|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|
It’s a day to carefully evaluate terrain and consequences if an avalanche does release. We need to give the mountains time to adjust to the rapid loading. Low angle slopes without steep slopes above are great ways to enjoy the new snow without worry. Yesterday’s powerful storm brought feet of snow to the mid and upper elevation terrain, inches of rain to sea level and multiple hours of sustained winds at ridgetops blowing 60-90 mph (with gusts as high as 129 mph on Maxs and 133 mph on Sunburst). The rain/snow line rose to around 1,000′ and then dropped back to close sea level overnight. Not surprisingly there was a widespread avalanche cycle observed from the highway.
Storm totals (beginning Monday afternoon through 6 am Wednesday morning)
Today’s partly cloudy skies may allow for easier travel above treeline and with that, the danger that a person could trigger a large avalanche if venturing into avalanche terrain. Two to three feet of new snow has fallen in the mountains. There are a variety of storm snow related issues to pay attention to and view as likely today starting with wind slabs. Very strong winds can have unusual loading patterns. Sometimes wind slabs are farther down onto slopes than expected and terrain channeling of the wind can significantly cross-load terrain features. In sheltered areas (if were any) storm slabs may be present as heavy warm snow fell on light colder snow. Avoid travel on or under cornices as they may be quite tender today and often break farther back than expected. At low elevations that received heavy rain, wet loose avalanches may still be initiated before the next crust forms.
Red flags to watch for:
– Recent avalanches, from today or avalanche activity from during the storm?
– Whumpfing (collapsing) of the snowpack, sure sign to avoid avalanche terrain period.
– Shooting cracks, likely to be seen near ridgelines and on slopes where the wind has formed wind slabs.
The good news is the new snow should bond relatively quickly. From what we know, the pre-existing snow surface lacked any persistent type of snow grain and was mainly wind slab and settled powder. However as always, the snowpack is guilty until proven innocent and there are always surprises out there – it’s the first day after a storm and we can’t get caught being over confident.
Deep Persistent Slabs:
Above 2,500′ there is a layer of facets (weak snow) at the base of the snowpack, now 5-8′ deep. There is a chance this storm may have brought it back to life in places – meaning the rapid loading of new snow and wind may have overloaded the layer causing it to collapse and initiate very large avalanches to the ground. However, that has yet to be determined and is something we will be looking for as we get eyes on the forecast area and south of it towards Summit Lake.
Yesterday: Skies were obscured and heavy and rain and snow fell throughout most of the day with precipitation rates of 1-2″of snow an hr. Rain/snow line was around 1000′. Winds were easterly and very strong blowing 60-90 mph for close to 12 hrs with peak gusts over 120 mph. Temperatures were in the 20°Fs in the Alpine and the high 30°Fs at sea level. Around 1 am winds and precipitation eased off. Overnight temperatures were in the mid 20°Fs to mid 30°Fs. The storm ended with light snow falling to close to sea level.
Today: Skies are forecast to be partly cloudy today with a chance of light snow showers. Winds will be calm and temperatures will be in the mid 20°Fs to mid 30°Fs. Overnight skies will remain partly cloudy with scattered showers possible, winds will be light and easterly and temperatures will be in the 20°Fs.
Tomorrow: Mostly cloudy skies with snow showers and east winds 10 to 15 mph increasing to 20 to 25 mph in the afternoon. Winds could gust as high as 40 mph. Temperatures will be in the mid 20°Fs to mid 30°Fs. Looking ahead there is sunshine on tap for Christmas Day.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||31||22||2.8||84|
|Summit Lake (1400′)||32||6||0.8||34|
|Alyeska Mid (1700′)||31||30||2.85*||83|
*Alyeska Mid – precipitation gauge blew away. Numbers extrapolated from Alyeska Base.
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||25||SE||19||49|
|04/19/21||Turnagain||Avalanche: Triangle, Seattle creek||Will Morrison|
|04/18/21||Turnagain||Avalanche: Turnagain Pass Road Obs||Andy Moderow|
|04/18/21||Turnagain||Observation: Seattle Ridge, approximately 300 yards south of the up track||Brent Byrne|
|04/17/21||Turnagain||Avalanche: Road obs||Johnston-Bloom / Moderow Forecaster|
|04/16/21||Turnagain||Avalanche: Seattle Ridge||Wendy Wagner Forecaster|
|04/16/21||Turnagain||Avalanche: Turnagain Pass, non-motorized side seen from Seattle Ridge||CNFAIC Staff Forecaster|
|04/16/21||Turnagain||Observation: Sunburst||Lance breeding|
|04/15/21||Turnagain||Observation: Tincan||Schauer/ Rothman Forecaster|
|04/13/21||Turnagain||Observation: Turnagain Pass Road Obs||A Schauer Forecaster|
|04/12/21||Turnagain||Observation: Tincan||Johnston-Bloom / Latosuo Forecaster|
Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: email@example.com
|Area||Status||Weather & Riding Conditions|
This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.