Confidence
Fair - Freezing levels are uncertain
Weather Forecast
Synopsis: The first in a series of frontal systems will reach the South Coast on Thursday afternoon spreading moderate to heavy precipitation through Saturday morning. Thursday: Increasing cloud with precipitation developing in the afternoon. 5-15 mm expected overnight. The freezing level is around 2000 m. Winds increase to moderate of strong from the southwest. Friday: Moderate to heavy precipitation – 15-20 mm. The freezing level drops to around 1600 m and winds are moderate to strong from the southwest. Saturday: Precipitation should ease off during the day and the freezing level continues to gradually drop.
Avalanche Summary
There were no new reports of avalanches on Tuesday. Recent avalanche activity included reports of loose wet sluffs up to size 2 on solar aspects and isolated cornice failures.
Snowpack Summary
Recent warm temperatures have created melt freeze conditions on all aspects below 2000m and to mountaintop on south facing terrain. Isothermal conditions as deep as 100cm have been reported on South aspects at lower elevations. On high north-facing slopes surfaces are well settled and surface hoar development continues in some areas. Cornices are huge and potentially weak. A layer of surface hoar (buried on March 11; now down about 60 cm) is still being observed in some locations. Triggering this layer has become unlikely, and would most likely require a large trigger or from a thin snowpack zone. Mid and lower snowpack layers are well bonded.
Problems
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.