|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|
‘Twas the night before Christmas, when all through the hills,
Neither skier or rider was looking for thrills.
With a blast of wind and light snow falling,
There were hopes of blue skies in the early chill morning.
Happy Holidays everyone! And, that’s right, many folks are hoping for some clearing skies today after a quick pulse of moisture and wind moved in last night. This brought 4″ of new snow to the mid elevations and ~6″ to the higher elevations. Ridgetop winds picked up from the east averaging 25-35 mph for a period of 8 hours last night with gusts to 56mph on Sunburst. Since then, winds have been steady around 20mph with gusts near 40mph; where they are expected to remain today. With around 6-10+” of existing loose snow on the surface and other 6+” from last night in the high elevations, we can expect to find some wind loaded slopes and touchy wind slabs today. The good news is, new wind slabs should be easy to identify and relegated to the higher terrain. Seeking out areas without wind effect will be your best bet for fun riding conditions and avoiding a wind slab avalanche.
Wind slab avalanches: Triggering a fresh wind slab is the main concern today. If skies clear enough for travel into the bigger terrain watch for:
Cornices: As always, watch for cornices and give them a wide berth.
Loose snow sluffs: If you are lucky enough to find a slope without wind effect and lots of loose snow, watch your sluff.
Warm-up Bowl (-1 Bowl) avalanche from Wednesday 12/23 – UPDATE:
We were able to get a look at the large avalanche triggered on the backside of Seattle Ridge yesterday. This slide was 2-4’+ feet deep, 1,000′ wide and ran around 800 vertical feet. It was triggered by a snowboarder who was the 5th person down the slope. The boarder deployed their airbag and when the debris settled, was buried up to their neck. They are thankfully OK and a few more details can be found HERE (from the boarder involved) and HERE.
Much of the crown face can be seen in the photo below with its wide propagation. This did turn out to be a large wind slab that had not bonded yet after Tuesday’s 2-3′ of snow and extremely strong winds. The weak layer was precipitation particles (stellar crystals) and not a persistent weak layer – however, these stellars can act like a persistent grain type for a few days before bonding, hence the wide propagation. Today is day three, and there just might be a lurking larger wind slab not yet bonded under the new smaller slabs formed overnight.
Warm-up Bowl avalanche from Wednesday 12.23.20. Photo: Anonymous
Crown face of one section of the slide. The crown was 2′ thick here but grew to over 4′ in sections. Photo taken 12.24.20.
What to do about those old October facets near the ground in the shallow snowpack zones? In Summit Lake and the central Kenai Mtns the snowpack is much thinner than Turnagain Pass. This area is outside our forecast zone, but we want to be sure folks know the difference in snowpack. As Aleph mentioned yesterday, this layer continues to show less and less reactivity over time and triggering an avalanche releasing near the ground is unlikely. Because of all the crusts in the mid-pack from 2,500 and below, this issue would be above, in the Alpine, where no crusts exist.
Yesterday: Overcast to obscured skies filled the region. Light snow started falling in the evening with rain below 500′. Accumulations are in the 4″ range at mid-elevation and 6″ in the Alpine. Easterly ridgetop winds bumped up with the precipitation and have averaged 20-35mph with gusts into the 50’s for a 8 hour period ending at midnight. Temperatures were warm, in the mid 20’s F along ridgelines and mid 30’s below 1,000′.
Today: Cloudy skies and light precipitation will slowly move out this morning and and skies should begin to clear by midday. Ridgetop winds are expected to average in the 10-20mph range and decrease as the day goes on. Temperatures will start to cool off with the clear skies and possibly it the teens along the ridgetops and mid 20’s F in the parking lots.
Tomorrow: Another round of wind and snow is on tap for tomorrow. This is a cooler and quick moving system which should bring a few inches of snow, even to sea level. Models are showing another larger scale precipitation event for early next week. This one also looks to be on the cooler side with snow close to sea level. Stay tuned!
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||30||4||0.4||80|
|Summit Lake (1400′)||25||0||0||31|
|Alyeska Mid (1700′)||30||4||0.4||78|
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||25||*N/A||*N/A||*N/A|
*Seattle Ridge anemometer is rimed over again and not reporting wind data.
|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|
|04/15/21||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|
|04/10/21||Turnagain||Observation: north sides||lance breeding|
|04/09/21||Turnagain||Observation: Girdwood to Turnagain Road Observations||W Wagner Forecaster|
|04/05/21||Turnagain||Avalanche: Resort bowl Seattle creek head wall||Clint Kyffin|
|04/04/21||Turnagain||Observation: Center Ridge||Andy Moderow|
|04/03/21||Turnagain||Observation: Repeat Offender – Seattle Ridge||Troy Tempel|
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: firstname.lastname@example.org
|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.