San Francisco Peaks / Kachina Peaks Wilderness

Problemas de aludes

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta montaña
  • Límite del bosque
  • Bajo el límite del bosque

  Probabilidad

  Possible

  Tamaño

  1–2

  Remain aware of the potential for reactive storm or wind slabs. Over the past ~36 hours, winds have been SW, W, NW,  N and NE.  New reactive slabs may be on just about any aspect. Storm slabs are usually softer, and wind slabs are usually firmer. Either way, watch for cracking, collapsing, and shearing of relatively firmer snow over softer snow. The top patrol station has reported relatively light winds with moderate gusts, but backcountry users should still continually assess for the development of new wind slabs. Winds may increase today. 

  Yesterday, near treeline on southwestern aspects, KPAC found stubborn storm slabs that were ~6" thick. Shooting cracks were all short, less than 1m long, and inconsistent.

  Below convexities, on leeward slopes, and at entrances and (cross-loaded) sides of gulleys/chutes, are key locations for wind slab development and hotspots for triggering an avalanche. Pole probe for stiffer snow over softer snow to identify areas with wind slabs. Avoid large loaded pillows of wind-deposited snow. Utilize small and inconsequential test slopes to determine how reactive new slabs are to the weight of a skier or rider. 

  There is a small chance that a human-triggered wind slab avalanche could step down,  triggering a larger avalanche on a persistent weak layer.  See persistent slab problem for more info.

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta montaña
  • Límite del bosque
  • Bajo el límite del bosque

  Probabilidad

  Unlikely

  Tamaño

  1–2

  Currently, easterly aspects above/near treeline are the most suspect for a persistent slab problem. Today, a person's weight will unlikely trigger any persistent slab avalanches. However, a human-triggered wind slab avalanche may step down and trigger a larger persistent slab.

  Snowpit tests and recent avalanches have focused the problem to easterly, northwest, and southwest aspects above and near treeline. The problem may exist in other isolated locations, but no recent observations have confirmed this. Some recent (but minimal) observations suggest the problem is nonexistent on northwesterly, northerly, and northeasterly slopes of Hardcore Ridge and Humphreys Cirque. Between March 19 and 22, a thick and stout melt/freeze crust developed on many sunny and southerly slopes. This m/f crust is now refrozen,  and it is unlikely that a person's weight will penetrate this layer, collapsing any weak layers below. 

  The primary layers of concern are facets above and below the late February melt/freeze crust, topped by a hard slab from the St. Patrick's Day Storm Cycle (3/14-18). The February melt/freeze crust will be approximately 60-80cm below the surface. It will be difficult to distinguish the late February crust on shady/northerly slopes. Use delicate probe work. 

  Last Wednesday (3/20),  a D2 persistent slab avalanche (easterly aspect) was triggered on the skin track out of Humphrey's Cirque (HS-ASr-R1D2-I).  This avalanche was remotely triggered by a collapse that ran towards a rock outcrop and could have gone larger.  Fortunately, no one was caught in this event.  It failed in facets just above the late February melt/freeze crust. See the avalanche details and debrief here.