Storm Slabs
- Alta quota
- Limite del bosco
- Sotto il limite del bosco
- Probabilità
- Possible
- Dimensione
- 1–2
Shallow storm slabs will continue to form today with 4-8" of snowfall expected above 1000' in the next 24 hours, the majority falling tonight. The higher amounts of this range are expected to occur in the higher terrain of the Maritime zone and near Thompson Pass. This snowfall will be accompanied by light - moderate E-SE wind. Yesterdays weather brought a trace of snowfall for most areas with Valdez once again having temperatures rise above the freezing mark. A slow and steady build up of storm slabs will continue the Moderate avalanche hazard where human triggered avalanches are possible in specific spots 6-18 inches in depth. The most likely areas to encounter instability will be places where new snow is being redistributed into deeper pockets. This could exist near high elevation ridgelines, the lee side of terrain features and cross loaded terrain. Areas in close proximity to the Thompson Pass gap will have a higher concentration of these wind loaded slopes. Whereas moving north or south from this wind funnel will lower the concentration. Continous cloudy weather and snowfall has prevented travel above 4000' for the last 4 days creating uncertainty in the forecast.
Other areas that would be a concern would be mid and low elevations where this new snow has accumulated on top of surface hoar. Surface hoar is a notoriously weak layer because it is strong in compression and weak in shear. There are a couple of reasons why this weak layer is expected to be limited in its effect in our sitiuation. The first is that formation of this layer was only observed at and below brushline. Secondly, most areas below brushline are still very thick with exposed alders, which will prevent continous slabs from building. Areas at mid and low elevations on Thompson Pass could be a concern where steep open slopes exist. Steep slopes just above brushline could be a concern as well. Rain at low elevations of the Maritime zone have destroyed this layer.
This layer was identified in the Cracked Ice zone but was absent near Thompson Pass on Little Oddessey and Loveland Basin where wind prior to the recent snowfall would have knocked it over before being buried.
Pay attention to new snow depth and wind redistribution patterns. Watch for signs of instability such as shooting cracks, collapsing and recent avalanche activity. Hasty hand shear pits and small test slopes are a great way to quickly gather information about the stability of the upper snowpack in the area you choose to travel.
Photo: NWS