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RegisterApr 8th, 2018–Apr 9th, 2018
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The avalanche danger will rise Monday as sunshine and warm temperatures quickly make recent snow unstable. You can encounter a variety of avalanche dangers, including Wind Slabs, Loose Wet avalanches, Cornices and Glide avalanches. Use visual clues such as fresh cornices, wind drifted pillows and cracks in the snow all indicating that you could trigger a Wind Slab avalanche. Give fresh Cornices a wide margin of safety and limit exposure on steep sun exposed slopes or where the surface snow is becoming wet.
Rapid clearing, sunshine and warming is expected Monday. This should cause an increase in the avalanche danger Monday, following the weekend's strong winter-like storm cycle.
Fresh wind slabs will be easy to trigger on steep lee slopes below ridges at higher elevations and features where wind drifted snow exists.
Recent storm snow and old snow will become wet, making Loose Wet avalanches possible, especially on steep sun exposed slopes during the late morning and afternoon. Watch for signs of wet snow conditions such as sluffing, roller-balling and any natural Loose Wet avalanches.
Cornices have grown large in many areas and will become fragile with the sun and warming. Give cornices a large margin of safety and avoid travel on slopes below, as cornice failures may trigger large avalanches on slopes below.
A strong storm over the weekend caused rain Saturday to high elevations followed by cooling and new storm snow by Sunday afternoon. A wide range of new snow amounts will exist along the east slopes of the WA Cascades with the greatest amounts nearer the crest and at higher elevations. The new snow was transported by periods strong winds that built fresh Wind Slabs on a variety of aspects, especially below ridges.
The recent storm built fresh cornices along exposed ridges.
Up to 6 inches of snow was received last week. Strong W-NW winds redistributed recent snow onto lee slopes above treeline forming shallow wind slabs.
Older layers of weak snow can be found in the snowpack. We have limited information about the distribution and reactivity of these layers leading to a higher level of uncertainty. If you have any information or observations on layers within the snowpack please consider submitting them to NWAC via our public observations page. The exact weak layer and depth depends on your location. Common weak layers are:
Rainfall and continued above freezing temperatures Friday night and Saturday morning may allow Wet Slabs to fail at these interfaces. Peristent Slabs may be reintroduced when we receive more snowpack information following this storm cycle.
Observations
North
On 3/23, professionals near Washington Pass reported the 3/8 buried surface hoar was reported as 1.5 feet (45cm) below the snow surface.
Central
On Friday 4/6, professional observer Matt Primomo traveled up the Icicle to above Colchuck Lake. Matt found a moist and well settled snowpack below 5800' with no persistent weak layers. The 2/8 crust was 1 m down. At 6700' on a NNE aspect, Matt found preserved stellars 14 in (35 cm) down and showing a likelihood to propagate in snowpack tests. Dry snow was found at this elevation below the top 8 " (20 cm). Higher in the terrain, recent wind slab avalanches likely released on this layer. Matt also observed natural loose wet avalanches and one wet slab avalanche above treeline on a SE aspect.
On Saturday 3/31, an observer reported a large slab avalanche that likely failed on a persistent weak layer 4-5 feet below the surface in the Enchantment Mountians
On Friday 3/30, Matt Primomo was on Dirtyface Mountain where he found two buried surface hoar layers (3/22) on shaded aspects at variable depths within the two feet of the snowpack. Test results indicated the potential for propagation on both weak layers. Snow pits indicate a weakening 2/8 crust.