Strong solar radiation and rising temperatures may elevate hazard and could trigger natural avalanche activity on south facing slopes during the day.
Weather Forecast
A ridge of high pressure will dominate conditions for Tuesday and Wednesday before breaking down on Thursday. There is some wx model uncertainty regarding freezing levelsTuesday: Mostly sunny, freezing level 500-800m overnight, 1300-1500m afternoon, ridgetop winds light W-NWWednesday: A mix of sun and cloud, freezing level 500-1000m overnight, 1500-2000m afternoon, ridgetop winds 20-40 km/h SWThursday: A mix of sun and cloud, freezing level 800-1200m overnight, 1500-1800m afternoon, ridgetop winds light SW
Avalanche Summary
Widespread natural and human-triggered avalanche activity was reported on Sunday. This was primarily storm slabs and wind slabs associated with the storm on the weekend. Also reported was some wet snow activity at lower elevations where rain occurred.Early reports from Monday suggest less avalanche activity. Sluffing is reported from steep, rocky features on solar aspects triggered by the sun.
Snowpack Summary
The weekend storm produced 30-50 cm of dense snow with strong southerly ridgetop winds. The freezing level peaked around 1700 m, meaning low elevation terrain saw significant rain. Expect to find a crust at or near the surface below treeline. The early March melt-freeze crust is now down roughly 90-150 cm. This layer was found on all aspects at treeline and below, and on all but North aspects in the alpine. There are no new snowpack tests on this layer to report, but the continued loading and mild temperatures should help this weakness heal. The mid February crust/facet combo is generally buried quite deep (150 cm+), but there is still some potential for triggering this weakness with large loads in areas with thin or variable snowpack. We're thinking rocky north-facing alpine slopes. Lastly, cornices have grown large during the past few weeks. Give them a wide berth, especially if temperatures are mild or the sun is out.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
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.