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 5-15cm, freezing level am: 1000m pm: 1500m, ridgetop wind 15-30 km/h SW-WSaturday: Moderate-heavy snowfall, freezing level am: 800m pm: 1400-1800m, ridgetop wind 20-40 km/h S-SWSunday: Light-moderate snowfall, freezing level am: 1400-1800m pm: 1000m, ridgetop wind 40-60 km/h SW
Avalanche Summary
Reports of natural avalanche activity up to size 2 on Wednesday from warming and solar radiation.
Snowpack Summary
The warm weather has resulted in good settlement of the snowpack and most of the layers are well bonded. There are still two weak layers that remain a concern but the problem is becoming isolated. However, the weight of the new storm snow may reactive these layers. The early March layer is down 60-100cm and the early Feb layer is down roughly 1.5m. It seems like these persistent weak layers are more of a concern in the northern parts of the region but may still pose a threat in the Coq and south. In the southern part of the region, widespread moist snow surfaces were reported to mountain top. Dry snow is still expected on northern aspects at treeline and above in the north of the region. A crust can be expected on most slopes and surface hoar has formed on sheltered slopes. In the north of the region, old wind slabs may still be a concern on N through E aspects from the last storm.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.