|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 last observed avalanche activity was on Monday, December 12th when Andrew saw several natural avalanches along Seattle Ridge that had released during the storm. These likely released at the interface of the new snow and old snow or on a weak layer a little bit below the old snow surface. We also had observations of avalanches on Tincan and Sunburst during this cycle. Since then visibility has been poor, so observing avalanches is very challenging.
|Signal Word||Size (D scale)||Simple Descriptor|
|Small||1||Unlikely to bury a person|
|Large||2||Can bury a person|
|Very Large||3||Can destroy a house|
|Historic||4 & 5||Can destroy part or all of a village|
A quick storm over the past 24 hours has added about 0.4 to 0.7″ of water to the snowpack which should be roughly 4-8″ of new snow. This storm produced higher snowfall totals for the Girdwood valley compared to Turnagain Pass. A brief period of elevated winds from 6pm to 12am with wind speeds of 10-20 mph and gusts of 30-40 mph will have quickly formed fresh wind slabs, especially in higher elevation areas. There is a lot of light snow on the surface right now, so even though this storm only produced 3-8″ of new snow in our forecast region wind slabs could be up to 2′ deep due to potential for additional wind transport.
The overnight storm system should move out of our area pretty quickly today and winds will switch to the NW at 15-25 mph in areas exposed to gap winds. Likely areas to see stronger winds today include higher elevation ridgelines, Turnagain Arm, Seattle Ridge, and Crow Pass. To identify areas with fresh wind slabs look for active wind transport and feel for areas with stiffer hollow feeling snow on the surface. Using small test slopes can be a good way to check whether wind slabs are reactive in the area you are travelling. We have limited information about conditions at higher elevations since the last big snowfall on Sunday/Monday, so we recommend adopting a conservative mindset if you venture into alpine terrain today.
Loose dry avalanches (aka sluffs) will be a concern in steeper terrain today. To manage this hazard it is important to be mindful of the terrain you are travelling in and make sure your sluff won’t push you into an undesirable location.
Yesterday: Light snow throughout the day with winds averaging 5-10 mph for most of the day except a period from 6pm to 12am when wind speeds increased to averages of 10-20 mph with gusts of 20-40 mph. Snowfall totals range from 4-8″ across the forecast area. Temperatures briefly climbed above freezing at sea level from 8pm to 3am so the precipitation may have come as rain at the lowest elevations.
Today: Snowfall is expected to taper off quickly in the morning and transition to clear skies in the afternoon. Winds will shift from SE to NW as the storm passes and a high pressure system moves into the area. Winds speeds should be in the 15-25 mph range in areas exposed to NW gap winds, like Turnagain Arm and upper elevations. Temperatures will drop from the twenties to teens at upper elevation this afternoon and evening.
Tomorrow: Clear skies should remain through the start of the weekend with winds decreasing on Friday to the 5-15 mph range and temperatures dropping into the teens and single digits over the next few days.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||29||5||0.4||46|
|Summit Lake (1400′)||25||5||0.5||35|
|Alyeska Mid (1700′)||27||8||0.7||48|
|Bear Valley (Portage) (132′)||30||2||0.35||–|
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||25||SE||7||18|
|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|
|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|