Watch for soft slabs where recent snow has been loaded into lee features as the wind picks up Thursday. A big warm up is on its way for Friday.
Recent wind direction has varied from southwest to northwest. Watch for fresh wind slabs forming through the day with forecast winds building to strong.
Wednesday night: Flurries bringing 5-10 cm new snow. Moderate northwest winds. Alpine low -10 C. Freezing level 1200 m dropping to valley bottom.
Thursday: Mix of sun and cloud. Light southwest winds building to strong. Alpine high -4 C. Freezing level rising to 1000 m.
Friday: Broken cloud with flurries bringing 10-20 cm new snow turning to rain. Moderate southwest winds. Alpine high +2 C. Freezing level rising to 2200 m.
Saturday: 10-20 mm rain to 2000 m. Strong southwest winds, extreme at ridgetop. Alpine high +4 C. Freezing level 2000 m dropping to valley bottom by Sunday morning.
On Sunday through Tuesday, storm slabs were reactive to skier traffic, producing avalanches up to size 1.5 on north to east aspects in the alpine. Natural storm slab activity has tapered since the weekend but a few have been observed up to size 2 out of steep, unsupported headwalls as recently as Monday.
On Tuesday, explosive work released a cornice which triggered a deep persistent slab over 2 m deep in a chute below. On Monday, two deep persistent slab avalanches were reported in shallow snowpack areas on southwest aspects around 2000 m, with crown depths of 1 m or greater. A size 1.5 was vehicle triggered above a cut bank. A size 2.5 was remotely triggered by a skier in a thin to thick snowpack area.
Recent snow and wind have formed soft slabs in terrain features lee to northwest through southwest winds. Around treeline, the upper snowpack contains several crusts from recent warm temperatures and rain events, some observed as high as 2100 m.
A layer of surface hoar is buried 80-120 cm below the surface in sheltered areas around treeline. It has not seen any 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.
