Persistent warm temperatures are penetrating and destabilizing the upper snowpack. Natural avalanche activity is possible especially on sun exposed slopes. Avoid travel under avalanche paths especially with looming cornices overhead.
Weather Forecast
Warm temperatures persist through the forecast period. WEDNESDAY: Sunny with cloudy periods and treeline temperatures near +16 degrees. Ridgetop winds moderate from the southast and freezing levels above 3000 m. THURSDAY: Mix of sun and cloud. Treeline temperatures +10 degrees with freezing levels 2300 m. Ridgetop winds light from the southwest. FRIDAY: Cloudy with isolated rain showers and some flurries at higher alpine elevations. Treeline temperatures near +4 degrees and freezing levels dropping to 2000 m. Ridgetop winds moderate from the South.
Avalanche Summary
On Monday, a widespread natural wet loose avalanche cycle occurred and was reported up to size 1.0. As the heat continues to penetrate the snowpack we suspect natural wet avalanches will continue through the forecast period.
Snowpack Summary
Snow surfaces are variable and the heat has likely eliminated any trace of cold snow except on high elevation north features. Melt-freeze conditions (more melt then freeze at lower elevations) exist on all other aspects and elevations and signs of snowballing, surface sluffing and loose wet avalanches are current.Deeper in the snowpack a layer of weak and sugary faceted grains sits on a melt-freeze crust about 50 to 120 cm deep. This layer is most prominent in the North Shore Mountains on north aspects. With little overnight re-freeze the warm temperatures will penetrate deeper and continue to destabilize the snowpack and possible imitating larger persistent slab avalanches. It’s hard to say how many hot days and warm nights it will it take to wake up the more deeply buried weak layers that we haven't thought about in a long time.
Problems
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.
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.