Flathead Range & Glacier NP

Lawinenprobleme

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1–2

  Southwest winds redistributed mid-week modest snowfall into thin slabs. Winds have tapered but may rise to the speed capable of transporting snow later today.  You can find drifted snow near ridgelines or prominent terrain features where the wind decelerates and deposits snow.

  Slabs will be more stubborn to trigger than the past couple of days. You can identify these features by denser snow which keeps you or your machine from sinking more than a few inches. Dune-shaped features or a scalloped surface indicate that the wind has been at work. 

  Windward terrain or areas sheltered from recent wind offer slopes without a wind slab problem. If you plan on riding steep leeward terrain, choose runouts free of surface obstacles which can magnify the consequences of a slide or terrain traps where the snow can pile up deep.  

   

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Unlikely

  Größe

  1–3

  A small collapse felt by a skier near the continental divide is the most recent sign of instability we received from weak layers formed in mid-January. This persistent slab problem hasn't been particularly talkative of late. To get to know it better, we must be active listeners and ask the right questions. Digging a pit is the best way to "break the ice," so to speak. Observers continue to find weak structures throughout the advisory area. This appears to be most prevalent on shaded aspects at middle and upper elevations in the Swan Range, Flathead Range, and Southern Glacier Park.  

  In the Swan Range, the primary concern is a layer of surface hoar capped by a hard crust formed during the MLK weekend. This layer is buried 2-4 feet below the snow surface and has repeatedly produced propagating results in Extended Column Tests and Propagation Saw Tests. In some areas, more recently buried surface hoar layers may or may not be more reactive.

  In the Flathead Range and Southern Glacier Park, this interface is buried 1-2 feet below the snow surface and consists of well-developed facets above and below the crust. Propagating results have been less frequent in this zone, but the structure certainly isn't confidence-inspiring. In a recent trip to the Middle Fork corridor, Cam described these layers as "sitting ducks waiting for a slab."

  Continue to choose lower-angle terrain free of overhead hazards and convexities where you find these layers. Slopes with clean runouts are an excellent way to build a margin of safety into your day. Keep in mind that even a small slide has the potential to step down to buried weak layers and trigger a much larger slide.