Avalanche Forecast
Regions: Olympics.
Wet snow avalanches and cornice failures will be the primary concerns Saturday with warm temperatures and increasing rain throughout the day. Look for increasing signs of surface snow instability and avoid terrain traps where even a small but heavy wet snow avalanche could be dangerous. Expect quickly escalating avalanche danger Saturday afternoon and evening.
Detailed Forecast
A warm and moist frontal system will impact the Pacific Northwest over the weekend. Light rain and snow should begin in the Olympics Saturday morning and become heavy in the afternoon along with increasing southwest winds. Precipitation will be especially heavy on the W-SW slopes of the Olympics.Â
Steep slopes that recently received snowfall should be primed for wet loose avalanches, especially when loaded with rain Saturday. Natural pinwheeling of surface snow is usually a precursor to this type of avalanche. Expect wet loose avalanches to potentially entrain moist and unconsolidated snow (former storm slab) near and below treeline and could make for a large and destructive wet snow avalanche in specific areas. If you are sinking in more than ankle deep, expect wet loose avalanches to be possible on steeper slopes. With the continuing warm temperatures, cornices are still expected to be sensitive so give them a wide berth when traveling along ridgelines.Â
Cornices have grown large over the last several weeks will continue to be weakened by the rain and warm temperatures. Â We suggest you give cornices a wide berth and avoid travel on slopes with large cornices overhead.Â
The north Cascades and Olympics have a higher danger related to more quickly escalating avalanche danger Saturday. The avalanche forecast is for the daylight hours (through 6 pm) but deteriorating avalanche conditions are expected Saturday night with natural avalanches becoming likely as heavy rain increases and loads recently formed storm slabs.Â
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Snowpack Discussion
Recent Weather
A very active two week storm cycle ended 2/25. This cycle produced about 9 feet of snowfall and produced many avalanches near the Hurricane Ridge area.
Warm and mainly dry weather at the end of February led to wet snow avalanches and melt/freeze crusts at Hurricane Ridge and throughout the region.Â
A series of storms began Sunday March 2nd and have been moving through daily over the past six days and finally ended Friday morning. There has been about 5 inches of water and 1-2 feet of new snow deposited at Hurricane Ridge during this period as the snow level has reached 6000 feet at times.  Â
Hurricane Ridge
Last Saturday, a NPS ranger and observer Tyler Reid reported a very hard surface crust had formed as a result of the significantly colder overnight and early morning temperatures.
The latest storm cycle that began on Sunday likely produced an avalanche cycle at Hurricane Ridge similar to the Cascades Sunday night and Monday morning.  Though no first hand observations have been made, poor bonds to the melt-freeze crust from late last week will likely have provided bed surfaces and weak layers for storm slab failures. Snow levels have been rising and temperatures warming with increasing instability and avalanches similar to the Cascades on Tuesday afternoon and again Wednesday.
On Thursday heavy rain and snow continued, likely causing additional wet snow avalanches near and below treeline. A couple of inches of wet snow were recorded through 4 PM Thursday at the NWAC site.Â
NWAC observer Tyler Reid noted a thin melt-freeze crust on all aspects Friday mid-day and he also noted natural loose wet slides up to size D2 along with a natural cornice release on a NE aspect.Â
The mid and base pack around Hurricane Ridge should still consist of stable crusts and melt form layers from periods of warm weather earlier this winter. Also in the below tree-line zone on solar aspects rain and mild temperatures may keep the shallow snowpack wet and unconsolidated.Â
Avalanche Problems
Loose Wet
Release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Several loose wet avalanches, and lots of pinwheels and roller balls.
Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 2
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind lips of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
Cornices can never be trusted and avoiding them is necessary for safe backcountry travel. Stay well back from ridgeline areas with cornices. They often overhang the ridge edge can be triggered remotely. Avoid areas underneath cornices. Even small Cornice Fall can trigger a larger avalanche and large Cornice Fall can easily crush a human. Periods of significant temperature warm-up are times to be particularly aware.
A corniced ridgeline. A large cornice has formed at the top of the ridge. A smaller cornice has formed to the left of the trees from crossloading.
Cornices are easy to identify and are confined to lee and cross-loaded ridges, sub-ridges, and sharp convexities. They are easiest to trigger during periods of rapid growth (new snow and wind), rapid warming, and during rain-on-snow events. Cornices often catch people by surprise when they break farther back onto flatter areas than expected.
Aspects: North, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1