Wet Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1.5–2.5
Yesterday temperatures in the mountains were well above freezing. Overnight lows have not been cold enough to refreeze the snow for multiple days now. As snow melts and water begins moving its way through the snowpack, buried weak layers become destabilized. During a wet slab cycle you may see avalanches on layers that have been previously unreactive in the snowpack. At this point in spring the sun travels high enough in the sky that northerly slopes are impacted by solar warming midday. Wet loose avalanches may occur in isolated pockets of terrain on more northern aspects up high. Wet hazard forms and behaves very differently than the mid-winter dry slab avalanches we see through most of our season.
Wet slabs avalanches are inherently challenging to forecast for. Today we have the big factors at work; thawing daytime temperatures, no overnight refreeze for multiple days, layering still present in the snowpack. Because these avalanches are difficult to predict, build large margins into your travel plan and be prepared to back off, and potentially out of the mountains, as the sun heats things up and gets water moving through the snow.
Cornice Falls: The continued warm, sunny weather is destabilizing the large cornices that have built up over the season. It is possible to trigger failure by stepping out onto these features, or they may fail naturally. A big cornice fall has the potential to trigger a large, destructive avalanche on the buried weak layers that persist near the base of the snowpack. While this is unlikely, a recent natural slide on The Wedge demonstrates that this risk still exists.
An example of what might be seen today in the Greys - This wet slab avalanche occurred earlier this season in the southern Tetons during a similar weather pattern.
Photo: Bridger-Teton Avalanche Center