The sun made a quick appearance yesterday afternoon and initiated some roller balls and small loose snow sluffs on steep southerly aspects.
Loose snow sluffs on the southerly face of Pk 4940 (south end of Seattle Ridge), viewed from near the Johnson Pass trail head.
|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|
With clearing skies, light winds, some great powder conditions to be had, and some smaller avalanche issues in the top of the snowpack, it might be easy to forget there is a very large and deadly avalanche problem to deal with. The facets from January, that are now buried 3-6′ deep and have been responsible for countless large slab avalanches, continue to be our main concern. It was three days ago two large slabs were remotely triggered from 1,000′ away in the Grandview area and this type of scenario is still possible today and into the weekend. Areas with a shallower snowpack, such as the Summit Lake area, have a higher likelihood for triggering.
Why is this so tricky? It’s because the snowpack can ‘appear generally stable’. In this situation, it’s easy to focus on the current surface instabilities, listed below, and forget about what’s several feet below us. Additionally, triggering these large slab avalanches is becoming more difficult because (1) the thickness of the slab makes it harder to affect the weak layers, and (2) time is allowing the snowpack to slowly adjust to the weight of the slab. Due to the size and deadly nature of a potential large avalanche, along with the lowering changes a person will trigger one, we are in a ‘scary MODERATE’ avalanche hazard.
Current surface instabilities:
Wind slabs: Lingering wind slabs are still possible to trigger on steep wind loaded slopes and in steep rocky terrain. These were formed either in Tuesday night’s 8″ of new snow or hidden below that snow and formed during Sunday’s strong outflow wind event. Either way, even a small wind slab triggered in the wrong place can send us somewhere unforgiving.
Sun Effect: Solar heating in the afternoon may cause loose snow sluffs again today on steep southerly aspects.
Cornices: As always, give cornices a very wide berth and limit exposure under them.
Keep in mind, any one of the above issues on the surface has the potential to ‘step down’ and trigger a large slab. It’s also good to remember there has been very little traffic since the big storm last week. As we venture further into the hills during this clear sky period we need to consider a number of things:
*If you’d rather leave these issues behind, sticking to slopes 30° and less, with nothing steeper above you, is a great way to enjoy the excellent powder.
Large slab that was remotely triggered on Monday, Feb 24th, in the Grandview area.
Yesterday: Cloudy skies gave way to large patches of sunshine in the afternoon. No precipitation was recorded in the past 24-hours. Ridgetop winds were light and easterly with some moderate gusts in the afternoon up to 22mph. Temperatures were generally in the 20’s°F, yet did warm during the daytime sun and hit the mid 30’s°F at mid and lower elevations briefly.
Today: Partly cloudy skies with valley fog in areas, inland skies could be fairly blue. An inversion has setup overnight with cold single digit temperatures in valley bottoms and 20’s°F in the higher terrain. Winds just shifted to the NW this morning and are expected to be light, in the 5-10mph range.
Tomorrow: Mostly sunny skies with some potential for valley fog. The inversion is likely to still be present with valley bottoms in the single digits and warmer air along ridgelines. Ridgetop winds look to remain northwesterly and could kick up to the 10-20mph range. A weak storm front moves in late Saturday and looks to give us another few inches of snow over the weekend.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||27||0||0||80|
|Summit Lake (1400′)||18||0||0||30|
|Alyeska Mid (1700′)||22||0||0||86|
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||26||*N/A||*N/A||*N/A|
*Seattle Ridge anemometer (wind sensor) is heavily rimed and not reporting.
|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: 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.