Avalanche Forecast

A frontal system on Thursday should produce light snowfall in the northeast Cascades and light to moderate snowfall in the south and central east Cascades during the daylight hours. 

New and recent snow will be deposited on lee NW through E aspects, although initially be wary of lingering wind slab on S-SE slopes from transport earlier in the week. Most avalanches should stay within the new storm snow, but a few may step down to older storm layers or crusts in isolated locations.     

If snowfall and winds increase faster than expected watch for increasingly sensitive storm layers. Generally avoid wind loaded terrain in the near and above treeline zone with new and recent snowfall being transported to a variety of aspects.

The storm related avalanche danger will increase further Thursday night into Friday morning.  

Continue to watch for signs of the PWL mainly in the central east zone. Snowpack tests may be helpful for identifying PWLs as well observing whumping and shooting cracks.You don't want to take big chance when this type of layer may be present, especially during new loading.

An atmospheric river around Dec 9th produced steady snowfall in the northeast zone, rain in the southeast zone, with a transition in between in the central east zone. Over the last week, about 1/2 - 2 feet of snow fell along the east slopes.

In the central east zone we are still concerned about the sensitivity of a PWL formed during cold weather at the end of November. On Wed 12/9, NWAC pro observer Tom Curtis was at Blewett Pass and found sudden collapse test results in faceted snow 15 cm from the ground. On Thu 12/10, Tom found similar sudden collapse results due to buried surface hoar at about 50 cm down at 5100 feet on the north side of Mt Cashmere while experiencing whumpfing and hearing a natural avalanche. Further east in the central east zone, the Mission Ridge pro patrol did not find evidence of a lingering PWL last Friday. Closer to the Cascade crest in the central east zone, recent NWAC observations suggest that the PWL was destroyed or subdued by the rain event. With heavy loading and few signs of instability at Washington Pass, persistent slab was removed as a problem in the northeast zone, but it will be retained in the central east zone until more observations are received. 

Recent guide reports from the Washington Pass zone indicate strong northerly winds redistributing recent snow on lee southerly aspects above treeline. The most recent storm snow was reported to be well bonded to the underlying crust, with good ski conditions found in non-wind affected terrain.  

The southeast zone should have a much shallower snowpack more affected by recent rain and warm temperatures. However we have no recent observations from the southeast zone.