Regions
Northwest Coastal.
Conservative route selection is essential now. Wind slabs, and cornices are prime concerns these days. Pay close attention to temperatures and solar input while riding in the back country.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
The Northwest Coastal will see light precipitation in advance of a ridge of high pressure that will bring clear skies and warm temperatures. MONDAY: Freezing level dropping to 600 m overnight, then beginning to rise to 1500 m by midnight. Winds begin to change from west to north west with no significant precipitation in the forecast for Monday. TUESDAY: Freezing level around 2500 m early in the day then begin a slow but steady rise to end the day around 3000 m. No precipitation on Tuesday and light to moderate north west winds. WEDNESDAY: The freezing level continues to rise, topping off the day at 3500m, with winds from the north and no precipitation. The day should be sunny with a bit of valley fog early in the day.
Avalanche Summary
A few storm slab avalanches up to size 1.5 on north and north east aspects above 1400m triggered by explosives and 2 skier controlled size 1 wind-slabs. Pay close attention to warming and solar radiation as the high pressure system moves into the area and spring heats up.
Snowpack Summary
5 to 10 cm of storm snow has fallen at higher elevations recently. At treeline and in the alpine small wind slabs will have formed. These wind slabs overlie a variety of surfaces which include a hard crust on solar aspects above 1300 m, moist or refrozen snow on all aspects below 1300 m. A layer of surface hoar from March 25th has been noted buried under 15 to 20 cm of storm snow and resting on a melt freeze crust. . A more widespread crust/facet layer buried in early February can now be found down over a metre. Both of these layers have the potential for large avalanches especially with a large trigger such as a cornice fall. Be cautious during periods of warming and intense solar radiation. As the winds from the incoming high pressure system change from west to north, the potential for reverse loading will exist, wind slabs may form on south slopes rather than north slopes, stay attuned to what the wind is doing!
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.
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.