Deep Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Unlikely
- Größe
- 2–3
In much of the zone, avalanches are difficult to trigger but not impossible. You may be able to trigger them more easily near Harts Pass or where the weak layer is close to the surface. Deep Persistent Slab avalanches could easily be big enough to kill you and could even be unsurvivable. Limit your exposure to large start zones. Avoid complex and unsupported terrain, shallow, rocky areas, and unsupported slopes.
On March 3rd and 9th, backcountry travelers in the Harts Pass area triggered large to very large avalanches on northerly aspects near treeline. You can find the late January weak layer (facets sandwiched between two crusts) 3-5' below the surface. Snowpack tests can help you identify the layer of concern. Sudden or propagating results have remained consistent during periods when avalanches have become difficult to trigger. East of Washington Pass, the snowpack becomes shallower, and this interface may be nearer to the snow surface.
(3/3/2022)
A very large (D2.5) and widely propagating slab avalanche was triggered by a snowmobile on March 3rd. The crown is estimated at roughly 5ft deep. 6600-6800ft, NE, near Harts Pass
Photo: Drew Lovell