Check out the latest post on the Forecaster's Blog for advice on how to stay safe in the backcountry over the holidays.
Confidence
Poor - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
A series of frontal systems will affect the region over the next several days bringing periods of moderate to heavy precipitation followed by brief dry spells. Monday: 20-35cm of snow. Moderate to strong S-SW winds. Freezing level (FL) around 800m. Tuesday: 10-15cm. Moderate W-SW winds. FL 1000m rising to 1800m in the evening. Wednesday: 20-30cm. Moderate W-SW winds. FL around 1800m.
Avalanche Summary
Numerous Size 1-2 slab avalanches have been reported in the past 48 hours, primarily in wind affected terrain near ridge crests. Expect the size and likelihood of avalanches to increase through the forecast period.
Snowpack Summary
The region received 20cm of new snow on Friday night and throughout Saturday. Touchy windslabs up to 50cm deep have formed on north through east aspects in response to strong SW winds. A weak rain crust is found below the new snow up to treeline elevations. This crust may sit on top of buried surface hoar and/or facets may persist 10-20cm below. Watch this layer as it gets more load and a thick cohesive slab develops, particularly below treeline where the buried surface hoar would be especially large. A strong mid pack overlies basal facets that have also gained considerable strength. Snow depths are at approximately 140cm at treeline in the Spearhead area and 180cm at treeline in the Brandywine area.
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.
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.