Avalanche Forecast

The strong warm front that has caused heavy rain most of Tuesday is expected to pass by early Wednesday with cooling and a period of light to moderate precipitation along with continued strong winds.

Further cooling and lighter showers are expected later Wednesday with strong southwest winds shifting to strong westerly winds.

Update Wednesday morning: In most of the Cascades this weather will cause a transition in the snowpack from wet and saturated surface layers to a draining and gradually refreezing upper snowpack.

But cooler conditions in the central east zone and especially the northeast zone are likely to maintain previous layers and persistent weak layers in the snowpack!

Do not assume that these layers have stabilized in the central east and northeast zones!

The total snow gage at Washington Pass shows an additional 14 inches of snow in the past 24 hours ending Wednesday morning. This snow will be loading previous layers and persistent weak layers in the snowpack. This is still a potentially very dangerous snowpack in the central east zone and the northeast zone. Back country travel is still not recommended in the northeast zone on Wednesday. Conditions are also still very uncertain in the central east zone on Wednesday.

Weather and Snowpack:The northeast and north central Cascade zones have the deepest snowdepths found throughout the Cascades this season thanks to cold air pooling on the east side in otherwise warm storms for the west. 

Snowdepths along the east slopes are generally in the 1-5 foot range with the greatest snowdepths in the northeast zone and the shallowest near Blewett Pass and in the southeast zone. However, strong storms Sunday and Monday were heaviest along the south, so snowdepths are beginning to even out from north-south.

We had a wet and wild November and this formed a strong crust by mid November in all areas.

A long stretch of cold weather led to widespread near surface faceting and surface hoar formation along the east slopes in late November.

The weather so far in December has become very active with periods of heavy snowfall over the past week with an overall warming trend Monday, culminating in a downpour of rain all day Tuesday at high freezing levels.

This weather and snowpack scenario caused ripe avalanches conditions, though few reports have been received as it hasn't been the most pleasant of conditions over the past few days.

Reports:

The most important report for along the east slopes comes from Mission Ridge Ski Area on Sunday where the pro patrol reported numerous and often sympathetic easily triggered slab avalanches of about 8-16 inches releasing on a rain crust from early December. One very large explosively triggered slab avalanche on the northeast slope of Windy Ridge was 5 feet deep and propagated several hundred feet which released on the mid November crust.

Increasingly large persistent and storm slab conditions were found in the Smith-Brook area. just east of Stevens Pass Sunday by NWAC's Dallas Glass. These conditions may be susceptible to natural avalanches with additional loading or a change to rain, possibly before the next storm arrives Tuesday!

NWAC observer Jeff Ward was at Washington Pass on Friday and was surprised by the lack of activity on the potential PWL and considered the conditions uncertain.

With varying amounts of rain received along the east slopes Tuesday, it is still too early to tell the current state of that persistent slab problem and how it has or has not changed. This layer may still be reactive, though likely less so now following the rain event. Still best to proceed with caution until more definitive observations come in.