Northwest Avalanche Center

Observation: Public

All Observations

Observation Details

Name:
Matthew Crisler
Observation Date:
December 19, 2020
Submitted:
December 19, 2020
Zone or Region:
West South
Activity:
Skiing/Snowboarding
Location:
Mount Rainier - Tatoosh

Observed Avalanches

Did you observe any avalanches? 
Yes
Avalanche Type:
Hard Slab
Size:
Size 1: Relatively harmless to people
Elevation:
5500
Aspect:
NE
Comments:
Crown a few centimeters deep naturally triggered apparently by some falling snow from a tree onto a steep NE aspect that was actively loading. Very shallow, but propagated across a large portion of the slope. Located in the steep slopes just separated from the skin track below Pinnacle Peak.

Also noticed a few other small pockets of wind slab in abnormal locations with similar triggers from falling snow.
Photo:

Signs of Unstable Snow

None reported

Observations

With the obvious potential for Wind slab, we steered well clear of steeper loaded slopes. In doing so, we did not observe shooting cracks or other signs of unstable wind slabs. Near and below treeline winds were calm across both N and S aspects with pretty heavy and moist snow from the transition into treed terrain. Lower down (though still >5000 feet) and unpredictably dispersed there was an apparent zipper rain crust underneath 2-3 cm of snow making for some challenging travel conditions.

Media

What looks like the remnants of a small wind slab pocket at ~5800' near the trees to the left of the skin track up the slope below The Castle.
Some roller balls from snow dropping from trees along Stevens Canyon Rd. Not sure if this is just wet snow on the ground or the impact of the brief sunshine early this morning.

Advanced Observations

Observed Avalanche Problem #1: 
Wind Slab
Comments: 
In the open alpine regions, wind was swirling and unpredictable. It was a bit challenging to tell what was stripped and what was loaded other than everything out in the open being pretty stripped. Slightly down from the ridge at the castle it appeared to be blowing downslope (S), but nearer the ridge it was more up and slightly across the slope (NW). Winds were mostly calm at and below treeline.
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