Rain on snow is expected below 1500’ and will be adding significant stress to the snowpack in the mid and lower elevation zones. A weak interface (facets and buried surface hoar sitting on a crust) is underneath yesterday’s 20” of storm snow. Add today’s rain and this is a perfect recipe for wet slabs. Natural and human triggered wet slabs 2-3 feet deep are likely on slopes steeper than 30 degrees including both large and small terrain features. Triggering this kind of avalanche will be impossible to escape and could be unsurvivable. It will be very important to avoid terrain traps and being near the runout of larger slopes.
Remote triggered avalanche on Tincan yesterday. This is a good example of a small terrain feature that could be releasing naturally if rain saturates the snowpack today. Photo credit: Matti Silta
Yesterday 20” of new snow was observed in Turnagain Pass and today another 12-20” of heavy snow is expected in the upper elevations above 1500’. Natural slabs 3-4 feet deep will be likely today and human triggered avalanche very likely. Strong Easterly winds in the 40’s with gusts in 90’s are also anticipated. All 6 Red Flag warning signs were observed yesterday at Turnagain Pass. This includes a remote triggered avalanche on Tincan, large shooting cracks, collapsing “whumpfing sounds”, rapid loading due to heavy snow and strong winds, and warming temperatures. All of this new snow has fallen on surface hoar and near-surface facets and slabs will be easy to trigger. Below 2000’ these weak layers are sitting on a slick crust and a slab could easily catch you by surprise, even in the protected trees of Tincan or getting your snowmachine stuck under a small steep terrain feature. Strong winds today could trigger a large natural avalanche that could run down to valley bottoms. Maintaining a safe distance from the runout zones of all larger slide paths including Repeat Offender will be important. Remote triggering an avalanche from below or above is also possible. Basically today is a good day to avoid the mountains around Turnagain Pass. In fact this is a good day to head to Hatcher Pass and practice your avalanche rescue skills. Click HERE for details about the free clinic.
A very large shooting crack on a wind loaded terrain feature was intentially triggered by a snowmachine near the motorized lot yesterday. Windloading has created variable slab depths. Slabs could be as deep as 4-5′ on leeward features.
Natural and human triggered avalanches today could step down to deeper layers of the snowpack producing a very large avalanche depending on the size of the slope. A layer of buried surface hoar from the New Year’s holiday has been showing propagation potential in test pits including a pit dug yesterday at 2000′ on Tincan by an avalanche course. In addition, a Deep Persistent Slab problem remains a concern in the upper elevations above 3000’, and serves as one of the many reason to avoid avalanche terrain today.
Yesterday Center Ridge Snotel recorded 0.6 € Snow Water Equivalent (SWE) at 1700′ and the RWIS DOT Wx station recorded (1.13 € SWE) at 1000′. Field observations confirmed about 20 € of new snow since Thursday when the storm began. Sunburst Wx station showed strong Easterly winds all day averaging in the 40’s mph with a gust to 92mph last night. Rain/snow line started out at sea level yesterday morning and increased to just below 1000′ this morning.
Today there is .95 € rain (SWE) expected, this translates to another 12-20 € of snow in the upper elevations. Unfortunately rain/snow line will continue to rise to 1500′ possibly higher. Strong winds will continue to blow from the East and average in the 40’s mph with gust in the 80-90’s mph. Peak intensity and warmest temperatures should begin later morning through 8pm this evening.
Tomorrow afternoon another front is expected. There’s some uncertainty as to how much precipitation and wind, but temperatures are expected to remain warm.
*RWIS DOT weather station at 1000′ on Turnagain Pass recorded 1.13 € SWE. This weather station is located further North where precipitation is often heavier than then further South in Turnagain Pass.
**Seattle Ridge weather station is covered with rime and stopped recording wind data at 4pm yesterday (1/12/18)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||32||*4||*0.6||57|
|Summit Lake (1400′)||34||1||0.1||15|
|Alyeska Mid (1700′)||32||4||0.92||48|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||26||**SE||**24||**46|
|01/22/20||Turnagain||Observation: Sunburst||Adrian Beebee|
|01/22/20||Turnagain||Observation: Sunburst||Ryan Van Luit Forecaster|
|01/22/20||Turnagain||Observation: Seattle Ridge||W Wagner Forecaster|
|01/22/20||Turnagain||Observation: Tincan||Allen Dahl|
|01/21/20||Turnagain||Observation: Tincan||Eric Roberts|
|01/20/20||Turnagain||Observation: Eddies||H. Thamm B. Edwards|
|01/20/20||Turnagain||Observation: Eddies||Andy Moderow|
|01/19/20||Turnagain||Avalanche: south facing aspect on 3800ft bump just northeast of 4940||Anonymous|
|01/19/20||Turnagain||Avalanche: Cornbiscuit & Magnum||Allen Dahl|
|01/19/20||Turnagain||Observation: Eddie’s||Kakiko Ramos-Leon|
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.