Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
The first frontal system will cross the south coast Thursday night and Friday morning. There is some uncertainty regarding the timing but the second system is expected on Saturday and should persist through Sunday.Thurs. Night/Friday: Snow 15-20cm, freezing level am: 1000m pm: 1500m, ridgetop wind light SW-WSaturday: Moderate-heavy snowfall, freezing level am: 800m pm: 1200-1500m, ridgetop wind 20-40 km/h S-SWSunday: Light-moderate snowfall, freezing level am: 1200-1500m pm: 1000m, ridgetop wind 30-50 km/h SW
Avalanche Summary
No new avalanches have been reported. Loose wet sluffing has been reported form steep solar aspects during the heat of the day.
Snowpack Summary
The storm snow from last weekend has settled rapidly and is bonding well with the snow below. There are two persistent weak layers which remain a concern but the problem is becoming isolated. The early-March crust/facet layer is down roughly 1m and the early-Feb layer is down 1.5m or more. These layers are typically deep enough that human-triggering is unlikely but smaller avalanches or cornices have the potential to step down to these layers. Strong SW winds during the storm created widespread wind slabs on lee features in the alpine. These are breaking down and getting harder to trigger but may still pose a threat in some areas.Freezing levels have been cycling between valley bottom and 1500-2000m, and low elevation terrain saw significant rain last weekend. The snowpack at lower elevations is generally stable but it may be possible to trigger loose wet activity from steep terrain during the heat of the day. On the surface, a well developed sun crust has formed on solar aspects. Surface hoar has formed and is most prominent in sheltered areas and on north aspects. At lower elevations, a crust can be expected in most areas.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.