As seen in last night’s news, debris from a natural avalanche in Summit Lake covered both lanes of the Seward Highway near Mile Post 45 around 4pm yesterday. One vehicle was pushed to the side of road in the moving debris. This avalanche was one of three naturals that occurred off of Summit Mountain on an ESE aspect with start zones around 3,500′; the other two slides did not run to the road. Due to poor visibility and not being able to see the slopes above, we have little information as to the character of the slides at this time.
Natural avalanche in Summit Lake (MP 45 Seward Highway). 3.30.21.
Debris from slide on the road was around 4-6′ deep and covered around a 100′ stretch.
|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 definitely springtime and with that longer days and warmer temperatures. The snowpack can react in wild ways and yesterday’s natural avalanches have us on guard. This is the number one Red Flag for avalanche potential. With similar, but slightly warmer, weather today, we have to be extra cautious. Triggering an avalanche is still in the ‘possible’ category, which fits a MODERATE danger. What fits CONSIDERABLE is the travel advice on the Danger Scale, ‘cautious route-finding and conservative decision-making’. Poor visibility will likely keep many of us out of larger terrain, but avoiding being under large slopes and sticking to smaller terrain and low angle slopes, under 35 degrees, is just a good bet today.
Snowfall yesterday brought around 4″ of moist snow to the mid elevations and possibly up to 6″ at the high elevations. Precipitation has decreased this morning but may set back in later today with another inch or two. The winds have been steady from a southerly direction in the 5-15mph range with stronger gusts and these are forecast to decrease through the day.
Persistent Slabs: As Aleph described yesterday, wind slabs keep developing over facets or buried surface hoar (persistent weak layers) that have transitioned into persistent slabs as they linger. These are now covered with 4″ or so of new snow and possibly some shallow new wind slabs. Every so often, and what is likely the culprit in the Summit Lake avalanches, is these weak layer(s) fail and produce an avalanche. This remains our concern for people venturing onto steeper slopes. There is a weak layer about a foot down that seems to be our current issue. The natural avalanches on Raggedtop and the skier triggered slab on Tri Tip last week are the most recent human triggered avalanches. Be on the lookout for areas with previously wind-loaded snow and those with any new wind-loading. The most suspect terrain will likely be at upper and mid elevations, immediately below ridgelines, in cross-loaded gullies, and below convexities.
Wind Slabs: Watch for new small wind slabs in the 6-8″ range. These are most likely to be found in the higher terrain along ridgelines where the southerly winds blew enough to move the new snow.
Loose snow avalanches: Expect sluffs on steep slopes in the new snow as well the older loose snow that escaped last weekend’s winds. Wet sluffs are likely in the mid and lower elevations in the new snow as the day warms up. The south slopes may run further as old sun crusts sit under the new snow. While it is unlikely these loose snow avalanches will be big enough to bury you, they can be dangerous if they drag you into terrain traps like cliffs, trees, rocks, or gullies.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880')||28||4||0.4||114|
|Summit Lake (1400')||29||4||0.3||52|
|Alyeska Mid (1700')||27||4||0.4||121|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400')||22||SE||10||14|
|05/18/21||Turnagain||Observation: Tincan Ridge||Joe Kurtak|
|04/30/21||Turnagain||Observation: Sunburst||W Wagner Forecaster|
|04/27/21||Turnagain||Observation: Tincan Ridge||Joe Kurtak|
|04/26/21||Turnagain||Observation: Magnum||Creighton/ Hoople|
|04/25/21||Turnagain||Observation: Sunburst||Nick D'Alessio|
|04/24/21||Turnagain||Observation: Airplane obs||Johnston-Bloom / DiJulia /Hilliard Forecaster|
|04/24/21||Turnagain||Observation: Corn biscuit||Heather Johnson|
|04/23/21||Turnagain||Avalanche: Lynx Ck Drainage||W Wagner Forecaster|
|04/23/21||Turnagain||Avalanche: Sunburst||Eeva Latosuo|
|04/23/21||Turnagain||Observation: Center Ridge Turnagain pass||Joe Kurtak|
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.