Persistent Slabs
N
NE
E
SE
S
SW
W
NW
- Alpine
- Treeline
- Below treeline
- Likelihood
- Unlikely
- Size
- 1.5–2.5
Weak layers of snow are buried 2-4 feet deep on middle and upper-elevation shady slopes. Larger triggers, such as groups, snowmobiles, or falling cornices, will increase the odds of impacting these weak layers. Choosing terrain that minimizes consequences and remaining vigilant if traveling in complex avalanche terrain continues to be a good call. This problem is most commonly found on slopes with the following characteristics:
- Very steep: slopes steeper than about 35 degrees.
- Rocky: slopes with variable snow cover due to the roughness of the terrain.
- Wind-affected: slopes where winds produce variable snow depths.
ADDITIONAL DISCUSSION
The above slopes are conveniently also where you are most likely to find:
- Loose Snow Avalanches: these may be encountered if you are playing in sunny, steep, rocky terrain. As temperatures climb above freezing, it will be possible to trigger loose snow slides large enough to knock you off of your feet. Though they start small, these avalanches can entrain more snow as they travel downslope.
- Isolated Wind Slabs: a few stubborn slabs of new snow may remain in very steep (>35°), wind-loaded starting zones above 9,000’. Easterly winds are an unusual wind direction that may have formed slabs in terrain that does not typically see loading. These slabs may also become more sensitive as the day warms up.