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RegisterJan 4th, 2019–Jan 5th, 2019
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At upper elevations, avalanches may be deep and unsurvivable. Dangerous conditions exist after another significant storm has added more snow over a very weak layer. Stay off of, and out from underneath slopes steeper than 30 degrees if you see signs of danger like recent avalanches, and shooting cracks.
When digging around for information today, the most common response was “I thought about going out, but the snow quality seemed low.” We are in the dark regarding what happened during the storm. We do know that we picked up anywhere from 0.3” to 1.2” of water equivalent, with the Salmon la Sac being the winner. Conditions are likely very dangerous in that area, and as one goes up in elevation.
Mission Ridge and Blewett Pass only picked up a few inches of new snow. A freezing rain crust formed up to about 4500ft across the eastern slopes, with a rain crust likely up to at least 6,000ft. Above 6,000ft the new snow is likely sitting on a recent crop of surface hoar and/or facets, which could make for poor bonding and potentially wide avalanches.
Slide on buried surface hoar triggered from a distance on 12/31 above Leavenworth. East at 6,400ft.
The first few days of 2019 were active here in the Northwest. A strong weather system impacted the region bringing warm temperatures, heavy precipitation, and strong winds. This weather system did not impact the forecast areas equally. Even within the same forecast zone we can see wide discrepancies in precipitation numbers. The snowpack you encounter this weekend will be largely dependent on where you go and the elevation at which you travel
Storm Precipitation Totals as of Friday Afternoon
Hurricane Ridge: 2.41”
Mt Baker: 6.52”
Stevens Pass: 2.58”
Snoqualmie Pass: 2.27”
Crystal Mountain: 0.52”
Paradise: 2.23”
White Pass: 0.55”
Washington Pass: 1.05”
Mission Ridge: 0.31”
Mt Hood Meadows: 0.51”
A few big stories stand out in the current snowpack: recent avalanche warnings in the northern zones, persistent slabs in the western areas, and a complex and weak snowpack in the eastern zones.
The northern zone experienced the brunt of this latest weather system. This led to two days of avalanche warnings and at least one large natural avalanche cycle. It's tough to say what the snowpack looks like in areas near and above treeline, but we know those areas received substantial new snow.
Photo: Large natural avalanche at Mt Baker Ski Area during the recent storm. -Mt Baker Ski Patrol
Earlier in the week we began forecasting a new persistent slab in our west-slope zones. A layer of buried surface hoar produced avalanches last Saturday, Sunday, and Monday. How did that layer fair after this recent round of weather? In locations like Mt Baker and Paradise, it was well tested with heavy precipitation. In other locations, less water may not have adequately stressed the weak layer. As visibility improves and more observation come-in the picture may become more clear.
Photo: Large remotely triggered persistent slab avalanche in the Crystal backcountry: Jeremy Allyn
In the eastern zones a complicated and weak snowpack exists. Several persistent weaklayers have plagued these regions most of the winter. Don’t expect this to change anytime soon. Snow profiles and snowpack test can give you a glimpse into the persistent layer. Remember, snow profiles cannot prove the absence of a weak layer or that a layer has “healed.”
Photo: Large remotely triggered slide on buried surface hoar from Christmas above Leavenworth on 12/31: Matt Primomo