After almost 2 weeks of sunny skies and high pressure, clouds and a warm East wind have moved in. The big news is how last night’s cloud cover has trapped yesterday’s daytime heat. This morning temperatures are 10-15 degrees F warmer than they have been during the past week and we are expecting a very limited, to no, re-freeze of the snow surface. The only thing that would help the re-freeze would be the increased winds, but they are only blowing 10-20mph and bringing in warm temperatures, so the wind may not keep the snow as cool as one would expect. That said, with a lack of re-freeze it will not take much daytime warming, or direct sunshine to initiate wet slab or wet loose avalanches.
WET SLAB, WET LOOSE, GLIDE AVALANCHES and CORNICE FALLS:
Although these are different characters of avalanches, they are all occuring together as the mountains fall apart with the springtime melt down. Widespread natural wet avalanche activity has already been seen on Southerly aspects, but the more shaded Westerly through Northeast aspects have yet to fall apart. This could happen this weekend as cloud cover has enhanced warming on all aspects. If choosing a day in the mountians this weekend be aware natural avalanches are possible and could become likely by Sunday. Things to keep in mind:
Recent avalanche on Seattle Ridge (released Friday, April 21st)
Cloud cover over Tincan Ridge – trapping in the daytime heat overnight
*For the complete snow science geek out there – make sure and check out the Beaded Stream snow temperature array at the top of treeline on Tincan. This instrument measures ground, snow and air temperature vertically: Starting from 15cm (6″) below the ground, there is a cable extending 4meters (12′) upward that has a temperatures sensor every 15cm. The warmup of the whole snowpack can be seen – right now at this location (2,350′ in a flat area) the pack is almost isothermal , which means all the same temperaure at 32F. This is important because it indicates the potential for natural wet avalanches to begin on shady Northerly aspects.
Although technically glide avalanches are a different beast than wet avalanches, they were lumped into the discussion above because how we deal with them now is similar to wet avalanches – simply avoidance. Avoid being under glide cracks – there are several cracks along Seattle Ridge, Tincan Ridge and many other slopes in the region. Each day we have seen 1-2 new glide releases (The photo above of Seattle Ridge being the last known glide release). The number of releases should increase with the warm weather.
Upper elevation Northerly aspects should be warmer today. The cold dry snow surface could be giving way to a moist and wet snow surface, if it didn’t already overnight. With the added warmth of the pack in these shaded zones, increased stress on underlying weak layers will be occurring. There are several buried persistent weak layers in the snowpack; ranging from buried surface hoar 2-6′ deep, mid-pack facets and facets near the ground. Shallow snowpack zones such as the Summit Lake area harbor depth hoar near the ground. As the snowpack warms up, these weak layers could re-activate and triggering a large slab avalanche is possible. This is a low probability, high consequence problem.
Keep these points in mind:
Cloudy skies (yes, cloudy for the first time in practically 2 weeks!) were over the region yesterday. Winds moved in with the clouds and over the past 24-hours ridgetops have been blowing 10-20mph with gusts in the 30’smph from the East. Temperatures warmed up to 50F at sea level, ~45F at 2,000′ and 30-35F along ridgetops yesterday. Overnight only a slight drop in temperature has been seen and all elevations.
Expect a cloudy, breezy and warm day today as we are on the Northern edge of a large trough digging in the Gulf to our South. Ridgetop winds should remain in the 10-20mph from the East while temperatures continue to be near 50F in the parking lots and 30-35F along ridgetops. There is a chance for a rain drop or two tonight, but most of the precipitation will be to the South near Seward.
For Sunday, we could see light rain in places as the frontal boundary associated with the Gulf trough sends some moisture our way. In general however, the forecast is for cloudy skies, warm temperatures and breezy winds.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||42||0||0||60|
|Summit Lake (1400′)||41||0||0||19|
|Alyeska Mid (1700′)||40||0||0||54|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||33||SE||30||13|
|01/16/21||Turnagain||Avalanche: Tincan Trees||A Schauer Forecaster|
|01/15/21||Turnagain||Observation: Sunburst||Schauer/ Wunnicke Forecaster|
|01/13/21||Turnagain||Observation: Tincan||Johnston-Bloom / Moderow Forecaster|
|01/13/21||Turnagain||Observation: Center Ridge Meadows||Alaska Avalanche School Rec Level 1 Roberts|
|01/12/21||Turnagain||Avalanche: Seattle Ridge/Center Ridge||A Schauer Forecaster|
|01/11/21||Turnagain||Observation: Tincan Trees||Schauer/ Roberts Forecaster|
|01/10/21||Turnagain||Observation: Center Ridge Meadows||Alaska Avalanche School Pro 1 Course Latosuo|
|01/10/21||Turnagain||Avalanche: Tincan trees||Anonymous|
|01/09/21||Turnagain||Observation: Johnson Pass||Anonymous|
|01/08/21||Turnagain||Observation: Sunburst meadow between Hemlocks||Anonymous|
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.