It looks like one more dry day before the next round of warm storms hit the Coast this week.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Monday: Cloudy with flurries. The freezing level rises to 1200-1400 m and winds are light or moderate from the S-SW. Tuesday: Periods of snow – 15-25 cm. The freezing level is around 1400-1600 m. Winds increase to moderate or strong from the SW. Wednesday: Moderate to heavy snow or rain. The freezing level spikes to around 2000 m and winds remain strong from the S-SW.
Avalanche Summary
No new natural avalanche activity was observed on Saturday. Explosives control produced mostly small (size 1) storm slabs with a couple deeper size 2 slabs from steep rocky slopes. Clear weather gave a better picture of the widespread natural cycle on Thursday and Friday. Most observers reported numerous size 2-3 slabs from all aspects and elevations. Many of these slabs released on the mid-January surface hoar, released on relatively low angle slopes, and showed very wide propagation.
Snowpack Summary
The "Pineapple Express Light" dumped 80-160 mm of precipitation on the South Coast this week. Most of this fell as snow above 1800-2000 m (over 1 m) with mixed rain and snow or just heavy rain below 1800 m. Heavy snow and strong winds have formed deep and dense wind slabs in exposed lee terrain and caused substantial cornice growth. Expect to find a rain crust at or near the surface (below 10-20 cm of fresh snow) at lower elevations. The early and mid-January surface hoar layers may have been wiped out by the storm and subsequent avalanche cycle. These layers would be down between 100 and 150 cm deep now. Tread cautiously until we know more about the state of these persistent weaknesses. The mid and lower snowpack is generally strong, with the exception of shallower snowpack areas that may be more faceted.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
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.