm Saturday have loaded leeward slopes. An additional 4-6″ of snow fell yesterday and ENE winds blew 15-25 mph with gusts as high as 60. Winds slabs are likely found along ridgelines as well as lower down slopes due to those high wind speeds on Saturday. Look for drifting or areas that look “fat”. Pay attention to cracking and hollow sounding snow. Wind slabs could be soft or hard depending on exposure to winds and if triggered could release a larger persistent slab lower down on the slope. Today is not the time to be pushing into steep terrain. Avoiding slopes greater than 30 degrees is recommended.
Wind loading on leeward slopes, CFR.
Yesterday skies were overcast in the morning with rain showers at sea level and snow falling above approximately 700′, adding 4-6″ of snow to the snowpack. The precipitation tapered off and the skies became broken in the afternoon. Winds were easterly 15-25 with higher gusts into the 50-60s. Temperatures were in the mid 30Fs at sea level and the mid 20s at ridgeline stations. There was slight cooling overnight.
Today is forecasted to be mostly to partly cloudy with a chance of snow showers in the morning. Winds will shift to the north, 5-15 mph. Temperatures will be low to mid 30Fs at 1000′ and low to mid 20Fs at 3000′. Temperatures should dip into the low 20Fs overnight but then climb again Thursday morning as the next wave of forecasted moisture moves into the area. Again timing, precipitation amounts and temperatures are not certain. The models are having trouble with these waves beyond 24 hrs out according to the NWS. Stay tuned. Into the weekend looks to be stormy! For a good visual of the atmospheric river that is sending all the weather into the Gulf of Alaska check out Windy.com.
*Center Ridge SNOTEL is reporting erroneous temperature data. See Turnagain Pass DOT weather station for accurate temperature at 1000′.
**Seattle Ridge anemometer is rimed.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||32*||4||.3||32|
|Summit Lake (1400′)||30||1||.1||12|
|Alyeska Mid (1700′)||33||5||.4||20|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||27||n/a**||n/a**||n/a **|
|12/04/23||Turnagain||Observation: Lynx Creek||Schauer / Keeler/ Predeger Forecaster|
|12/04/23||Turnagain||Observation: Sunburst, 2400′ – 3100′ NW ridge common uptrack.||Arnav Verma|
|12/03/23||Turnagain||Observation: Center Ridge||Amy Holman|
|12/03/23||Turnagain||Observation: Magnum||Tony Naciuk|
|12/03/23||Turnagain||Observation: Lipps||Paul Schauer|
|12/02/23||Turnagain||Observation: Seattle Ridge||Schauer / Keeler Forecaster|
|12/02/23||Turnagain||Observation: Tincan South Side||Anonymous|
|12/02/23||Turnagain||Observation: Eddies up track||Luc Mehl|
|12/01/23||Avalanche: Sunburst||John Sykes Forecaster|
|12/01/23||Turnagain||Observation: Eddie’s trees||Anonymous|