Lawinenlagebericht

East Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

The chance for very large and unsurvivable avalanches will maintain dangerous avalanche conditions. Ongoing warming temperatures, light precipitation, and isolated fresh drifts will add to the uncertainty. Continue to avoid traveling on or under large open slopes, steep sparsely treed terrain, and areas that received wind drifting in the past week.

Lawinenprobleme

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    3

    Very large, natural avalanches have occurred as recently as Sunday or Monday with more recent avalanches in other zones. Deep persistent avalanches can destroy cars and houses and occur with no warning. An avalanche would be unsurvivable if you were caught while recreating on foot or on a snow machine. Even avalanche professionals with decades of experience have trouble predicting these avalanches and accurately make decisions about them. Continued warm temperatures and rain at low elevations will add another layer of uncertainty to this equation.  A concern with the warming is the chance for large cornices to fall which could, in turn, trigger these destructive avalanches. Avoid slopes with overhead cornices. Make sure not to travel on overhung snow on leeward sides of ridges. 

    The way to stay safe is simple: Avoid traveling in or under large avalanche paths. Avoid leeward slopes 35 degrees and steeper where the wind drifted slabs in the past week. Use extra caution on any steep slope, even around sparse trees. Before you commit to traveling in avalanche terrain, ask yourself, "What's the largest avalanche that this slope can produce, am I willing to take that risk, and is there a safer option?"

    (3/1/2021) A very large avalanche (D3) was triggered by WSDOT highway forecasters on March 1st in a portion of the West Camp path on Rock Mtn. Adjacent sections of this avalanche path ran naturally on Feb 26th. Photo: WSDOT

Avalanche Discussion

The warm temperatures into Friday are concerning since we're only 4 days out from the last known deep slab avalanche. Other weather factors like light precip, rain to 4,500ft, and blowing snow above treeline will complicate conditions. On Wednesday, a party was lucky to walk away uninjured from a cornice fall involvement on the Rooster Comb, adjacent to Stevens Pass Resort. Also on Wednesday, observers west of Lake Wenatchee reported hearing a loud booming noise that they suspected was cornice fall. This is good evidence that more cornices could fall and could trigger a larger avalanche.  Given the bounty of uncertainty already at play with avalanche conditions, forecasters remain concerned about the potential for more very large avalanches. We're in a prolonged period of historically unstable conditions and dealing with a weak layer that is challenging to even seasoned professionals. The deep slab problem continues to pose high consequences and demands conservative terrain and travel choices. 

February 25-26th brought a storm with near to 2" of water equivalent at the Cascade Crest and extreme winds. This came on the heels of an even bigger storm. From the 20-23rd a massive storm brought up to 6" of water equivalent to the mountains near the crest but much less to the Wenatchee Range further east. Numerous deep and very wide avalanches (Many D3-3.5's, some size D4's)  ran on, or around the 22nd in the mountains near the crest, and some deeper slabs were reported from the Wenatchee Range. Similar avalanches have continued into this week. An observer on Wednesday reported widespread very large avalanches in the Chiwaukum range and the Icicle drainage from the most recent cycle. While conditions may be less dangerous in parts of the Wenatchee Mountains, due to less recent snow, the same weak layers can be found and recent avalanches have been triggered on them. In the northern end of the zone, near Holden, the mid-January weak layer is present, though it has produced inconsistent test results. An observer there reported that most avalanches from late February appeared to run on storm interfaces in the upper snowpack.

Recent notable avalanches:

3/1: WSDOT avalanche teams observed a recent (within the past 24hrs) natural D3.5 deep slab from high, north-facing terrain in the Chiwaukum Range. They also triggered an 8ft deep D3 in southeast facing terrain at around 6,000ft off Rock Mountain east of Stevens Pass (the remaining hangfire in West Camp path). Chair Peak at Snoqualmie Pass ran as a D3.5 at some point between Sunday night and Monday morning with a crown 10-15'+ deep. An observer reported numerous very large avalanches near Fortune Peak, just west of this zone.

2/28: A fairly fresh-looking deep persistent slab avalanche from upper elevation terrain was spotted in the Chiwawa drainage. 

2/26-27: A natural D4 avalanche released from Rock Mtn and came just short of Highway 2. A couple of D2.5-3's terrain in Icicle Creek (see photo below).

2/24: A deep persistent slab occurred on a south aspect near Manastash Ridge. 

 

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