Latest NWAC report -- areas of special note
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Snowpack Analysis:
Heads up folks because the avalanche picture has greatly changed in the Washington Cascades from the past couple weeks.
Dangerous persistent large hoar frost that formed during the latter part of the recent 2 week fair weather period has been buried in the Washington Cascades mainly at Stevens and Snoqualmie and east of the crest. By the end of Thursday this persistent layer will be found in these areas under anywhere from a couple inches to a couple feet of the recent storm snow.
Surface hoar layer with thin rimed crust before it was buried near Rainy Pass, about 4600 feet, 28 January, Photo by NWAC Observers Jeff Ward and Dallas Glass.
NWAC observers at Stevens and Snoqualmie today report snowpack whoomping, easy sudden collapse pit tests and Extended Column tests indicating propagation due to the persistent buried hoar frost layer including on your favorite go to slopes for such conditions - open low angle slopes below treeline. Here is a link to a video made today near Stevens Pass of tests of the buried surface hoar layer.
However a buried hoar frost layer is considered unlikely in the Olympics, west of the crest and on the volcanoes due to rain in those areas at the start of the recent storm. But it will be listed in these areas as an unlikely concern until there is confirmation one way or the other.
The recent storm is also expected to have built new wind slab on lee slopes above tree line. NWAC observers today also report new temporary storm slab on sheltered slopes near and below tree line in the Stevens and Snoqualmie areas. These should be the most important concerns in the Olympics, west of the crest and on the volcanoes.
At least the mid and lower snowpack consists mainly of crusts and melt form crystal layers. The low snow amounts on many south slopes and at low elevations and ample terrain and vegetation anchors are limiting the avalanche danger in those areas.
Detailed Forecast for Friday:
Light snow showers should end Friday morning. Partial clearing should be seen Friday afternoon and night with continued cool temperatures.
There should be little change in snow conditions on Friday.
The top concern at Stevens and Snoqualmie and east of the crest will remain the persistent buried hoar frost slab layer. This layer will be found anywhere from a couple inches to a couple feet under the recent storm snow. Shooting cracks and whoomping are the strongest red flag observations for this persistent layer. Remember that this is also expected on small open slopes below treeline in the Stevens and Snoqualmie areas and east of the crest.
New wind slab is likely to remain on lee slopes above tree line on Friday. Watch for signs of wind transported snow above treeline. Temporary storm slab may survive on Friday on sheltered slopes near and below tree line on Friday. These are the more likely concerns in the Olympics, west of the crest and on the volcanoes.
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