West Slopes North

Lawinenprobleme

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  1.5–2.5

  Dangerous avalanche conditions will exist on Saturday. It's likely that you could trigger a large avalanche that could kill you, with snow and wind actively loading more snow throughout the day. You're most likely to trigger an avalanche, which will probably be larger, in a thicker wind-loaded pocket, but avalanches could happen on any steep slopes given the new snowfall amounts we're receiving. 

  This week was riddled with human-triggered slab avalanches and avalanche involvements, and we only expect an uptick for Saturday:

  •  On Thursday, skiers in the Baker backcountry remotely triggered an avalanche on the east face of Mt Herman in the Baker backcountry. They were only midway on the slope, and the avalanche propagated several hundred feet uphill of them and that much downhill as well. No one was caught.
  • On Friday a party of 2 skiers triggered a slab avalanche in the East Gully of Mt Herman in the Baker backcountry, right next to the previous day's avalanche. One person was caught, carried, and partially buried. 
  • Numerous human-triggered D2 (large) avalanches were reported in the Baker backcountry on the Arm and in Bagley Basin on Friday (OBSERVATION and media photos).
  • A few snowmobile-triggered avalanches were reported in Canyon Creek, some of which failed on newer wind slabs, but at least one failed deeper on the persistent layer (see Persistent Slab Problem below).

  Several storm layers stacked up this week, and there's a chance an avalanche could fail at any one of these older interfaces. For Saturday, plan on avoiding all slopes greater than 30°. If you notice natural avalanches, or have any doubt, steer around lower-angle terrain beneath large avalanche paths, where an avalanche could run and stop, as well. 

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  2–3

  Sledders in Canyon Creek on Friday triggered avalanches that are failing as deep as the persistent weak layer, which is buried about two feet below the snow surface. Skiers in the Twin Sisters area were remotely triggering avalanches on a persistent layer on Thursday. Many slab avalanches were triggered in the Baker backcountry in recent days, and very few if any failed on the persistent layer. We are less inclined to believe the weakness exists there,although it's not out of the question.

  The culprit is a thin layer of surface hoar and possibly some small, weak, facets, buried just above the obvious March 4 crust. The layer exists on shady aspects, including east-facing. You won't be able to tell where this layer does and doesn't exist unless you dig down to it and complete some pit tests, but even if you do, this isn't a guarantee the weakness doesn't exist nearby. We're not quite sure of the spread of the problem throughout the zone, although we know it varies from one area to the next.  

  If avalanches occur on this layer, especially with more wind-affected snow on top, they will be larger and could propagate further and in surprising ways. Given the pattern we've seen so far, your best options are to avoid steep slopes on east through northwest aspects at mid and upper elevations if you want to avoid triggering a large or very large avalanche that could be unsurvivable.