Another storm event is on its way for the weekend. While this one is expected to be cooler than Wednesday's deluge, snowfall amounts are uncertain. Heavy snow, wind and rain will increase hazard.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
Friday will see a continuation of Thursday's drying and cooling trend before the next wave of warm and wet precipitation returns on Saturday.FRIDAY: Flurries, accumulation 10-20 cm. Strong southwest wind. Alpine temperature -1. Freezing level 1200 m.SATURDAY: Snow, accumulation 20-30 cm. Moderate to Strong south wind. Alpine temperature 1. Freezing level 2000 m.SUNDAY: Wet snow or rain, accumulation 20-30 mm. Strong south wind. Alpine temperature 2. Freezing level 2200 m.
Avalanche Summary
Following the November 17-19 storm, a natural avalanche cycle produced storm slabs to size 3 on predominantly northerly aspects in the alpine and at treeline. Cornices were also touchy and large for this time of year and producing large avalanches after releasing onto slopes below. Subsequent warm weather and rain to mountain tops produced numerous loose, wet avalanches as rain drenched all elevations. Expect this activity to subside during the cooler drying trend on Friday but then increase again during the next storm event on the weekend.
Snowpack Summary
Cooler temperatures and lowering freezing levels have formed a 2 cm thick crust at 1800 m and above. Below this crust the upper snowpack is saturated down 30 cm to the November 21st crust at alpine elevations while at treeline and below the entire snowpack as been soaked through to ground. The November 9th crust/persistent weak layer combo near the bottom of the snowpack is now down 150 - 240 cm in alpine and glaciated terrain.
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.
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.