Regions
Vancouver Island.
Confidence
Moderate - Lots of field data and weather models in agreement, but evidence of anomalous avalanche activity exists.
Travel & Terrain Advice
Spring diurnal cycles are in effect and have been creating rapid destabilization to the upper snowpack in the mid afternoon. Pay special attention to the temperatures and the changes to the upper snow (going slushy) and avoid exposure to terrain traps during these times. Even small loose wet avalanches have a surprisingly pushy nature. Late Thursday’s rain below treeline will add even more warmth and moisture to an already loose snow surface. A cooling trend begins as we move into the weekend with potential for new snow Sunday. At this time quantities look light to moderate, but keep a eye on how much falls and adjust your travel choices accordingly.
Avalanche Summary
Avalanche control at Mt Washington has produced only loose wet sluffing in the afternoon warmth, up to size 1 on steep, unsupported slopes all aspects treeline and below, even on previously non skied aggressive terrain just out of bounds.A skier accidental was reported on Wednesday afternoon. The avalanche was a hefty 1.5 on a NE asp at 1400 m in the Mt Adrian area. The wind slab was on a 40 degree slope and fractured 10-40 cm down on possibly the March 22 crust. 3 people were involved, no burial, no injuries and no loss of gear.The sea to sky avalanche region (our nearest reporting neighbour) has seen numerous skier accidental and skier remote avalanches size 2-3 on their March 21 crust layer, with unfortunately a fatality reported Wednesday.
Snowpack Summary
2- 8 cm of new moist snow now lies on top of a variable support crust from last week. This caps approx 10-12 cm of snow that (in tests) shows a strong bond to the March 22 crust. Tests producing only hard results (PC) on top of the March 22 crust. All of the upper snowpack is moist due to the significant warm temps, with freezing levels riding at treeline and even rising up in to the alpine elevations throughout the entire forecast region. N-E slopes near ridge top at treeline and in the alpine have lingering windslabs approx 10-40 cm thick. Seams quite stable……. However, evidence presented by the skier accidentals (both on the island and the more widespread results in the sea to sky region) seams to hint to the possibility of lingering isolated zones of buried surface hoar lurking above the March 22 crust. Whether this island skier accidental was an anomalous avalanche or that testing in other island regions has just failed to locate this layer, leads to some trepidation to let it all hang out there this weekend. Locating this buried weak layer under lingering windslabs might prove more difficult than finding any left over chocolate Easter eggs after a herd of hungry children has passed through, but it would probably be a good idea to search for its presence before committing to any big slopes (especially in lee, wind sheltered, shady N-E zones at treeline and in the alpine). Though it may be a low probability avalanche problem, it could be a high consequence (deep and big) event.
Snowpack Details
Surface: 2-8 cm of new moist warm snow over a decomposing crust (crust 3-5 cm). Upper: 10-12 cm of moist warm snow bonding well (with exceptions??) to the March 22 decomposing crust. Mid: Well settled. Lower: Well settled.
Past Weather
A typical spring day Wednesday with cool overnight and warm afternoon temps and no new precip. 2-7 cm of new snow fell early Thursday as temperatures slowly increased into positive digits at treeline elevations around the region. Late in the day Thursday mixed precip and some light rain fell below treeline to the east. Winds were moderate to light from the SW.
Weather Forecast
Light to moderate precip (type and amount depend on elevation and location) Thursday night tapers off into Friday. Temps will begin to drop significantly over the weekend and the next potential light to moderate snow arrives Sunday. Friday: 2 to 9 mm precip, winds strong SW overnight falling to moderate to light during the day, temps 0 overnight dropping to -3 and then back to 0, freezing level 1400 to 1000 to 1400 m. Saturday: 0 to 1 mm precip, winds L SE to SW, temps 0 dropping to -4, freezing level 1000 to 1300 to 900 m. Sunday: 2 to 12 cm of new snow (larger quantities forecast for the north), winds moderate NW, temps -5 to -8, freezing level 400 to 900 to 500 m
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.
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.
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.