Regions
Northwest Inland.
Rapid warming make push the hazard higher than forecast. Conservative terrain choices are the best bet these days.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
The snowfall from this weekend will taper off with a few scattered flurries on Monday morning, but nothing significant as far as precipitation goes. A high pressure ridge is forecast to be the big news in the weather pattern for next week. MONDAY: Freezing level dropping to 700 m overnight, then beginning to rise to 1500 m by midday. No precipitation in the forecast, winds forecast to be light to moderate from the northwest. TUESDAY: Freezing level starts at 2200m early Tuesday morning, then begins to rise reaching 3000 m by early Tuesday evening. Light to moderate winds mostly from the north west, no precipitation in the forecast. WEDNESDAY: Clearing skies and freezing level climbing to 3300m. Winds from the north west, no precipitation forecast.
Avalanche Summary
Few reports of avalanches from yesterday but are more likely the result of poor visibility rather than lack of activity. Cornices, soft storm slabs and wind slabs at higher elevations, loose-wet avalanches as the spring sun comes,... out are the prime concerns these days.
Snowpack Summary
At treeline and above small wind slabs overly a variety of surfaces include crust on solar aspects above 1300 m, moist or refrozen snow on all aspects below 1300 m, and settled wind slabs in exposed high elevation terrain. Surface hoar from March 23rd is still being mentioned in the northern half of the region, and now may be covered by up to 20cm of recent storm snow. Professional operators are tracking two deep weak layers from early-January and February that are now down about 1 meter or more. These layers are generally dormant but might wake up with increased warming or a heavy trigger (like a cornice fall). Basal facets exist in some areas and have been shown to be reactive in the north of the region. Rapid warming may wake up deeply buried weak layers.
Problems
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.
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 drifts 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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.