Wet Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 2–3.5
Today will be day four without a solid overnight refreeze. Large amounts of moisture is moving through the snowpack and pooling around existing weak layers and crusts. As these layers lose strength, large wet slab avalanches are possible. For the past few days we have seen natural wet slabs release every day. Some of these slabs have reached large D3+ size.
Wet slabs are difficult to forecast exact timing. Small changes across a zone like cloud cover, wind speed, or just a few degrees of slope angle changing the amount of incoming sun can make slopes avalanche naturally or not. Today we add rain and snow to the equation. With the rain comes increased water to the snowpack and potential for warming from “greenhousing” from low elevation clouds. These two could tip us into a very active day for avalanches. Conversely, if the cloud cover remains high, temps drop, and the wind increases, it could be a calmer day for avalanches.
A few inches of snow is likely at upper elevation today. This will not be enough to effectively cool the snowpack. The heat and water from the past few days will still be moving through the snowpack and pooling around weak layers. In short, there are multiple variables affecting this avalanche problem today. When in doubt, keep it simple and manage the problem through terrain selection.
If you do decide to test one of these slopes with your bodyweight or snowmobile, you are likely to trigger an avalanche. Natural cornice failure is a likely trigger for avalanches as well.
There is no good snowpit test for assessing wet slab potential. A lack of results in pit tests doesn't mean avalanches are unlikely. Look for wet saturated snow and buried weak layers. If you see these, avoid slopes over 30 degrees.
Other wet snow problems you may encounter today:
- Wet Loose: Expect wet loose avalanches on all aspects today. By now most sun facing slopes have already gone through a wet loose avalanche cycle. This cycle will continue around the compass onto north aspects that do not receive sun. The size of all wet loose avalanches will be dictated by the size of the slope and amount of snow available for the avalanche to entrain on its way down.
- Glide: New glide cracks are opening in the Bitterroot, and we’ve seen evidence of recent glide avalanches. Glide avalanches are incredibly difficult to predict. The time between when a crack opens and when an avalanche occurs can be measured in minutes or weeks. A common trend is glide avalanches failing on days when liquid water is actively moving through the snowpack (like today).
A natural D2 wet slab avalanche which occurred on 2026-03-20 on a NE aspect at 7200 feet.
Photo: Nata de Leeuw