For the past week, observations have been limited due to elevated avalanche danger and poor visibility. A brief window into the alpine yesterday confirmed our suspicions that we are still within a very active natural wet avalanche cycle. Temperatures were the warmest we’ve seen all spring at ridge top locations yesterday and the mountains surrounding Turnagain Pass appear to be going thru a spring ‘shed-cycle’ of sorts. Large natural avalanches are failing on all aspects, particularly in the mid-elevation band below about 2,500’ and showing potential to propagate across wide distances. What hasn’t avalanched yet will be stressed by another half inch of water weight today. These could fail either as storm slabs (2-4’ deep) or step down into weaker snow near the ground (4-6+’ deep). At this point it doesn’t really matter what the weak layer because this is not an avalanche problem to mess with or try and out-smart. The snowpack will remain touchy and with natural avalanches likely again today, travel in avalanche terrain is not recommended. Avoidance will be your best and only tactic until this warm and wet pattern of storms subsides and we can take stock of what is left of our snowpack.
Nearly wall to wall avalanching on Seattle ridge (lookers left of the common snowmachine up-track) “Repeat offender” path as viewed from the Seward Highway.
WIND SLABS and CORNICES:
Strong winds last night combined with more snow will act to create large wind slabs and cornices on leeward slopes in the upper elevations. With temperatures rising to above freezing in the alpine these may release naturally and could entrain enough snow to run quite far. Any additional wind and precipitation today will add further stress.
How much load is on the old weak surface from March? Storm totals (March 27 – 6am April 6th):
Turnagain Pass: 4.7″ of H2O, 48+” of snow at upper elevations
Girdwood Valley: 5.5″ of H2O, 55+” of snow at upper elevations
Summit Lake: 1.6″ of H2O, 15+” of snow at upper elevations
Widespread avalanching on Eddie’s lower rolls as seen from the RWIS web cam during a brief period of clearing yesterday afternoon.
The balance has been tipped and avalanches this week have been observed stepping down into old weak layers. Dirty debris in places is indicative that some avalanches were running to the ground. Prior to this storm cycle the snowpack consisted of many weak layers of facets and buried surface hoar. We may continue to see avalanches today breaking in the mid-pack or near the ground, with crown depths over 6′ and running the entire length of a slide path. Again, avoidance is key with this problem as a persistent slab avalanche in our current snowpack is not a survivable event.
Recent full-depth avalanche on Seattle ridge (across from Sunburst) stripping out the entirety of our snowpack.
Daylight hours yesterday provided a brief reprieve from the deluge of wet, cloudy weather (enough to view the alpine) though we still ended the 24-hour period with .5 – .7 € of water and likely another 5 €“ 10 € of snow above the freezing line (~2,000′). Temperatures were WARM with the Center ridge SNOTEL topping out at 44 degrees (1,880′) and Sunburst weather station (3,800′) reaching a high of 30 degrees. Overnight, another front impacted our area with temperatures dipping slightly and east winds increasing quite dramatically around 6pm with Sunburst measuring a 7-hour period of sustained winds in the 40’s and gusting into the 70’s mph from the east.
You guessed it, another storm day on tap for our region today! Temps should cool slightly (mid-30’s at 1,000′) from yesterday bringing the rain/ snow line back down somewhere closer to 1,500′. Expect another .5 € of water and winds again from the east in the 20 €“ 45mph range at ridge top level.
Looking out toward the weekend we may see a break in this overall pattern and see some clearing with slightly cooler temperatures by Saturday and Sunday.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||40||0||.7||79|
|Summit Lake (1400′)||38||0||.1||27|
|Alyeska Mid (1700′)||35||0||.5||72|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||30||E||32*||75*|
*Winds reporting since 3pm
|12/10/19||Turnagain||Avalanche: Tincan and Sunburst from the air||CNFAIC Staff|
|12/10/19||Turnagain||Observation: Tincan||Nancy Pfeiffer|
|12/08/19||Turnagain||Avalanche: Tincan||Ryan Van Luit Forecaster|
|12/06/19||Turnagain||Avalanche: Sunburst||Billy Finley|
|12/04/19||Turnagain||Observation: Sunburst||A.Johnston-Bloom/ W.Wagner/ R.Van Luit Forecaster|
|12/03/19||Turnagain||Observation: Hippy Bowl||Nick Langowski|
|12/01/19||Turnagain||Observation: Tincan, All elevations||Eric Roberts|
|12/01/19||Turnagain||Observation: Tincan||Andy Moderow|
|11/30/19||Turnagain||Observation: Tincan Treeline Plateau/ Common Bowl/ Ridge||Eric Roberts|
|11/29/19||Turnagain||Observation: Sunburst Ob #2||Aleph Johnston-Bloom 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
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