Confidence
Fair - Timing or intensity of solar radiation is uncertain for the entire period
Weather Forecast
A stagnant weather pattern dominated by a ridge of high pressure brings increasingly sunny periods with benign convective cloud over the holiday weekend. Saturday: Freezing level starts at the surface, climbs to 1800 m, then returns to the surface overnight. Ridge top winds light out of the west, gusting to moderate in the afternoon. Sunday: Flow switches from north to south late in the day allowing freezing levels to climb all the way to 2000 m. Winds light East, switching S, SE Sunday night. Monday: Winds light S. Freezing level starts around 1000 m, climbs to 2000 m in the afternoon.
Avalanche Summary
Control work Thursday produced touchy soft slab avalanches up to size 2 that were intentionally triggered by both skiers and explosives. Widespread sluffing out of steep terrain was also observed. The sun came out in parts of the region Friday which no doubt initiated some avalanche activity. Avalanches releasing on the deeply buried mid-February surface hoar are becoming less likely. Avalanches may step down to the weak layer of facets or depth hoar on a crust that was buried in October. There was another report of a skier who propagated a size 3.0 avalanche on the weekend near Golden; the skier was fully buried and quickly rescued by their companions (the incident is attached to this bulletin).
Snowpack Summary
Wednesday's system produced around 40 cm of new snow in the north & 25 cm in the south. This snow was accompanied by light NW winds that formed very soft slabs in wind exposed terrain. The recent storms have added up to about a 125 cm of snow in the region. High freezing levels have consolidated this snow into a cohesive slab that may be propagated remotely. 125 cm now rests on top of a sun crust that was buried on March 27th on southerly aspects, and above wind affected surfaces that may be facetted on northerly aspects. Operators are reporting moderate shears on this interface. Cornices are reported to be very large and exist on most ridge lines. The mid-pack is well settled and strong. There is a weak layer of facets or depth hoar in shallower snowpack areas that may fail with initial warming of the snowpack. There is also a weak layer of of facets or depth hoar above a crust at higher elevations where there was already snow in October.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.
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.