Monday is the last day of the 2012/13 forecast season. As of Tuesday, general spring messaging will be found under the "Forecast Details" tab.
Confidence
Fair - Due to variable snowpack conditions
Weather Forecast
Saturday night - Sunday: Light to moderate snowfall in the south of the region (Coquihalla/ Allison Pass) on Saturday night. By morning skies are expected to be overcast with clearing in the afternoon / Light and variable winds / Freezing level at about 1500mMonday: Generally clear skies / Light north winds / Freezing level at about 1800m
Avalanche Summary
Throughout the past week, numerous rider triggered and isolated remote/sympathetic events have been reported in high (2300-2700m) north and northeast facing slopes up to size 2.5, all associated with preserved surface hoar. The aseems to be occurring in the north of the region in the Duffey Lake/ Birkenhead areas, through the Hurley and up towards Bralorne/Goldbridge.
Snowpack Summary
Generally light daily snow accumulations have been observed over the last week, with higher accumulations in the Coquihalla/Allison pass areas. Soft wind slabs likely exist on lee terrain. At lower elevations, spring temperatures have created isothermal snowpack conditions.About 30-60 cm below the surface lies the April 5th interface. On solar aspects, the layer is a strong melt-freeze crust, with some faceting observed above and below. On Northwest to Northeast aspects above about 2300m, this interface may be preserved surface hoar (up to 15mm). Where the surface hoar is present we have reports of sudden results in stability tests and have seen rider triggered, sympathetic and remote events up to size 2.5. Although this interface may be gaining some strength, continued reactivity is expected with the potential for large avalanches.Cornices are huge and will continue to grow with the forecasted precipitation.
Problems
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
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.