Wet Slabs
- Alpin
- Limite forestière
- Sous la limite forestière
- Probabilité
- Possible
- Taille
- 1.5–2.5
Yesterday temperatures in the Tetons reached into the 40s above 10,000 ft. For multiple days it has not cooled enough overnight to refreeze the snow. These conditions cause melt water to begin moving its way through the snowpack, destabilizing buried weak layers and lubricating sliding surfaces. During a wet slab cycle you may see avalanches on layers that have been previously unreactive. 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 hazards form and behave very differently than the mid-winter dry slab avalanches we see through most of our season.
Wet slab avalanches are inherently challenging to forecast for. Today we have the main drivers 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.
This wet slab avalanche occurred earlier this season during a similar weather pattern.
Photo: Bridger-Teton Avalanche Center