Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Wed
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
Open full map
Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Tuesday should be a warm, and dangerous day for upper elevation terrain. Wet loose slides are expected to grow large with daytime warming and could step down to older, deeply buried crusts. You could trigger large persistent slab avalanches on shaded slopes above 5,500ft.

Problemi valanghivi

  • Loose Wet

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

    We're in the middle of a warming trend with the snow level continuing to creep up the mountainsides. Wet loose avalanches should continue to grow larger as the day warms up, influenced by light rain then sunshine later. Signs of wet loose avalanche activity are rollerballs, and fresh fan-shaped avalanches with chunky looking debris.

    Stay off of, and out from underneath very steep slopes. Be especially careful of going underneath larger steep slopes where slides could pack more of a punch and hit you from above. At upper elevations, wet slides could entrain lots of snow and become large avalanches. They could also pull out wider slab avalanches on deeper layers. Above 5,500ft, NW-NE aspects harbor weaker, faceted grains over a crust from early March. This layer could be down close to 3ft deep in some areas, and any avalanche that runs on it would be very large. Tuesday is a good day to let the warm temperatures do their thing and stay away from steeper slopes while the snowpack slowly adjusts.

    Example loose wet avalanches below treeline.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    We've slowly been adding more and more snow to a buried persistent weak layer. A 2ft deep slab avalanche was triggered on Sunday near Mt Fernow on a NE aspect at 5,800ft in a wind loaded gully. An observer reported whumphing collapses at 6,200ft in a wind loaded location near Mission Ridge. These are all direct signs of instability relating to a layer of faceted grains overlying a crust buried in early March. However, many observers report a lack of whumphing collapses, but still found the weak structure in profiles. This is insight is unsettling, because it means you may not get direct feedback before triggering a deeper slide.

    Any avalanche that runs on the crust could be a couple feet deep and could be fairly wide. Avalanches could be triggered from a distance, or below.  Plan to stay off of large and steep, shaded slopes above 5,500ft, especially if they appear to have been loaded by the wind in recent days. Travel on lower angled slopes, without large steep features above you.

    Example recent slab avalanche from the East South zone.

    Photo: Andrew Kiefer

Avalanche Discussion

Monday's warm front dropped about 0.5" of SWE at Sasse Ridge Snotel site and 6" of new snow. Higher elevation locations near the crest have likely received closer to a foot of new snow since the 20th. Numerous storm slabs (some large at Snoqualmie) and wet loose avalanches were reported from neighboring Snoqualmie and Stevens Passes on Monday. Temperatures are expected to continue to warm quite rapidly on Tuesday, with light rain possible near the crest.

Observers have been documenting weaker, faceted grains and/or surface hoar overlying a crust from early March on W-N-E aspects from Stemilt Basin to Icicle Creek, and other areas to the north and south. Above 5,500ft, these slopes harbor weaker, faceted grains over a crust from early March. This layer could be down 2ft deep or greater in some areas. On Sunday, skiers triggered an avalanche on it near Mt Fernow that was 2ft deep and 40ft wide. Observers in the Chiwaukum range also found the weak layer above 5,000ft and reported significant wind loading on Saturday. On Friday, I found the March 8th facets in the White Pine drainage. A vague observation of large collapses in the Teanaway also came in from Saturday (unknown details). 

Regioni coperte