Lawinenlagebericht

East Slopes North

Northwest Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

Winds and a trickle in of new snow may have created shallow windslabs at upper elevations. Chances are low for triggering hard persistent slabs, but they are still possible. Be careful treading into complex or unsupported terrain at mid and upper elevations on the north half of the compass, especially with larger triggers such as snowmobiles or the combined weight of a group of people. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2

    Snowpack tests have indicated that large persistent slab avalanches are still possible on shaded slopes above 5,000ft. Consider avoiding shallow, rocky, or very steep unsupported slopes. North and east aspects without supportable crusts near the surface may be the most likely areas to trigger a slab. Look for safe locations to stop and regroup, creating a buffer of distance between you, and larger start zones.  Keep in mind potential for cornices to fail, these could trigger larger slab avalanches on unsuspecting travelers below. Larger triggers such as snowmobiles or a group of people may trigger one of these slabs of older, stiffened snow.

    "Red flag" indicators of persistent slabs are whumphing collapses and snowpack tests that pop or drop suddenly. Avoidance of slopes where we know the recipe exists for these avalanches is really the only way to be sure to stay safe, even though chances of triggering one of these may be low. You can dig down and find the late-January weak layers 1-2 feet below the surface.  In many areas, this layer is a combination of weak sugar-like facets sandwiched between two crusts.Sometimes you'll find weaker snow or old surface hoar above the upper crust. The weak layers are deepest near and west of the Cascade crest and in wind deposited zones. In the eastern part of the zone and in wind scoured areas, the crusts may be found near the surface.

    (2/5/2022)

    A skier triggered avalanche near Maple Pass. Three people were caught, one was carried over 400ft with no injuries. E, 6,600ft

    Photo: NWAC public obs

Avalanche Discussion

Winds should ease a bit on Friday, and it should generally be a nice day in the mountains with a mix of sun and clouds. Observers have been finding up to 6" near and west of the Cascade crest.  Gusty winds and a trickle in of new snow may have created drifts near ridgelines and in open-exposed alpine terrain. Be on the lookout for shallow wind slabs as you gain elevation, and check for cracking in the snow. Test slopes can be a good way to evaluate shallow, new snow instabilities, although it is the persistent slab that really dictates where one can safely travel in the zone. A strong frontal system should arrive by Saturday afternoon, and we expect the avalanche danger to increase substantially overnight into Sunday.

During the week observers have been targeting the late January weak layer. The one thing in common is that most tests produced sudden collapse results. Even on Thursday, observers found sudden collapse test results with moderate compression tests, and an extended column test propagated with moderate force on an ENE aspect at 5,700ft near Liberty Bell. On Wednesday observers found sudden collapse test results with compression tests in Fisher Creek. In general, shaded, northerly aspects are still showing the most potential for human triggered avalanches where the crust-facet sandwich is most defined and weakest. The most recent natural avalanche on this layer was a D1.5 on a rocky, unsupported east aspect, near treeline on Porcupine Peak (see photo). Last week, observers noted a cornice fall that triggered a large wind slab avalanche in rocky north-facing terrain. On  February 5th, a notable avalanche was triggered near Maple Pass on an east aspect, near treeline. The slide likely occurred on the late January PWL and involved 3 people, carrying one over 400ft. Widespread whumpfing, rolling collapses, and remote triggering of avalanches were all common last week, though these direct signs of instability have become less frequent in recent days. The recent warm temperatures appear to have helped the snowpack and late January weak layer gain strength. 

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