Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

WSDOT plans to conduct heli-bombing in large avalanche paths above Highway 2 and Stevens Pass on Monday. Stay out of the area to allow them to do their work safely. Check WSDOT website for more.

Warming temperatures will add uncertainty to an already complex snowpack. Very large deep slab avalanches have released naturally, and ski-triggered wind slabs have occurred. Continue to make conservative terrain choices and avoid going on, or underneath steep, wind-loaded slopes while the snowpack adjusts.

Problemi valanghivi

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    3–4

    The uncertainty and unpredictability of deep persistent slab avalanches should determine where and how you travel. We don't know how these could react as temperatures rise to warmer than they've been in well over a month. Avoid going into, or underneath open or sparsely treed terrain with large potential start zones above you. Cornices are huge in some areas, if these break they could trigger big avalanches. Slopes 5,000ft and higher and on east to south to west aspects are the most concern and have recently produced avalanches of D4 in size, over 1,500ft wide and up to 10 feet deep. 

    A persistent weak layer involving facets on or within a crust that was buried in mid-January has plagued the snowpack with lingering instability for over a month. While south, east, and west facing aspects appear to have been especially problematic, we know deep slabs have also run on north and northwest aspects. Unfortunately, this problem isn't going away for a little while, and we shouldn't be surprised to hear about more of these monsters in the next few days. Continue to let the deep new snow settle, and tread carefully around these sleeping dragons.

    A deep persistent slab avalanche ran naturally at around 10:30pm on February 26th in a path known as West Camp off Rock Mountain above Highway 2 east of Stevens Pass. Southeast to Southwest aspects with the crown running from around 6,200ft to 5,400ft.

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2

    Wind slabs could remain reactive to human triggering on Monday. Even outside of wind affected areas, you could trigger avalanches in the recent storm snow. A sun crust from the middle of the week was responsible for a close call with a skier triggered avalanche. If trigger an avalanche in the upper foot or two of snow, it could be large or even step down to become a very deep and destructive avalanche. With wind slabs, storm slabs, and the potential for deep slab avalanches, you should avoid large avalanche paths, especially at mid and upper elevations. Avoid wind-loaded, leeward slopes 35 degrees and steeper.  Below treeline, stick to wind-sheltered slopes and well-supported features. 

    (2/26/2021) This avalanche was about 20" deep x 200ft wide, and ran on the suncrust from February 24th. It caught a skier who was then partially buried, and lost some ski gear. Southeast aspect at 5150ft in the Polaris Boundary Glade.

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    The warm temperatures may create wet loose avalanches on all aspects below treeline on Monday. If the sun is out where you are, expect these to happen on steep slopes that face toward the sun most readily. Moist, sticky snow and rollerballs are good indicators that the snow is capable of producing these. Get off of steep slopes at lower elevations by mid-afternoon to avoid this problem.

    Rollerballs like this are signs you could trigger loose wet avalanches on steep slopes nearby.

Avalanche Discussion

WSDOT plans to conduct heli-bombing in large avalanche paths above Highway 2 and Stevens Pass on Monday. Stay out of the area to allow them to do their work safely. Check WSDOT website for more.

We're in for a fairly significant warm-up on Monday. This adds uncertainty to a snowpack still settling with lots of recent storm snow. Stay observant, and keep your eyes peeled for signs of instability.

A massive avalanche (D4) ran naturally out of a path on Rock Mountain called West Camp on Friday night at around 10:30pm. The powder cloud took out power lines and dusted Highway 2 with tree debris. This avalanche started on Southeast to southwest aspects at around 6,200ft and took out substantial amount of forested trim line around the runout zone (see photos below). A partial burial occurred on Friday just outside of the Stevens Pass Ski Area boundary. This avalanche (D2) was 18"-20" deep, about 200' wide, and ran on a steep southeast aspect at 5,150ft. We are glad the person is ok. On Saturday Stevens Pass Ski Patrol inspected this avalanche and found that it ran on preserved stellar crystals over the sun crust from 2/25, and snowpack tests continued to indicate the potential to create avalanches. 

From the 20-23rd, the Schmidt Haus station picked up a whopping 6" of water equivalent. Numerous very large and destructive avalanches ran during a period of High to Extreme avalanche danger on the 21-23rd:

D3 sized natural avalanches on a ESE aspect at 5,200ft near Skyline Lake (in the Moonlight area). These were at least 7ft deep, knocked down trees, and may have run on the 22nd.

In the Scenic area, guides reported size D3 natural avalanches running on the mid-January weak layer 3-10ft deep on W-N aspects.

Natural avalanches ran on SE and SW aspects of the Tunnel Creek area to D2.5. WSDOT triggered a very large size D3 in one of the Old Faithful paths on a SW aspect below treeline. 

Natural avalanches to size D3 on a SE aspect of Lichtenberg Mtn as well as a D4 sized avalanche on a SE aspect of Rock Mountain in Schilling's creek. This avalanche broke many mature trees and deposited debris 40 feet high near Highway 2.  

Regioni coperte