Storm Slabs
- Alta quota
- Limite del bosco
- Sotto il limite del bosco
- Probabilità
- Likely
- Dimensione
- 1.5–2.5
12-18 inches of snow is forecasted over the next 24 hours along with rising temperatures. Freezing line is expected to reach 2000 feet during the day with moderate to heavy rain possible in low lying areas by this afternoon. Above 2000' heavy snowfall and moderate southeast winds will quickly elevate the avalanche hazard making human triggered avalanches likely 1-3 feet in depth on slopes that are steeper than 30°.
Over the last week we have had several small storms produce a couple of inches at a time building a shallow storm slab atop a very hard and strong bed surface. In some areas a layer of surface hoar was buried in tact on 3/9 that has produced multiple small (D1) skier triggered avalanches over the last few days. Areas where this buried surface hoar (BSH) did not exist good stability has been found as slowly accumulating snowfall has allowed the upper snowpack to accept new snow with minimal stress being applied. With heavy new snowfall arriving we are expecting the 3/9 BSH layer to become more likely to trigger with more dangerous D2 avalanches the result that would be big enough to injure, bury or kill a person. Natural avalanches will become possible today as well. The distribution of this layer is still in question, however it has been identified in multiple locations in our Continental forecast zone on the northerly side of the compass from 3k-6k feet. This layer has not been identified near the Port of Valdez or the top of Thompson Pass. With that said we are not ruling out the possibility of this layer existing in those areas as BSH is notorious for being spotty in its distribution.
Areas where 3/9 BSH does not exist and stability was previously better are expected to become unstable as well due to an overloading of the upper snowpack by heavy snowfall and rising temperatures. The differnce between the 2 snowpacks decribed above is that where BSH is present human triggered avalanches will be more sensitive, deeper and could have long propagations. Where the layer is lacking expect avalanches to involve only the most recent snow and fail in smaller pockets.
Make conservative terrain choices today and use cautious route finding techniques. Areas where wind is redistributing new snow will be more sensitive. Watch for signs of instability such as shooting cracks, collapsing , and recent avalanche activity that would indicate that unstable snow exists where you are travelling.
