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RegisterFeb 9th, 2017–Feb 10th, 2017
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The forecast for the west slopes of the Cascades has been adjusted to an extreme avalanche danger for Thursday. This means that large to very large loose wet or wet slab avalanches should be expected along the Cascade west slopes especially in areas that are receiving heavy rain such as Paradise, Crystal and Mt Baker. These are dangerous conditions and all avalanche terrain should be avoided in this area.
A strong wet warm front will lift north over the Olympics and Cascades on Wednesday night to Thursday morning. Plan on rapid warming Wednesday night and heavy rain or snow with higher snow levels through Thursday morning. This should cause an avalanche cycle in the Olympics and Cascades which should test the snowpack.
Update: Snow and now heavy or very heavy rain has fallen since last night at Paradise, Crystal and Mt Baker. Water equivalents for these sites for the past 24 hours is in the 3-4 inch range with more expected until the front crosses the area. The forecast for the west slopes of the Cascades has been adjusted to an extreme avalanche danger for Thursday.
This means that large to very large loose wet or wet slab avalanches should be expected along the Cascade west slopes especially in areas that are receiving heavy rain such as Paradise, Crystal and Mt Baker. Small avalanches may step to deeper layers during the cycle.
These are dangerous conditions and all avalanche terrain should be avoided in this area.
The cold front should cross the Cascades Thursday midday. This should cause a change to showers and lowering snow levels. The avalanche danger should begin to decrease following the cold front Thursday afternoon.
Weather and Snowpack
A strong storm cycle was seen Friday through Monday with about 3-5 feet of snow recorded along the Cascade west slopes.
A slow warming trend affected all areas Saturday 2/4 with rain reaching 4000-4500 feet in the south Cascades. Cool easterly flow kept temperatures locally cool at Pass level at Stevens and Snoqualmie Pass through the day Saturday, with a warm-up Saturday midday following a switch to westerly flow. This created a weak crust layer that has now been found both at Stevens and Snoqualmie down about 3 feet.
A nice day was seen Tuesday with light wind and sun or filtered sun and high clouds allowed for snowpack settlement and stabilization of the deep recent storm snow. Most NWAC snowdepth gages settled about 6 inches or more during the day Tuesday.
Increasing winds, snowfall and warming were generally seen on Wednesday as the next storm approached.
Recent Observations
North
On Tuesday, the Mt Baker pro-patrol reported ski triggered soft slab avalanches of 8-10 inches on average, though they were not propagating widely as the older deep storm snow was showing signs of settlement and stabilization. There was evidence of a widespread natural cycle, likely Monday night on Table Mountain, with many crowns estimated in the 2-4 foot range.
NWAC pro-observer Lee Lazzara was in the Glacier Creek area Tuesday, reporting numerous natural and ski triggered storm snow soft slabs, on average 40 cm (16") on steep test slopes on both southerly and northerly facing slopes. Another ski triggered slide was evident from a nearby party that may have been a bit deeper, about 2 feet.
Central
Reports from both Snoqualmie and Stevens passes Tuesday indicated continued storm snow settlement and stabilization, in the near and below treeline terrain. The thin melt freeze crust formed midday Saturday, 2/4 produced positive snowpit results but no avalanches were produced. The storm snow is gaining strength, showing increasing resistance with depth and providing some excellent conditions.
NWAC pro-observer Jeremy Allyn was in the Henry Creek drainage below Jim Hill on Wednesday and reported that wind transport was underway due to the incoming storm. Quick tests of the near surface snow did not show significant results and ECT and PST tests on the 2/4 interface at 75 cm down did not indicate propagation.
NWAC pro-observers Jeff Ward at Skyline at Stevens and Ian Nicholson near Alpental on Wednesday did find significant signs of instability.
Reports via the NWAC Observations page for Mt Snoqualmie for Tuesday and Wednesday indicate several recent D1-2 slab avalanches on steep terrain features.
South
NWAC pro-observer Dallas Glass was in the Crystal backcountry in Bullion Basin Sunday and found a reactive storm layer 35-40 cm down in snowpit tests on all aspects below and near treeline. Shallower storm slabs could be triggered on test slopes. Storm snow from this cycle had settled to about 60-65 cm. No natural avalanches were observed and recent wind transport was localized to near the ridgeline.