Warming temperatures may increase the reactivity of recently formed wind slabs. Use extra caution around steep south facing slopes in the afternoon if the sun is shining brightly.
Recently formed wind slabs are expected to remain reactive to human triggering in exposed terrain. These slabs may overlie a weak faceted surface from the extended cold period and could remain reactive to human triggering for longer than normal.
Wet loose avalanches are possible on steep low elevation slopes if the temperature is above freezing. Loose avalanches are also possible on steep south facing slopes if the sun is shining brightly.
A ridge of high pressure brings dry and sunny conditions for Thursday before the next storm system reaches the coast Thursday night.
Wednesday Overnight: Mainly cloudy, light variable wind, freezing level as high as 800 m.
Thursday: A mix of sun and cloud, light variable wind, freezing level as high as 900 m.
Friday: Snowfall 4-8 cm, strong SW wind, freezing level as high as 1400 m.
Friday overnight and Saturday: Snowfall 5-10 cm, strong SW wind, freezing level climbing as high as 1200 m.
On Tuesday, a natural icefall triggered size 2.5 wind slab was reported on a NE aspect. At lower elevations closer to the coast where it was warmer, loose wet avalanches were observed. This MIN report and this one describe some recent wind slab activity.
On Monday, loose dry avalanches up to size 2.5 were reported in the northwest of the region where upwards of 50 cm of recent storm snow had accumulated. No new avalanches were reported in the south of the region where substantially less storm snow had accumulated. On Sunday, a natural wind driven avalanche cycle was reported through many parts of the region.
15-30 cm of recent storm snow has been redistributed by periodic moderate to strong SW winds which has formed reactive wind slabs and created a heavily wind affected snow surface in the alpine. The recent storm snow overlies a previously wind-affected surface comprised of old hard wind slabs, sastrugi, and areas scoured to the ground or old crusts. Faceting above the old surface from the prolonged cold temperatures may increase the reactivity of the recently formed wind slabs which could end up persisting for longer than normal. With the mild temperatures and ongoing wind, cornices are reported to be growing larger.
The base of the snowpack is composed of crusts and weak faceted grains, particularly in thin snowpack areas. While these layers have generally gone dormant in the region, they still have the possibility of waking up with new snow load or warming, and wind slab avalanches may still have the potential to step down to these deeper layers in isolated areas.
