Regions
Northwest Coastal.
Avalanche hazard will likely increase throughout the day, be sure your plans allow for a safe retreat from the mountains.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Synopsis: A series of relatively weak systems should deliver daily precipitation through the weekend. There is potential for a very potent storm early next week, but its still way too early to count on.Wednesday Night: Precipitation: 2:7mm - 3:10cmThursday: Freezing Level: 700m - 1100m; Precipitation: 2:10mm - 2:15cm; Wind: Treeline: Moderate, S/SW | Ridgetop: Strong, SWFriday: Freezing Level: 800m - 1200m Precipitation: Trace; Wind: Treeline: Light, SW | Ridgetop: Moderate, WSaturday: Freezing Level: 1100m - 1400m; Precipitation: 1:8mm - 2:13cm; Wind: Treeline: Light, S | Ridgetop: Strong, SW
Avalanche Summary
On Tuesday there was one report of a remotely triggered size 2 wind slab avalanche on a NE facing aspect at 1500m. This location had previously slid on the early February crust/facet/surface hoar combo. Isolated loose wet avalanches to size 1.5 were also reported from steep southerly terrain.On Monday. A large rock fall event initiated a size 3.5 avalanche that failed on the early February persistent weak layer. Several smaller loose snow avalanches to size 2 were running in the recent storm snow on steep solar aspects too.
Snowpack Summary
It's starting to feel like spring in the NW. Valley temps are creeping into the double digits during the day, and there are reports of the top 15 cm of the snowpack becoming moist during daytime heating.The last significant shot of snow was on March 27th, 10 - 15 fell on March 30th. This new snow rests on top of a haggard old surface composed of old wind slab, melt freeze crust, and faceted old snow. Ongoing melt freeze cycles will likely help to heal any surface instabilities.The early March layer can be found down 75 - 100cm and is composed of facets/surface hoar on shady aspects and facets/crust on southerly aspects. I suspect this layer has been the culprit in the human triggered avalanches from March 27/28 that are being reported on the Balktalk Facebook Page.The early February crust/facet/surface hoar combo is down 150 - 200cm, and I suspect it's gone mostly dormant for now.
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.
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.