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RegisterDec 21st, 2019–Dec 22nd, 2019
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Give the snowpack time to gain strength and to adjust to the impressive recent storm totals. Avoid traveling on open slopes greater than 35 degrees where you could start an avalanche. If you are traveling in the Crystal area, be aware very large and destructive avalanches have been observed over the past two days.
The West South zone is demonstrating its diversity as several very different snowpacks and avalanche hazards emerge from this storm cycle. You may experience locally lower avalanche danger in locations that did not receive the impressive water amounts of Paradise and Crystal. In all locations, this was a potent winter storm and current conditions deserve respect. The raging storm and limited visibility hampered observations resulting in a high degree of uncertainty.
Very large avalanches were reported again Saturday from the Crystal Mountain area. These avalanches illustrate the potential for very destructive events failing on layers deep in the snowpack.
A very large (D3) avalanche triggered with explosives on Saturday by Crystal Mountain Ski Patrol. E aspect 6700ft. Photo: Crystal Mountain Ski Patrol
An NWAC Professional Observer traveling in the Paradise area did not observe any recent avalanches.
December 19th, 2019 (The regional synopsis is updated every Thursday @ 6 pm)
Let’s take a moment to recap what happened over the past week:
A potent winter storm arrived on the 12th, adding to the very shallow snowpack throughout the region. Anywhere from 6-36” of snow fell between the 11th and 15th. Places like Mt Baker, Paradise, Mt Hood, and White Pass were the winners regarding snowfall, with quite a bit less for areas further east of the crest like Mission Ridge, Blewett Pass, and Washington Pass.
The most notable avalanche activity occurred in the Mt. Baker backcountry where numerous human triggered storm slab avalanches occurred (with several big enough to injure, bury, or kill a person). The majority of these occurred on upper elevation, north and east facing terrain. Besides the danger posed by the size of the avalanche, many slides quickly revealed rocks and other obstacles barely hidden below the snow surface.
The storm layer took time bond with the underlying snow surface, and we saw the likelihood of triggering slab avalanches slowly decrease over a handful of days. The avalanche danger was at Considerable for many places on Saturday the 14th, then tapered to Moderate on Sunday, and eventually reached Low in many places by Tuesday and Wednesday.
A large, human triggered avalanche on the old snow interface. East aspect of Table Mountain (West-North Zone) at 5,500ft. December 15,2019. Photo by Brooks Broom.
Backcountry travelers have noted generally thin and shallow snowpacks, with a range of structures across the region. Many folks were skeptical of the layering they found. People were able to dig down and observe weak layers in many areas. These were buried in late November and early December. In some places they presented as weak snow over a crust, in others, a layer of feather-like surface hoar. Cold temperatures have likely preserved many of these layers, and will be worth considering as the snow piles up.
Below is a list of commonly visited locations and their snowpack depths in inches (as of December 19th at 4am). Check the weather station hourly data feed and watch as the subtropical javelin of moisture (also known as a strong atmospheric river) changes conditions dramatically over the next few days.
Total Snow Depth in Inches as of December 19th at 04:00 AM.
-Matt Primomo