A warm and very intense storm is arriving as we speak. The rain/snow line should rise to 2,000′ and 10-16″ of snow is forecast above 2,500′. Associated with the new snow will be very strong Easterly ridgetop winds. This is a classic storm snow avalanche problem. With wind likely to affect most locations above 2,500′, naturally occurring wind slab avalanches are expected on many leeward slopes. These are expected to run into the 2,000′ elevation zone, where it may be raining, and possibly further.
Not only is a foot or more of new snow falling in 12 hours, accompanied by strong winds, a concern in itself, it is falling on a very weak pre-existing surface. Widespread surface hoar up to the ridgetops – 2cm (3/4″) in size, which is significant – was just starting to be covered up intact and upright yesterday. Hence, bonding between the new snow and old snow will be poor with this persistent weak layer sandwiched in between. As snow piles up and becomes cohesive with the warm temperatures, slabs will have potential for wide propagation.
Slab depths for today’s expected new snow will be in the 1-2′ range. These are not exceedingly thick slabs for a HIGH danger day, but the expected rapid loading on a weak layer of surface hoar should produce widespread avalanche activity with dense debris. Steering clear of avalanche terrain while it continues to snow and blow is recommended.
Rain on an old battered and frozen snowpack is expected from ~2,000′ and below. Above this, around 2,500′, 6-8″ of wet snow is likely to fall on a stout and well developed crust. Naturally occurring wet loose avalanches composed of the new wet snow are likely to run on steep slopes. Areas that are in this zone are the East face of Seattle Ridge and Magnum’s West face.
Yesterday, skies were mostly cloudy with light snow beginning to fall in the early afternoon as the leading edge of today’s low pressure system pushed in. The rain/snow line rose to 500′ by the evening. Don’t forget about the table below for additional past 24-hour weather details!
Overnight we have seen ~.3-.5 of rain below ~1000 in the Girdwood Valley and Portage area with 4″ of wet snow at the Center Ridge (Turnagain Pass) SNOTEL site at 1880′. Ridgetop Easterly winds are on the rise from the teens to the 30’smph with gusts to the 50’s. Temperatures are steadily climbing (unfortunately) with 1,000′ temperatures in the mid 30’sF.
Today, we will see temperatures rise another few degrees F with the rain/snow line creeping to 2,000′. Between 1 and 1.5″ of water equivalent is expected by this evening at Turnagain Pass with 10-15″ of snow at the above treeline elevations. Ridgetop Easterly winds are forecast to be in the 30-40mph range with stronger gusts.
Monday, precipitation, Easterly wind and even temperature should decrease slightly. Models are showing 1 – 1.5″ of rain below 1,500′ and another 10-16″ of snow above.
A series of low pressure systems will continue to move through the Northern Gulf with additional cooler temperatures and additional snow (hopefully to sea level). Stay tuned.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||31||4||0.4||22|
|Summit Lake (1400′)||28||0||0||4|
|Alyeska Mid (1700′)||32||2||0.6||15|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||27||SE||15||31|
|04/21/21||Turnagain||Observation: Sunburst||Schauer/ Behney Forecaster|
|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|
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.