Avalanche Forecast

Moderate - Uncertainty is due to difficult to forecast freezing levels.

Friday night: 5-15 cm new snow with to rain below 1500 m. Strong southwest winds. Freezing level dropping to 1600 m.

Saturday: 10-15 cm new snow in most areas with localized hot spots receiving up to 25 cm. Rain below 1400 m turning to snow as freezing levels drop after noon. Strong southwest winds, extreme at ridgetop. Freezing level hovering around 1500 m during the day, dropping overnight.

Sunday: Sunny. Wind easing to light northwest. Alpine high -4 C. Freezing level valley bottom.

Monday: Sunny. Light northwest wind. Alpine high -5 C. Freezing level valley bottom.

A widespread storm slab avalanche cycle up to size 2 was observed Friday. Reports on Thursday were of a natural wind slab avalanche cycle, mostly size 2 at alpine and treeline elevations. The cycle was likely induced by a change in wind direction from southwest to northwest redistributing previously wind loaded snow. 

Reports of deep persistent avalanches have been periodically coming in from the western boundary area over the past few weeks and most recently on Friday in the southwest Valhallas. They are generally triggered by very large loads (cornice falls or vehicles) or from shallow, rocky snowpack areas. Loading from new snow and rain will further stress these buried weak layers where they exist.

10-25 cm of new snow is falling on a crust suspected to exist below 1800 m (where it rained Friday). In the alpine, storm totals of 30-50 cm are being ravaged by strong to extreme winds. Below 1400 m, the snowpack continues to soak up rain.

A layer of surface hoar is buried 100-150 cm below the surface in sheltered areas around treeline but has not been associated with avalanche activity recently. Weak basal facet/crust layers are particularly noteworthy in the western Boundary area. The few recent avalanches associated with this problem have been triggered either by very large loads or from shallow, rocky snowpack areas.

• Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
• Minimize exposure during periods of heavy loading from new snow, wind or rain.
• Be aware that wet activity at low elevations is a classic situation for step-down failures in deeply buried persistent weak layers.