Regions
Northwest Coastal.
Confidence
Fair - Intensity of incoming weather is uncertain on Friday
Weather Forecast
A low pressure system over the Gulf of Alaska is moving a strong Westerly flow through the forecast period. This will bring a mix of frontal systems, and ridges. These fast moving systems will be hard to time, and they'll bring light-moderate amounts of precipitation accompanied by periods of clearing and sunshine. A building ridge will develop Friday through the weekend. Dry conditions, warming temperatures, and intense solar radiation may persist. Moderate precipitation expected in the evening (10-15 mm). Ridgetop winds moderate from the SE. Freezing levels 140 m. Friday: Moderate- heavy (25 mm) during the day. Ridgetop winds light-moderate from the SW. Freezing levels steady 700 m. Saturday: Dry, skies clearing. Ridgetop winds light from the SE. Freezing levels rising to 1200 m.
Avalanche Summary
On Tuesday a large explosive control mission reported 10 size 2-2.5, and 1 size 3 avalanches. Slopes targeted were E-SE, 1500 m and below. On Monday, numerous natural glide avalanches were reported up to size 3. Several loose wet avalanches up to size 2.5 that ran to ground have also been observed in response to warming from rainfall and sunshine.
Snowpack Summary
Spring-like conditions exist through the region. Melt and frozen surfaces continue on all aspects. Slopes that start to become wet, and slushy should be avoided because loose wet avalanches may occur. Lately, a lack of consistent overnight freezing has left the snowpack weak and unconsolidated, even isothermal below 1100 m, although some re-freezing has been reported in some areas. Glide cracks have opened up and pose the threat of large, full-depth releases, especially on steep rocky terrain features at low elevations. Large cornices loom, and ice cliffs pose a threat from above. For more information on Spring Conditions and ways to mitigate risk, please visit the new Forecasters Blog Post.
Problems
Loose Wet
Loose Wet avalanches are the 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. 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.
Wet Slabs
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.