Avalanche Forecast

Moderate - Due to the number of field observations

WEDNESDAY: Mostly sunny, moderate westerly winds, alpine temperature near -13 C, freezing level below valley bottom.THURSDAY: Partly cloudy, light easterly winds, alpine temperature near -12 C, freezing level below valley bottom.FRIDAY: Mostly sunny with increasing cloudiness, light to moderate southwesterly winds, alpine temperature near -11 C, freezing level below valley bottom.

On Monday, a few small slab avalanches (size 1 to 1.5) were reported on northerly to westerly aspects, triggered by small cornice chunks and skiers.  They were 10 to 30 cm deep and in treeline and alpine terrain.Avalanche activity may slow down with a period of cold, clear weather that is expected to persist this week.  However, the sun is packing more of a punch as the days get longer and it will warm the snow surface on solar aspects if clear skies prevail. Watch for steep sunny slopes due to the sun’s influence, lee features for reactive wind slabs, and be extra cautious near thin spots and shallow snow pack areas where triggering a deeper weak layer is more likely.  There is a lower probability of triggering a deeper layer than in previous weeks, but the consequence would be very high if one was triggered.

Around 50-80 cm of recent snow with strong winds have created wind slabs in direct lee features. On steep solar aspects, a thin sun crust exists.  These overly a layer of surface hoar, graupel, and a melt-freeze crust buried mid-February.  The melt-freeze crust exists up to 1700 m in elevation.Deeper in the snowpack, a widespread weak layer from mid-December composed of facets, crusts, and surface hoar is 120-160 cm deep. Also, a rain crust with sugary facets buried in late November is near the base of the snowpack. If triggered, these weak layers could produce large, destructive avalanches with high consequences.